DCS dCS 974 User Manual

© 2001 dCS Ltd

dCS 974

Digital to Digital Converter

User Manual

Software version 1.0x

May 2001

All rights reserved. Reproduction of this manual in any manner whatsoever,
without the written permission of dCS
this manual may be obtained from dCS.

Information contained in this manual is subject to change without notice, and
whilst it is checked for accuracy, no liabilities can be accepted for errors.

1

Ltd is Data Conversion Systems Ltd. Company registered in the England no. 2072115

dCS

1

is strictly forbidden. Additional copies of

dCS 974 User Manual Manual for Software Version 1.0x
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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

RODUCT OVERVIEW

P

The dCS 974 DDC (Digital to Digital Converter) is a high performance real time
sample rate and format converter, developed from our highly successful
dCS 972. It is designed for studio applications where source material is available
in one format, but outputs are required in other digital formats in real time. For
example, archives might be made for storage in 24/192 or 24/176.4 formats,
and then used to produce output in SACD, DVD, CD and other multimedia
formats. AES3, SPDIF, SDIF-2 and DSD formats are all supported, and multiple
units may be synchronised for stable multi-channel operation.

The unit is mains powered and is housed in a 2U (3.5”) high 19” rack mounting
case. It may be controlled either from its front panel, or from a software based
remote control running on a PC. Frequently used Setups may be stored and re­called later. The last setting is automatically stored on power down, so that fixed
installations may be set up at leisure, installed and then left alone. Unauthorised
alterations to settings may be prevented by a “panel lock out” feature.

Numerous monitoring functions are provided – both for the audio signal and for
messaging attached to it. The unit has bit activity and level meters, and
message manipulation. CRC, parity and invalid errors may be monitored and
reported, so that “right first time” transfer to disc plants may easily be achieved.

Formats

Functions

The unit is highly software based, and more functions and features are added
from time to time. Software updates from dCS are free!

2

• DSD at 2.822MS/s (see page 71)

• PCM from 192 kS/s down to 11.025 kS/s (see page 43)

• PCM data formats supported are: AES/EBU (XLR), Dual (2 wire) AES3

(XLR), Quad (4 wire) AES3 (XLR), SPDIF (Phono, Toslink and BNC) and
SDIF-2 (see page 70)

• DSD data formats supported are SDIF-2 (BNC), SDIF-3 (BNC) and DSD

Quad (4 wire - XLR)

• Sample Rate and Format Conversion (page 34)

• Multi-channel Sync capability (page 42)

• Bit for bit multiplex/de-multiplex mode (page 39)

• PCM to DSD, DSD to PCM

• DC Removal for DSD

• Multiple filters on many major sample rate conversions (page 45)

• Dither – 3 types (see page 47)

• Noise shaping – 10 different options on all major PCM sample rates (page

47).

• Output Level control with “Maximise” (page 48)

• Balance control (page 48).

• Digital Silence out with digital silence in (page 50)

Syncing

Comprehensive - can sync to Wordclock or AES reference, or signal, and sync
to video option available.

2

free if we email them, and you download from a PC COM port. Low cost if you ask us for EPROMs or other

media - we charge for media and handling.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Monitoring

Bit Activity (page 56), Stereo Output Level (page 57), and CRC, Parity & Invalid
flag errors in the input data (page 52).

Test Generator

High quality (160 dB) signal generator with mHz resolution (page 53). Can be
dithered and/or noise shaped truncated.

Ease of Use

User programmable set-ups (page 61)
Pre-loaded setups
Remembers last settings
Lockouts (page 64)

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

About this Manual

If you have not used a dCS 974 before, please read the section Using Your

dCS 974 For The First Time on page 110.

This manual has been arranged with the most commonly used sections placed
first:

• table of contents (page 6)

• step-by-step (page 10) and applications guides (page 22)

• detailed software and hardware information (page 34)

• technical information (page 70)

• information for first time users (page 110)

• options, maintenance and troubleshooting (page 114)

• index section (page 124)

References to other sections in the text have the Section Name, page … with

Section Name in bold. Sometimes, if you are reading a soft copy of the manual,

section names and page numbers are hyperlinks – click on them, and you will
go there.

IMPORTANT!

The manual is designed to be helpful. If there are points you feel we could cover
better, or that we have missed out - please tell us.

About Sample Rates

All references to sample rates in this manual use the unit kS/s (kilo Samples per
second) rather than the technically incorrect kHz.

Important information is presented like this - ignoring this may cause you to
damage the unit, or invalidate the warranty.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

ONTENTS

C

Product Overview ...............................................................................................3

About this Manual 5
About Sample Rates 5

Contents ..............................................................................................................6

Step-by-Step Guide ..........................................................................................10

Preliminaries 10
Step 1 – Selecting an Input 11

Connecting to a Single AES or SPDIF source 11
Connecting to a PCM SDIF-2 source 11
Connecting to a Dual AES Source 12
Connecting to a Quad AES source 12
Connecting to a DSD SDIF-2 source 12
Connecting to a DSD Quad source 12

Step 2 – Setting the Sync Source 13

Syncing to an External Wordclock 13
Syncing to an AES/EBU Reference 14

Step 3 - Setting a Conversion 15

Format Conversion 15
Sample Rate Conversion 16

Step 4 – Connecting the Outputs 18

Connecting a Single AES or SPDIF Output 18
Connecting the SDIF-2 Output 18
Connecting the Dual AES Outputs 18
Connecting the Quad AES or DSD Quad Outputs 18
Connecting the DSD SDIF-2 or DSD SDIF-3 Output 18

Step 5 – Reducing the Output Wordlength 19

Other Settings 21

Typical Applications.........................................................................................22

Converting a 24/96 recording to CD format 22
Demultiplexing a 24/96 Dual AES recording (Bit for Bit) 23
Upsampling a CD 24
General Sample Rate Conversion and Distribution 25
PCM to DSD 26
Using a Master Clock 27
Converting Quad AES to CD Format 28
Multi-channel Sample Rate Conversion – bit aligned sources 29
Multi-channel Sample Rate Conversion – Using a Master Clock 30
Multi-channel Sample Rate Conversion – with more alignment tolerance 31
Multi-channel Sample Rate Conversion – with multiple sample rates out 32

The Software – Menu and Setups ...................................................................34

Navigating through the Menu – what the On-Screen symbols mean 36
Top Menu 38

Sample Rate Conversion 38
Format Conversion 39
Error Monitoring 39
Test 39
Info 39
Bit Activity Monitors 40
Level Meters 40
Display 40

Sample Rate Conversion / Format Conversion Submenu 41

Audio Input Select 41
Sync Source 41
Multiple Channel Sync 42
Input Sample Rate 43
Output Sample Rate 43
Output Mode 45
Filter 45
Output Word Length 46

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dCS 974 User Manual Manual for Software Version 1.0x
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Noise Shaping 47
Dither 47
AES Message Edit 48
SPDIF Message Edit 48
Gain/Balance and Maximise 48
Swap Channels 49
Phase 49
Detect Silence 50
De/Pre-Emphasis 50
Display Customise 50

Error Monitor Submenu 52

Error Hold and Reset 52

Test Submenu 53

Generator Overview 53
Controlling the Generator 53
Generator Amplitude Adjustment 54
Generator Frequency Adjustment 54

Self Test 55
Info Submenu 56
Bit Activity Monitor Submenu 56

Bit Activity Monitoring Overview 56

Setting the Monitor 56
Level Meters Submenu 57

Level Meter Overview 57

Turning the Level Meters On 57

Meter Type (Bar or Numerical) 58

Decay Time 58

Peak Hold 58

Using the dCS 974 to monitor a track 59

Watch Out for this One! 59
Display Submenu 60
Setups and Locking the Front Panel 61

Storing a Setup 61

Fixed Setups 63

Recalling a Setup 63

Locking Out Changes, and Unlocking Again 64

The Hardware – Controls and Connectors ....................................................66

Rear Panel 66

Signal Inputs 66

Signal Outputs 67

Control and Power 67

Additional Information 67
Front Panel 68

Power Indicator 68

OPERATION buttons 68

MEMORY buttons 68

LCD display 68

LED indicators 69

Rotary encoder 69

dCS 974 Technical Information.........................................................................70

Digital Data Formats Supported 70
DSD 71
PCM Input and/or Output Performance 73
Clocking 76
Sample Alignment 77
Multiple Channel Sync’ing 81

Multiple Channel Multiple Sample Rate Synchronising 83
Noise Shaping 84
Dither 85
Digital Interface Specifications 86
Message Handling 88

AES/EBU Message Handling 88

SPDIF Message Handling 89

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dCS 974 User Manual Manual for Software Version 1.0x
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SDIF-2 Message Handling 90

SDIF-3 Message Handling 90
Power Consumption 91
Size, Weight and Operating Conditions 92

dCS 974 Performance Curves ...........................................................................94

General Technical Information......................................................................104

Word Length Reduction 104

Using Your dCS 974 For The First Time ........................................................110

What’s in the Box? 110
Supply Voltage Setting 110
Getting Started 110
Installing the Unit in a Rack 112

Options ............................................................................................................114

Locking to Video Sample Rates 114
Mains Supply Voltage 114
Ordering Options for a New Unit 114
Having Your Options Changed 114

Maintenance and Support..............................................................................116

Hardware 116

Service & Maintenance 116

User Changeable Parts 116
Software 117

Installing New Software 117
Warranty 118

Initial Warranty 118

Extended Warranty 118

Warranty Exclusions 118

Obtaining Service 118
Update or Calibration 119
Safety and Electrical Safety 119

Troubleshooting .............................................................................................120

FAQs 120
If You Need More Help 123
Other Information 123

Indexes and Software Version Numbers......................................................124

Definitions of Units 124
Tables 124
Figures 125
Keywords and Phrases 126
Owner Registration Transfer 131

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

TEP-BY-STEP GUIDE

S

This section guides you through setting up the unit for basic operation. You may
find this useful if you have not used the dCS 974 for a while.

Preliminaries

The Quick Start Guide sheet details the menu structure and outlines the use of
the front panel controls. For more information, see Navigating through the

Menu – what the On-Screen symbols mean on page 36 and The Software –
Menu and Setups on page 34. We will be changing settings in either the

Sample Rate Conversion menu or the Format Conversion menu. Use the

rotary control to scroll up and down the screen and the Operation buttons to
change menu levels or select items.

Connect up with cables designed for digital audio:

• for AES/EBU interfaces use 110Ω screened, twisted pair cables fitted with

one male XLR connector and one female XLR connector.

• for DSD/SDIF or SPDIF BNC interfaces, use 75Ω coax cables fitted with

BNC plugs.

• for SPDIF RCA interfaces, use 75Ω coax cables fitted with RCA Phono

plugs.

• for SPDIF TOS interfaces, use Toslink fibre-optic cables.

Power up the unit and wait for about 20 seconds while it configures itself. The
screen will show:

Press the Recall button. When the screen displays the Recall Setup list, press
the Recall button again to change to the preset setup list, then press the Enter
button. Wait while the unit loads the default setup (Store A) then displays a

Status screen similar to this:

The Power and Unlocked indicators should be lit, the other indicators should
be off.

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dCS 974 User Manual Manual for Software Version 1.0x
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Step 1 – Selecting an Input

TOP LEVEL

Sample Rate Conversion

Audio Input Select AES 1 Default

Sync Source AES 2

Multi-Channel Sync AES 3

Input Sample Rate AES 4

Dual AES (1+2)

Quad AES

SPDIF1 (RCA)

SPDIF2 (BNC

SPDIF3 (TOS)

PCM SDIF-2
DSD SDIF-2

DSD Quad

Figure 1 – Audio Input Selection

Choose one of the following five sections:

Connecting to a Single AES or SPDIF source

do this: Connect your source equipment to the matching input on the dCS 974 rear panel

using suitable cables. An AES3 source (XLR connector) may be connected to
any of the four AES/EBU inputs.

do this: Press the →→→→ button twice to enter first the Sample Rate Conversion menu,

then the Audio Input Select menu. Use the rotary control to scroll down the list
until the cursor is beside your chosen input (either AES 1, AES 2, AES 3, AES 4,

SPDIF 1 (RCA), SPDIF2 (BNC) or SPDIF3 (Toslink)). Press the Set button.

The screen will change back to the Sample Rate Conversion menu. Proceed
to Step 2.

Connecting to a PCM SDIF-2 source

do this: Connect the SDIF-2 output on your source equipment to the upper block of

DSD/SDIF connectors on the dCS 974 rear panel using 3 coax cables. Connect
CH1 out to CH1 IN, CH2 out to CH2 IN, CLK out to WCLK IN. Fit a 75Ω
terminating plug to the nearby LOOP OUT connector.

do this: Press the →→→→ button twice to enter first the Sample Rate Conversion menu,

then the Audio Input Select menu. Use the rotary control to scroll down the list
until the cursor is beside PCM SDIF-2. Press the Set button to select it.

The screen will change back to the Sample Rate Conversion menu. Proceed

to Step 2.

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dCS 974 User Manual Manual for Software Version 1.0x
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Connecting to a Dual AES Source

do this: Check that your source equipment is capable of Dual AES operation.
do this: Connect the AES 1 (or AES A) output on your source equipment to the AES 1

input on the dCS 974 rear panel and the AES 2 (or AES B) output to the AES 2
input, using two XLR cables. Ensure the cables are not swapped.

do this: Press the →→→→ button twice to enter first the Sample Rate Conversion menu,

then the Audio Input Select menu. Use the rotary control to scroll down the list
until the cursor is beside Dual AES. Press the Set button to select it.

The screen will change back to the Sample Rate Conversion menu. Proceed

to Step 2.

Connecting to a Quad AES source

do this: Check that your source equipment is capable of Quad AES operation.
do this: Connect the AES 1 output on your source equipment to the AES 1 input on the

dCS 974 rear panel, the AES 2 output to the AES 2 input, the AES 3 output to
the AES 3 input and the AES 4 output to the AES 4 input, using four XLR
cables. Ensure the cables are connected in the correct order.

do this: Press the →→→→ button twice to enter first the Sample Rate Conversion menu,

then the Audio Input Select menu. Use the rotary control to scroll down the list
until the cursor is beside Quad AES. Press the Set button to select it.

The screen will change back to the Sample Rate Conversion menu. Proceed

to Step 2.

Connecting to a DSD SDIF-2 source

do this: Check that your source equipment is capable of DSD-SDIF operation.
do this: Connect the DSD SDIF-2 output on your source equipment to the upper block

of DSD/SDIF connectors on the dCS 974 rear panel using three coax cables.
Connect CH1 out to CH1 IN, CH2 out to CH2 IN and CLK out to WCLK IN. Fit a

75Ω BNC terminating plug to the nearby LOOP OUT connector.

do this: Press the →→→→ button twice to enter first the Sample Rate Conversion menu,

then the Audio Input Select menu. Use the rotary control to scroll down the list
until the cursor is beside DSD SDIF-2. Press the Set button to select it.

There will be a noticeable delay while the DSD code loads, then the screen will
change back to the Sample Rate Conversion menu. The dCS 974 will

automatically detect either SDIF-2 or SDIF-3. Proceed to Step 2.

Connecting to a DSD Quad source

do this: Check that your source equipment is capable of DSD Quad operation.
do this: Connect the AES 1 output on your source equipment to the AES 1 input on the

dCS 974 rear panel, the AES 2 output to the AES 2 input, the AES 3 output to
the AES 3 input and the AES 4 output to the AES 4 input, using four XLR
cables. Ensure the cables are connected in the correct order.

do this: Press the →→→→ button twice to enter first the Sample Rate Conversion menu,

then the Audio Input Select menu. Use the rotary control to scroll down the list
until the cursor is beside DSD Quad. Press the Set button to select it.

There will be a noticeable delay while the DSD code loads, then the screen will
change back to the Sample Rate Conversion menu. Proceed to Step 2.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Step 2 – Setting the Sync Source

do this: Switch on the source equipment. If appropriate, load a disk / tape and set the

machine in PLAY mode to ensure it is generating a digital audio data stream.

The dCS 974 will be set to sync to the selected Audio Input and the Input

Sample Rate will be Auto detected. The unit should lock and the Unlocked

indicator should turn off. If you do not want to use an external reference clock,

proceed to Step 3.

TOP LEVEL

Sample Rate Conversion

Audio Input Select

Sync Source Audio Input Default

Multi-Channel Sync AES Loop

Input Sample Rate AES Loop Term

Wordclock

Internal

Lab Ref (10MHz)

Figure 2 – Sync Source Selection

If a stable clock source is available, you can reduce jitter in your system by
syncing to it. Choose one of the following two sections:

Syncing to an External Wordclock

If you want to synchronise your system to Wordclock from a Master Clock (such
as the dCS 992) or other stable source, do the following:

do this: Set the Master Clock sample rate to match the source (probably 44.1 or

48kS/s).

do this: Connect either a Wordclock or AES/EBU output from the Master Clock to the

clock input on the source equipment and ensure it is locked.

do this: Connect another Wordclock output from the Master Clock to the WCLK IN

connector (upper block of DSD/SDIF connectors) on the dCS 974 rear panel. Fit
a 75Ω BNC terminating plug to the nearby LOOP OUT connector.

If the source equipment uses SDIF-2 (in either PCM or DSD mode), the
Wordclock feed from the Master Clock replaces the Wordclock feed from the
source equipment.

do this: Scroll down the Sample Rate Conversion menu to Sync Source and press

the →→→→ button. Scroll down the list to Wordclock and press Set.

The Unlocked indicator will light for a few seconds, then turn off as the unit re­locks.

do this: Proceed to Step 3.

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dCS 974 User Manual Manual for Software Version 1.0x
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Syncing to an AES/EBU Reference

If you want to synchronise your system to an AES/EBU Reference from a
Master Clock (such as the dCS 992) or other stable source, do the following:

do this: Set the Master Clock sample rate to match the source (probably 44.1 or

48kS/s).

do this: Connect either an AES/EBU or Wordclock output from the Master Clock to the

clock input on the source equipment and ensure it is locked.

do this: Connect another AES/EBU output from the Master Clock to the AES Ref Loop

IN connector on the dCS 974 rear panel.

do this: Scroll down the Sample Rate Conversion menu to Sync Source and press

the →→→→ button. Scroll down the list to AES Loop Terminated and press Set.

The Unlocked indicator will light for a few seconds, then turn off as the unit
re-locks.

do this: Proceed to Step 3.

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dCS 974 User Manual Manual for Software Version 1.0x
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Step 3 - Setting a Conversion

do this: If you need bit-for-bit operation in a different output format, proceed to the

Format Conversion section.

do this: If you want to change the sample rate or the word length or process the data in

some other way, proceed to the Sample Rate Conversion section.

Format Conversion

TOP LEVEL

Format Conversion

Pure Format Conversion Off Default

Audio Input Select On

Sync Source

Multi-Channel Sync

Input Sample Rate

Output Mode Normal Default

Display Customise Dual AES

Quad AES
DSD SDIF-2
DSD SDIF-3

Figure 3 – Pure Format Conversion

do this: Press the ←←←← button, scroll down to Format Conversion , press the →→→→ button

and press the Set button. This sets Pure Format Conversion to On and
disables the Sample Rate Conversion menu.

do this: If the “Fs In not Fs Out” information box appears on the display, press the Set

button to make the Output Sample Rate match the Input Sample Rate.

do this: Scroll down the Format Conversion menu to Output Mode and press the →→→→

button. The cursor should be beside Normal. Choose one of the settings from
the following list, scroll to it and press Set:

• Normal. The Input & Output Sample Rate must not be higher than

96kS/s. Bit-for-bit data will be available on all of the AES, SPDIF or SDIF-2
outputs.

• Dual AES. The Input & Output Sample Rate must be 88.2, 96, 176.4 or

192kS/s. Dual AES bit-for-bit data will be available on the AES 1 / AES 2
output pair and the AES 3 / AES 4 output pair. Do not use the other outputs.

• Quad AES. The Input & Output Sample Rate must be 176.4 or 192kS/s.

Quad AES bit-for-bit data will be available on the AES 1, AES 2, AES 3 and

AES 4 output group. Do not use the other outputs.

• DSD SDIF-2. The Audio Input Select setting must be DSD or DSD Quad.

DSD SDIF-2 bit-for-bit data will be available from the DSD/SDIF outputs
(lower block) and DSD Quad data from the AES 1, AES 2, AES 3 and AES

4 output group. Do not use the other outputs.

• DSD SDIF-3. The Audio Input Select setting must be DSD or DSD Quad.

DSD SDIF-3 bit-for-bit data will be available from the DSD/SDIF outputs
(lower block) and DSD Quad data from the AES 1, AES 2, AES 3 and AES

4 output group. Do not use the other outputs.

do this: Proceed to Step 4.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Sample Rate Conversion

TOP LEVEL

Sample Rate Conversion

Audio Input Select 192kS/s

Sync Source 176.4kS/s

Multi-Channel Sync ...

Input Sample Rate 12kS/s

Output Sample Rate 11.025kS/s

DSD Clock (DSD only)

Output Mode Normal Default

Filter Dual AES

Quad AES
DSD SDIF-2
DSD SDIF-3

Figure 4 – Sample Rate Conversion

do this: If DSD output formats are required, proceed to Setting the Output Mode.

Setting the Output Sample Rate

do this: If PCM outputs are required, scroll down the Sample Rate Conversion menu

to Output Sample Rate and press the →→→→ button. Scroll down the list to the
required rate and press the Set button.

If the selected conversion can be handled in one pass, the setting will be
accepted and the screen will change back to the Sample Rate Conversion

menu. If not, this information box will appear on the display:

do this: Press any button to display a list of valid output sample rates. Scroll down the

list to a suitable rate and press the Set button.

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dCS 974 User Manual Manual for Software Version 1.0x
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Setting the Output mode

do this: Scroll down the Sample Rate Conversion menu to Output Mode and press

the →→→→ button. The cursor should be beside Normal Choose one of the settings
from the following list, scroll to it and press Set:

• Normal. The Output Sample Rate must not be higher than 96kS/s. Single

wire data will be available on all of the AES, SPDIF or SDIF-2 outputs.

• Dual AES. The Output Sample Rate must be 88.2, 96, 176.4 or 192kS/s.

Dual AES data will be available on the AES 1 / AES 2 output pair and the

AES 3 / AES 4 output pair. Do not use the other outputs.

• Quad AES. The Output Sample Rate must be 176.4 or 192kS/s. Quad

AES data will be available on the AES 1, AES 2, AES 3 and AES 4 output
group. Do not use the other outputs.

• DSD SDIF-2. The input format must be DSD, DSD Quad or PCM at

44.1kS/s or more. DSD SDIF-2 data will be available from the DSD/SDIF
outputs (lower block) and DSD Quad data from the AES 1, AES 2, AE S 3
and AES 4 output group. Do not use the other outputs.

• DSD SDIF-3. The input format must be DSD, DSD Quad or PCM at

44.1kS/s or more. DSD SDIF-2 data will be available from the DSD/SDIF
outputs (lower block) and DSD Quad data from the AES 1, AES 2, AE S 3
and AES 4 output group. Do not use the other outputs.

do this: Proceed to Step 4.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Step 4 – Connecting the Outputs

Choose one of the following five sections:

Connecting a Single AES or SPDIF Output

do this: If the Output Sample Rate is 88.2 or 96kS/s, check that your destination

equipment is capable of double speed operation.

do this: If you have set Output Mode to Normal, connect the required single wire

output on the dCS 974 rear panel to the matching inputs on the destination
equipment using suitable cables. Signals are available from any of the four
AES/EBU outputs or the three SPDIF outputs simultaneously.

Connecting the SDIF-2 Output

do this: If the Output Sample Rate is 88.2 or 96kS/s, check that your destination

equipment is capable of double speed operation.

do this: If you have set Output Mode to Normal, connect the lower block of DSD/SDIF

connectors on the dCS 974 rear panel to the destination equipment using 3 coax
cables. Connect CH1 OUT to CH1 in, CH2 OUT to CH2 in and WCLK OUT to
CLK in.

Connecting the Dual AES Outputs

do this: Check that your destination equipment is capable of Dual AES operation.
do this: If you have set Output Mode to Dual AES, connect the AE S 1 output on the

dCS 974 rear panel to the AES 1 (or AES A) input on the destination equipment
and the AES 2 output to the AES 2 (or AES B) input, using two XLR cables.
Ensure the cables are not swapped. An identical Dual AES pair is available
from the AES 3 and AES 4 outputs.

Connecting the Quad AES or DSD Quad Outputs

do this: Check that your destination equipment is capable of Quad AES or DSD Quad

operation.

do this: If you have set Output Mode to Quad AES or DSD Quad, connect the AES 1

output on the dCS 974 rear panel to the AES 1 input on the destination
equipment, the AES 2 output to the AES 2 input, the AES 3 output to the AES 3
input and the AES 4 output to the AES 4 input, using four XLR cables. Ensure
the cables are not swapped.

Connecting the DSD SDIF-2 or DSD SDIF-3 Output

do this: Check that your destination equipment is capable of DSD operation.
do this: If you have set Output Mode to DSD SDIF-2 or DSD SDIF-3, connect the lower

block of DSD/SDIF connectors on the dCS 974 rear panel to the destination
equipment using three coax cables. Connect CH1 OUT to CH1 in, CH2 OUT to
CH2 in and WCLK OUT to CLK in.

Note that the default setting for the DSD output clock is 44.1kS/s Wordclock
(rather than Bit clock at 2.82MS/s).

do this: Proceed to Step 5.

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
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Step 5 – Reducing the Output Wordlength

If you are using Pure Format Conversion or DSD output modes, the Output
Wordlength cannot be changed. Proceed to Other Settings.

If you are performing a sample rate conversion with PCM outputs, the
destination equipment can handle 24 bit data and you do not want to reduce the
wordlength then leave the Output Wordlength set to the default of 24 bits and
set Dither to Off. Proceed to Other Settings.

The dCS 974 generates 24 bit data, regardless of the input word length. If the
destination equipment cannot handle 24 bit data, the Output Wordlength
MUST be set to match. Noise Shaping and/or Dither MUST be applied to
smooth the transitions. If the extra bits are just ignored, the audio outputs may
sound grainy and unpleasant low effects will result. For more information, see

Word Length Reduction on page 104.

do this: Check the maximum input wordlength specification in the manual for the

destination equipment. You must set the dCS 974 to match this.

TOP LEVEL

Sample Rate Conversion

Audio Input Select

Sync Source

Multi-Channel Sync

Input Sample Rate 24 Default

Output Sample Rate 23

Output Mode ...

Filter 8

Output Wordlength

Noise Shaping Off Default

Dither 1st Order

AES Message Edit ...

10th Order

Off Default

Top Hat

Triangular

NS Triangular

Figure 5 – Setting Wordlength, Noise Shaping and Dither

do this: Scroll down the Sample Rate Conversion menu to Output Wordlength and

press the →→→→ button. Scroll down the list to the required number of output bits
and press Set.

do this: Scroll down the Sample Rate Conversion menu to Noise Shaping and press

the →→→→ button. From the list below, choose a suitable setting to match the

Output Wordlength:

• for 22 or 23 bits, scroll to 2nd order and press Set.

• for 20 or 21 bits, scroll to 3rd order and press Set.

• for 16, 17, 18 or 19 bits, scroll to 9th order and press Set.

do this: For 16 or 17 bits, scroll down the Sample Rate Conversion menu to Dither

and press the →→→→ button. Scroll down to NS Triangular and press Set.

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A wide variety of Noise Shaping and Dither setting combinations are possible.
For more information, see Word Length Reduction on page 104.

do this: Proceed to Other Settings.

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
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Other Settings

The basic set-up procedure is complete. The Sample Rate Conversion menu
contains several other menu pages. For more information, see Sample Rate

Conversion / Format Conversion Submenu, starting on page 41.

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dCS 974 User Manual Manual for Software Version 1.0x
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YPICAL APPLICATIONS

T

Converting a 24/96 recording to CD format

From 24 bit /

96kS/s source

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

IN OUT

CH1 IN

RCA

BNC

TOS

WCLK IN

CH1 OUT

DSD / SDIF

LOOP IN

CH2 IN

LOOP OUT

CH2 OUT

WCLK OUT

REMOTE

IN

LOOP

OUT

MAINS FUSE (2AT) ON OF F

16 bit / 44.1kS/s from

4 independent AES outputs

16 bit / 44.1kS/s

from 3 independent

16 bit / 44.1kS/s

SDIF-2 output

SPDIF outputs

Figure 6 – Double Speed 24/96 to CD format

The dCS 974 converts a double speed 96 kS/s 24 bit AES input to a 44.1 kS/s
16 bit signal available from all of the 4 AES, 2 electrical SPDIF, optical SPDIF or
SDIF-2 outputs. The conversion set up uses Filter 2 (there is a choice of 4).
The SonicStudio™ uses 24/96 as double speed AES at the time of writing.

do this: Connect Sonic Solutions SonicStudio™ workstation AES output to AES 1 input

on the dCS 974.

do this: Load the setup from Store K, or use the settings below.
do this: Output from any AES output or any of the SPDIF outputs or, using two data

cables and one clock, via the SDIF-2 outputs.

Sample Rate Conversion settings:

Sample Rate Conversion: On
Audio Input Select: AES 1
Sync Source: Audio Input
Input Sample Rate: Auto (96 kS/s)
Output Sample Rate: 44.1 kS/s
Output Mode: Normal
Filter: Filter 2
Output Wordlength: 16
Noise Shaping: 9th Order
Dither: Off
Detect Silence: On
AES Message Edit: Professional Off, Non-Audio Off

Mode: Stereophonic

SPDIF Message Edit: Professional Off, Non-Audio Off, Copy

Permit On
Format: Compact Disc

Gain: -0.1dB

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Demultiplexing a 24/96 Dual AES recording (Bit for Bit)

From 24 bit / 96kS/s

Dual AES source

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

24 bit / 96kS/s from

4 independent AES outputs

Ensure AES 1 & AES 2
are connected correctly

AES / EBU INPUTS

AES / EBU OUTPUTS

AES 1 = Left data

AES 2 = Right data

AES / EBU REFERENCE LOOP SPDIF

IN OU T

AES CLK OUT SYNC INPUT

IN OUT

24 bit / 96kS/s

from 3 independent

SPDIF outputs

CH1 IN

CH2 IN

REMOTE

WCLK IN

CH1 OUT

LOOP IN

LOOP OUT

CH2 OUT

WCLK OUT

RCA

BNC

TOS

DSD / SDIF

IN

LOOP

OUT

MAINS FU SE (2AT) ON OFF

24 bit / 96kS/s
SDIF-2 output

Figure 7 – Converting dual AES 24/96 to a single wire double speed one

The dCS 974 converts a 96 kS/s 24 bit Dual AES input to a double speed
96 kS/s 24 bit signal available from any or all of the 4 AES, 2 electrical SPDIF,
optical SPDIF or SDIF-2 outputs. When using the Format Conversion menu,
the operation is bit for bit on the audio data (messages can be edited).

do this: Connect Nagra-D, Genex G-8000, SADIE, Lake DSP, etc dual AES source to

inputs AES 1 and AES 2 on the dCS 974.

do this: Load the setup from Store J and set Pure Format Conversion to On, or use

settings below.

do this: Output from any AES output or any of the SPDIF outputs or, using two data

cables and one clock, via the SDIF-2 outputs. The outputs will all be at “double”
speed.

Format Conversion settings:

Pure Format Conversion: On
Audio Input Select: Dual AES
Sync Source: Audio Input
Input Sample Rate: Auto (96 kS/s)
Output Sample Rate: 96 kS/s
Output Mode: Normal
AES Message Edit: Professional On, Non-Audio Off

Mode: Stereophonic

SPDIF Message Edit: Professional On, Non-Audio Off, Copy

Permit On
Format: 2-Ch Gen Format

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Upsampling a CD

DIGITAL OUT

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PU SH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

24 bit / 96kS/s (or 192kS/s)

Dual AES to DAC

CLOCK IN

16 bit / 44.1kS/s digital audi o

AES / EBU REFERENCE LOOP SPDIF

IN OU T

AES CLK OUT SYNC INPUT

L

R

IN OUT

Hand Crafted by

The Red Hot CD Player Co.

RCA

BNC

TOS

DSD / SDIF

CH1 IN

WCLK IN

CH1 OUT

LOOP IN

CH2 IN

LOOP OUT

CH2 OUT

WCLK OUT

REMOTE

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

Figure 8 – Upsampling a CD to 24/96 (or 24/192)

The dCS 974 converts a 44.1 kS/s 16 bit SPDIF input to a Dual AES 96 kS/s 24
bit signal available from AES 1 & AES 2 outputs. There is no information added
in the process, although you may wish to check theory here.

do this: Connect a source of CD material to the RCA input on the dCS 974.
do this: Enter the Sample Rate Conversion settings below.

do this: Connect Dual AES data from both AES 1 and AES 2 outputs to a DAC of your

choice.

do this: If your DAC is a dCS Elgar, dCS Delius or dCS 954, you can set the Output

Sample Rate to 192kS/s instead.

Sample Rate Conversion settings:

Sample Rate Conversion: On
Audio Input Select: SPDIF 1
Sync Source: Audio Input
Input Sample Rate: Auto (44.1 kS/s)
Output Sample Rate: 96 kS/s
Output Mode: Dual AES
Filter: Filter 2
Output Wordlength: 24
Noise Shaping: Off
Dither: Off
Detect Silence: Off
AES Message Edit: Professional On, Non-Audio Off,

Mode: Stereophonic

SPDIF Message Edit: Professional On, Non-Audio Off, Copy

Permit On
Format: 2-Ch Gen Format

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dCS 974 User Manual Manual for Software Version 1.0x
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General Sample Rate Conversion and Distribution

From ANY format: AES, SPDIF, Toslink, SDIF-2 at ANY sample rate:

11.025k, 12k, 16k, 22.05k, 24k, 32k, 44.1k, 48k, 88.2k or 96kS/s

Dual AES at 88.2k, 96k, 176.4k or 192kS/s

Quad AES at 176.4 or 192kS/s

DSD SDIF-2, DSD SDIF-3 or DSD Quad

or

or

or

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU REFERENCE LOOP SPDIF

IN OU T

AES CLK OUT SYNC INPUT

IN OUT

CH1 IN

RCA

BNC

TOS

WCLK IN

CH1 OUT

DSD / SDIF

LOOP IN

To ALL formats: AES, SPDIF, Toslink & SDIF-2 at ANY sample rate:

11.025k, 12k, 16k, 22.05k, 24k, 32k, 44.1k, 48k, 88.2k or 96kS/s
or

Dual AES at 88.2k, 96k, 176.4k or 192kS/s

or

Quad AES at 176.4 or 192kS/s

or

DSD SDIF-2, DSD SDIF-3 or DSD Quad

Figure 9 – General Sample Rate Conversion

The dCS 974 converts any one of 12 sample rates in any format to any of the 12
sample rates in ALL formats: 4 AES, 2 electrical SPDIF, optical SPDIF or
SDIF-2 outputs. Most frequency combinations (including all the primary ones)
are accommodated in one pass - see Table 2 on page 44. For best results,
slave the unit to the audio input, AES Ref Loop In or the SDIF-2 WCLK IN.

CH2 IN

LOOP OUT

CH2 OUT

WCLK OUT

REMOTE

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

do this: Connect any digital audio source of any word length between 8 and 24 bits,

using single AES or dual AES or quad AES to the AES inputs, or using single or
double speed SDIF-2 to the SDIF-2 inputs, or using single wire SPDIF to the
appropriate SPDIF input.

do this: Select Audio Input accordingly. Output via any of the outputs.

Sample Rate Conversion settings:

Sample Rate Conversion: On
Audio Input Select: Any, including Dual AES if the Input Sample

Rate is 88.2kS/s or more and Quad AES if the
Input Sample Rate is 176.4 kS/s

3

or 192kS/s.

Output Mode: Normal or Dual AES may be selected if the

Output Sample Rate is 88.2 kS/s or 96kS/s.

Dual AES or Quad AES must be used for

192 kS/s or 176.4 kS/s.

Other settings: Any.

3

It has to be Dual AES or Quad AES for 192 kS/s or 176.4 kS/s

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
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PCM to DSD

From PCM in ANY format: AES, SPDIF, Toslink or SDIF-2

at sample rates: 44.1k, 48k, 88.2k or 96kS/s

Dual AES at 88.2k, 96k, 176.4k or 192kS/s

Quad AES at 176.4 or 192kS/s

or

or

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

DSD Quad

AES / EBU REFERENCE LOOP SPDIF

IN OU T

AES CLK OUT SYNC INPUT

IN OUT

CH1 IN

RCA

BNC

TOS

WCLK IN

CH1 OUT

DSD / SDIF

LOOP IN

CH2 IN

LOOP OUT

CH2 OUT

WCLK OUT

REMOTE

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

DSD SDIF-2

or DSD SDIF-3

Figure 10 – PCM to DSD conversion

The dCS 974 converts PCM to DSD (including 176.4 kS/s to DSD) using the
arrangement given below:

do this: Connect any digital audio source of any wordlength between 8 and 24 bits,

using single, Dual or Quad AES to the AES inputs, or using single or double
speed SDIF-2 to the SDIF-2 inputs, or using single wire SPDIF to the
appropriate SPDIF input, and select the input accordingly.

do this: Set Output Mode to DSD SDIF-2 or DSD SDIF-3. Choose a Filter if you wish.
do this: Output SDIF-2 via the DSD/SDIF connectors, two data cables and one word

clock or SDIF-3 with just two data cables.

do this: Alternatively, take the DSD Quad output from the AES 1, 2, 3 and 4 outputs.

Sample Rate Conversion settings:

Sample Rate Conversion: On
Audio Input Select: Any, even including Dual AES or Quad AES at

higher Input Sample Rates

Sync Source:Any
Input Sample Rate:Any
Output Sample Rate:n/a
Output Mode: DSD
Filter:Any
Output Wordlength:n/a
Noise Shaping:n/a
Dither:n/a
Detect Silence:n/a

As an example, load Store H to take an input from AES1 and convert it to DSD
SDIF-2 or DSD Quad format.

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Using a Master Clock

DIGITAL OUT

16 bit / 44.1kS/s

digital audio

AES 1 AES 2 AES 3 AES 4

AES/EBU Outputs

[e-mail]

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

CH1(L) CH2(R) S ensitivity

Analogue

AES / EBU INPUTS

AES / EBU OUTPUTS

CH1(L) CH2(R)

LL R R

WORDCLOCK IN

L

Hand Crafted by

The Red Hot CD Player Co.

R

44.1kS/s

Wordclock

1 2 3 4 5 6

External

7 8 9 10 11 12

Wordclock Outp uts

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

Reference In Re ference Out AES1 AES2 AES3 AES4 CH 1 CH 2

PUSH PUSH PUSH PUSH PUSH

Digital I/O

IN OUT

RCA

BNC

TOS

Dual AES up to

24 bit / 192kS/s

DSD / SDIF

Sync

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

LOOP IN

WCLK OUT

SDIF-2/DSD

In Out

75R
Clk

Master Clock

REMOTE

dCS 992

Mains Fuse (2AT)

On Off

dCS 974

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

DDC

In

Loop

Remote

Out

dCS 954 24/192 DAC

In

Remote

Out

MAINS FUSE 2A(T) ON OFF

Balanced
Analogue

Outputs

do this: connect the Master Clock to the AES Ref Loop In and select AES Loop Term

do this: connect the Master Clock to the SDIF-2 WCLK IN and select Wordclock as the

IMPORTANT!

Unbalanced

Analogue

Outputs

Figure 11 – Using a Master Clock

If a Master Clock such as a dCS 992 is available and the driving source is locked
to it, the dCS 974 may be locked to it. Either:

as the Sync Source,

or:

Sync Source.

Since the Output Sample Rate of the dCS 974 is different to the Master Clock
rate, the DAC would be unable to lock to the data from the dCS 974 if it were
sync’ed to the Master Clock. So, slave the DAC to the dCS 974, NOT to the
Master Clock.

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dCS 974 User Manual Manual for Software Version 1.0x
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Converting Quad AES to CD Format

24 bit / 176.4kS/s Quad AES

from 8-track recorder

AES / EBU INPUTS

PUSH PUSH PUSH PU SH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

16 bit / 44.1kS/s

(CD format)

You can archive in 24 bit / 176.4kS/s or 192kS/s Quad AES format using a
standard 8-track digital recorder, then convert to other formats such as Red
Book CD.

Sample Rate Conversion settings:

Optional 44.1kS/s Wordclock

to 8-track recorder

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

IN OUT

RCA

BNC

TOS

DSD / SDIF

CH1 IN

WCLK IN

CH1 OUT

LOOP IN

CH2 IN

LOOP OUT

CH2 OUT

WCLK OUT

REMOTE

Figure 12 – Converting Quad AES to CD format

Sample Rate Conversion: On
Audio Input Select: Quad AES
Sync Source: Audio Input
Input Sample Rate: Auto
Output Sample Rate: 44.1kS/s
Output Mode: Normal
Filter:Any
Output Wordlength: 16
Noise Shaping: 9th Order
Dither: NS Triangular
Detect Silence: On

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

Provided the Output Sample Rate is set to one quarter of the Input Sample

Rate (i.e 176.4kS/s ⇒ 44.1kS/s or 192kS/s ⇒ 48kS/s), you can reduce jitter by

using the dCS 974 as the master clock and locking the recorder to it. Change

Sync Source to Internal, connect WCLK OUT (lower block) to the recorder’s

Wordclock input and set the recorder to slave.

Archive at 176.4kS/s for audio-based material, archive at 192kS/s for video­based material. Ensure the sample rates match the source material.

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Multi-channel Sample Rate Conversion – bit aligned sources

96kS/s

Ch1 & 2

96kS/s

Ch3 & 4

96kS/s

Ch5 & 6

96kS/s

Ch7 & 8

44.1kS/s

SOURCE

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

IN OUT

IN OUT

IN OUT

IN OUT

CH1 IN

CH2 IN

REMOTE

REMOTE

REMOTE

REMOTE

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

IN

LOOP

OUT

WCLK IN

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

Figure 13 – Multi-channel Sample Rate Conversion with bit aligned source

If the source data is bit aligned (for example, from a multitrack recorder) up to
four or five dCS 974’s may be set to operate synchronously using the sync link
connections shown above, from one unit’s AES CLK Out to the next unit’s AES

Ref Loop In. For all units, set the Multiple Channel Sync option to On. The

top unit will set up as a master, the other ones will set up as slaves. Make sure
that all the other settings are the same on each unit.

See the section Multiple Channel Sync’ing, page 81 for how aligned is bit
aligned.

These are set up, for PCM in to DSD out, in Store E, and for PCM in to 96kS/s
out in Store F.

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Multi-channel Sample Rate Conversion – Using a Master Clock

44.1kS/s

WORDCLOCK

TO RECORDER

44.1kS/s

SOURCE

AES 1 AES 2 AES 3 AES 4

AES/EBU Outputs

[e-mail]

A

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

1 2 3 4 5 6

7 8 9 10 11 12

Wordclock Outp uts

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

IN OUT

RCA

BNC

TOS

IN OUT

RCA

BNC

TOS

IN OUT

RCA

BNC

TOS

IN OUT

RCA

BNC

In

External

Loop

Sync

Out

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

Remote

dCS 992

REMOTE

Mains Fuse (2AT)

On Off

Master Clock

IN

LOOP

OUT

MAINS FUSE ( 2AT) ON OFF

96kS/s

Ch1 & 2

96kS/s

CH1 IN

CH2 IN

REMOTE

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

IN

LOOP

OUT

MAINS FUSE ( 2AT) ON OFF

Ch3 & 4

96kS/s

CH1 IN

CH2 IN

REMOTE

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

IN

LOOP

OUT

MAINS FUSE ( 2AT) ON OFF

Ch5 & 6

96kS/s

CH1 IN

CH2 IN

REMOTE

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

IN

LOOP

OUT

Ch7 & 8

Figure 14 – Multi-channel Sample Rate Conversion with Master Clock

You can use a dCS 992 Master Clock

4

to sync up the source and be the master.
The sync link cabling starts from the master clock (cable “A”) and then carries
on down units as shown. Use of the master clock allows more units to be used
together – 24 channels worth or more. For all dCS 974 units, set the Multiple

Channel Sync option to On. They will all set up as slaves. Make sure that all

the other settings are the same on each unit.

4

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Multi-channel Sample Rate Conversion – with more alignment tolerance

WORDCLOCKS

TO SOURCES

FROM

SOURCE

FROM

SOURCE

AES 1 AES 2 AES 3 AES 4

AES/EBU Outputs

[e-mail]

A

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

1 2 3 4 5 6

7 8 9 10 11 12

Wordclock Outp uts

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYN C INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYN C INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYN C INPUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYN C INPUT

C

IN OUT

RCA

BNC

TOS

IN OUT

RCA

BNC

TOS

IN OUT

RCA

BNC

TOS

IN OUT

RCA

BNC

dCS 992

In

External

Loop

Remote

Sync

Out

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SDIF

REMOTE

REMOTE

REMOTE

REMOTE

Master Clock

Mains Fuse (2AT)

On Off

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

IN

LOOP

OUT

MAINS FUSE (2AT) ON OFF

IN

LOOP

OUT

96kS/s

Ch1 & 2

96kS/s

Ch3 & 4

96kS/s

Ch5 & 6

96kS/s

Ch7 & 8

Figure 15 – Multi-channel Sample Rate Conversion with more alignment tolerance

A dCS 992 Master Clock

5

can also be used to sync the source and the dCS 974
units as above. In addition to the sync link cabling (starting with “A”), additional
clocking (cables “C”) allow the dCS 974‘s to extract clocks from the “C” cables
and extract the data from the signal input cables. The master clock outputs
different frequencies on the different cabling types. This allows considerable bit
alignment error, as might occur if some tracks are stored on one machine and
some on another. For all dCS 974 units, set the Sync Source to Wordclock and
the Multiple Channel Sync option to On. They will all set up as slaves. Make
sure that all the other settings are the same on each unit. Note that cable ‘A’
must NOT be driven from the dCS 992’s AES1 output.

5

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Multi-channel Sample Rate Conversion – with multiple sample rates out

A dCS 992 Master Clock6 can also be used to sync up the source and more
than one set of units, all at different sample rates, and be the master. DVD
production may require different sample rates for different channels – this set up
will give real time 48 kS/s rear channels and 96 kS/s front channels from a
multi-channel 44.1kS/s source. See Figure 16 overleaf. For all dCS 974 units,
set the Multiple Channel Sync option to On. They will all set up as slaves.
Make sure that all the other settings are the same on each unit in a group.

6

version 2.0 or higher software

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dCS Ltd May 2001

FROM

SOURCE

TO RECORDER

(44.1kS/s

WORDCLOCK)

FROM

SOURCE

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES 1 AES 2 AES 3 AES 4

AES/EBU Outputs

[e-mail]

A

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

1 2 3 4 5 6

7 8 9 10 11 12

Wordclock Outputs

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

AES CLK OUT SYNC INPUT

OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES / EBU REFERENCE LOOP SPDIF

IN OUT

IN OUT

IN OUT

IN OUT

IN OUT

IN OUT

IN OUT

IN OUT

BNC

TOS

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

TOS

RCA

BNC

CH1 OUT

CH2 OUT

DSD /

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

LOOP IN

WCLK OUT

External

Sync

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

LOOP IN

WCLK OUT

CH1 IN

CH2 IN

WCLK IN

LOOP OUT

CH1 OUT

CH2 OUT

DSD / SD IF

dCS 992

In

Loop

Remote

Out

REMOTE

REMOTE

REMOTE

REMOTE

REMOTE

REMOTE

REMOTE

MAINSFUSE (2AT) ON OFF

IN

LOOP
OUT

MAINSFUSE (2AT) ON OFF

IN

LOOP
OUT

MAINSFUSE (2AT) ON OFF

IN

LOOP
OUT

MAINSFUSE (2AT) ON OFF

Master Clock

Mains Fuse (2AT)

On Off

IN

LOOP
OUT

MAINSFUSE (2AT) ON OFF

IN

LOOP
OUT

MAINSFUSE (2AT) ON OFF

IN

LOOP
OUT

MAINSFUSE (2AT) ON OFF

IN

LOOP
OUT

48kS/s

Ch19 & 20

48kS/s

Ch17 & 18

48kS/s

Ch15 & 16

48kS/s

Ch13 & 14

96kS/s

Ch1 & 2

96kS/s

Ch3 & 4

96kS/s

Ch5 & 6

96kS/s

Ch7 & 8

Figure 16 – Multi-channel Sample Rate Conversion with multiple sample rates out

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x

Noi

g

dCS Ltd May 2001

HE SOFTWARE

T

TOP LEVEL Audio Input Select

Greyed out
menu entries
are not there
when Format

Conversion

is "On".

They prevent

bit for bit

operation.

Sample Rate

(SRC) / Format

ENU AND SETUPS

– M

Conversion

Conversion

(FC) menu

Sync Source

Multiple Channel Sync

Input Sample Rate

Output Sample Rate

DSD Clock

Output Mode

Filter

Output Word Length

Noise Shaping

Dither

AES Message Edit

AES 1

Audio Input AES 3

AES Loop AES 4

AES Loop Terminated Dual AES (1+2)

Wordclock Quad AES

Internal SPDIF1 (RCA)

Lab Ref (10MHz)

Off DSD SDIF-2 or -3
On DSD Quad

192 kS/s

176.4 kS/s
96 kS/s

88.2 kS/s
48 kS/s

44.1 kS/s
32 kS/s
24 kS/s

22.05 kS/s
16 kS/s
12 kS/s

11.025 kS/s

Filter 1
Filter 2

…

Filter n

Off …

1st Order 8 bits

…

10th Order

Professional On/Off

AES 2

SPDIF2 (BNC)

SPDIF3 (TOS)

PCM SDIF-2

192 kS/s

176.4 kS/s
96 kS/s

88.2 kS/s
50 kS/s
48 kS/s

44.1 kS/s
32 kS/s
24 kS/s

22.05 kS/s
16 kS/s
12 kS/s

11.025 kS/s
Auto

DSD/64 - 44.1kHz

DSD bit clock

Normal

Dual AES

Quad AES
DSD SDIF-2
DSD SDIF-3

24 bits
23 bits

Off

Top Hat

Triangular

se Shaped

ular

Trian

Not Indicated
Two Channel

Single Channel

Primary/Secondary

Stereophonic

Source Byte 1
Source Byte 2
Source Byte 3
Source Byte 4

Destination Byte 2
Destination Byte 3
Destination Byte 4

2-Ch Gen Format

Compact Disc

2-Ch Enc/Decode

DAT

Menu entries

in italics (and

the menus

below them)

may

disappear if

the selection

of other

parameters

makes them

unrealistic.

This mainly

happens with

DSD on.

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Non-Audio On/Off

Mode

Source

Destination

SPDIF Message Edit

continued …continued …

Page 34

Professional On/Off

Non-Audio On/Off

Copy Permit On/Off

Format

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dCS 974 User Manual Manual for Software Version 1.0x

g

q

y

dCS Ltd May 2001

…from "Top" …from "SRC"

Error Monitor

Gain/Balance

Swap Channels

Phase

Detect Silence

De/Pre-emphasis

Display Customise

CRC Errors Left

CRC Errors Right

Parity Errors Left

Gain adjust

Balance adjust

Reset max hold

Maximise

Normal

Swapped

On
Off

Off

De-emphasis 50/15 us +/- = add or remove

De-emphasis CCITT J17

Emphasis 50/15 us +/- Input

Emphasis CCITT J17 +/- Sync Source

Hold +/- L/R Flip

Reset +/- Filter Cut

Hold

Reset

Hold

Reset

Display max hold

Maximise!

Normal

Left inverted

Right inverted

Both inverted

+/- Output Mode
+/- Word Length

+/- Noise Shaping

+/- Dither

Test

Info

Bit Activity

Monitor

Level Meters

Display

Parity Errors Right

Invalid Errors Left

Invalid Errors Right

All Errors

Generator

Self Test

Decay

Peak Hold

htness

Bri

Contrast

uare

Off/Sine/S
Generator Amplitude
Generator Frequenc

Meter Type

Cursor Up / Down

Backlight off after

Hold

Reset

Hold

Reset

Hold

Reset

Hold

Unhold

Reset

Normal

Faster None

Fastest 320 ms

Instant 640 ms

Bar

Numerical

1 mins
3 mins
5 mins

960 ms
1280 ms
1600 ms

Infinite

Reset

Table 1 – Menu Tree

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Navigating through the Menu – what the On-Screen symbols mean

Once the unit has powered up and the Status screen is displayed, you can start
navigating through the menu. This section explains how the keys operate, and
what the various on-screen indications mean. To start, pressing either the ←←←← or

→→→→ button brings up the top level of the Menu:

The symbol is the cursor and an indication that there are sub-menus
available below this level. If there are no more submenus, it changes to
Turn the rotary control clockwise and the cursor will move down the list. Turn
the rotary control counter clockwise and the cursor will move back up. To
access the Sample Rate Conversion menu, set the cursor adjacent to

Sample Rate Conversion and press the →→→→ button. The screen will change to:

.

The cursor shape is still because the option selected has a lower level. The

symbol in the lower right hand corner indicates that there are more options
available than can be displayed. Use the rotary control to move the cursor down
the list. When the cursor reaches the bottom of the screen, the list will scroll
upwards and a
are more options above. When the bottom of the list is reached, the

appear in the upper right hand corner to indicate that there

symbol

disappears.

The screen displays:

Move the cursor back up to Balance/Gain and press the →→→→ button to display
the bottom level:

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dCS Ltd May 2001

The cursor has changed to to indicate that the bottom level has been
reached. Turning the rotary control will move the cursor up and down the list.

Now press the Set button to accept Gain and the cursor changes to

to
indicate that this parameter (Gain) may now be adjusted using the rotary
control. Turn the control either way and the Gain changes in 0.1dB steps. When
the required setting is reached, press Set and the cursor will change back to

.

Pressing ←←←← when the cursor is

Pressing Set when the cursor is

or returns to the previous menu level.

and the option cannot be adjusted (e.g.

AES 1 in the Audio Input Select menu) selects that option and returns to the

previous menu level.

From the Status screen, pressing any of the four Operation buttons displays
the last menu level used.

Pressing the Status button when the cursor is

or displays the Status

screen for the selected menu.

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dCS 974 User Manual Manual for Software Version 1.0x
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Top Menu

The top menu contains the major entries: - Sample Rate Conversion, Format

Conversion, Error Monitoring, Test, Info, Bit Activity Monitors, Level Meters

and Display – as follows:

In many cases, the settings in one menu do not affect those in others. In other
cases they do, and where this occurs the menu will automatically adjust to allow
only valid options.

The unit can operate in one of two main modes – Sample Rate Converter
(SRC) mode and Format Converter (FC) mode. In SRC mode, the unit

performs DSP on the signal and gain is always reduced by 0.01dB. This is
because many of the other operations, such as dithering or noise shaping, add
a small amplitude signal, so we reduce the amplitude a small amount to prevent
spurious clips.

It also means that for simple operations such as Dual AES in to double speed
AES out, bits in will not be the same as bits out. Because in some cases this is
important, the unit can also operate in FC mode. FC mode has no (0dB) signal
drop, and will not allow operations that can cause audio data bit changes – but
it does allow bit for bit copies of signals to be made in different digital formats. It
also allows message editing, but many of the other options available in SRC
mode are removed from the menus while FC mode is active.

SRC mode offers all the options of FC mode – FC mode just turns off the

options that affect bit for bit performance. There are no options that are just
available in FC mode.

Sample Rate Conversion

The default setting is Sample Rate Conversion (SRC) mode on, Format

Conversion (FC) mode Off. Pressing →→→→ will open the Sample Rate
Conversion menu.

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Format Conversion

The default setting is SRC mode on, FC mode Off. To turn FC mode on, select

Format Conversion and press →→→→. The menu below will appear:

Pressing Set will toggle the state from Off to On. The unit will check to see if
the Output Sample Rate is the same as the Input Sample Rate, and if it is
not it asks you to press Set to change the Output Sample Rate, or any other
button to cancel the attempt to turn FC mode on.

Error Monitoring

Test

Info

On returning to the main menu, Sample Rate Conversion is shown as
disabled:

To re-enter SRC mode, you have to set Pure Format Conversion to Off.

Error monitoring on the input signal can be implemented for CRC, Parity and
Valid bits in the AES3 and SPDIF message streams. This menu covers
resetting the monitors, and is only available for PCM inputs – the entry
disappears for DSD inputs.

The unit can be used as a very high purity signal generator, as well as
performing self test functions, via this menu.

This menu displays information about the unit, for support purposes

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Bit Activity Monitors

This menu turns on bit activity monitors on the selected input signal, for use on
the audio data – it can find out how many active bits you have coming in, or
identify stuck bits in other equipment. This only works for PCM inputs – the
entry disappears for DSD inputs. This feature does NOT monitor the units
outputs.

Level Meters

Controls level metering of the output data. The level meters may be used to
monitor DSD signals by setting a DSD to PCM conversion. Even though the
conversion may not be used, the level metering will effectively meter the DSD
input.

Display

Controls the Brightness, Contrast, Cursor direction and Backlight timeout
behaviour of the display.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Sample Rate Conversion / Format Conversion Submenu

The Sample Rate Conversion menu is as follows:

Audio Input Select

Select the required input from the list and press Set. The Dual AES option
requires that the Input Sample Rate be set to 192 kS/s, 176.4 kS/s, 96 kS/s or

88.2 kS/s. The Quad AES option requires that the Input Sample Rate be set to
192 kS/s or 176.4 kS/s. The DSD setting automatically identifies DSD SDIF-2 or

DSD SDIF-3 data on the DSD/SDIF input.

Sync Source

Select a source to synchronise to from the list and press Set. The available
sync sources are:

Audio Input Syncs to the selected input source – this is the

normal setting.

AES Loop Syncs to the AES Ref Loop In, leaving the

reference unterminated to allow daisy-chain
connection through Loop Out to another device.

AES Loop Term Syncs to the AES Ref Loop In and terminates the

reference source.

Wordclock Syncs to DSD/SDIF WCLK IN (in the upper group

of connectors).

Internal Syncs to the dCS 974’s internal clock.
Lab Ref Syncs to a 10 MHz signal into DSD/SDIF CLK IN

(in the upper group of connectors).

For best results, synchronise to the Audio Input or a master clock on one of
the clock/reference inputs that is also driving the source. For DSD/SDIF inputs,
you can still sync to Audio Input as the unit will automatically sync to

DSD/SDIF WCLK IN. For DSD in SDIF-2 or SDIF-3 mode, a Wordclock must

be used – contact dCS if you need a Bit Clock.

The Lab Ref setting allows use of a GPS reference - if you use this, make sure
other parts of your system are also GPS sync’d.

Only select Internal sync if you are using the unit as a signal generator or a
reference clock source.

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Multiple Channel Sync

This option is either On or Off.

The unit uses the AES Ref Loop In as a sync link. When On, if the unit detects
a sync signal into the AES Ref Loop In, it will sync to it and set up as a Slave.
If there is no sync signal coming into the AES Ref Loop In, it will set up as a
Master. See section Multiple Channel Sync’ing, page 81 for an explanation, or
the multi-channel applications from page 29 for wiring. Do not feed a signal with
active User bits into AES Ref Loop In with Multiple Channel Sync turned on!

When the option is On, the Status display informs you about the unit’s
configuration. If an active signal is connected to the AES Ref Loop In, but it
does not carry User bits, the unit thinks it is a Single unit, and the Status
display is as follows:

If no signal is connected into the AES Ref Loop In (there is no sync link going
in), the unit thinks it is a Master and the Status display is as follows:

If the sync link is connected and active, the unit thinks it is a Slave, and the

Status display shows:

For multi channel syncing on DSD to DSD, the sync link does not synchronise
all the output Wordclocks. Each unit will have a different phase. Just use the

Wordclock from one unit and ignore the rest – the group delays for the signals

will not be affected.

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Input Sample Rate

For PCM input modes, the input sample rate can be sensed and set
automatically, using the Auto option, or forced. The latter is useful where use of
1 or 2 wire mode for higher sample rates might be ambiguous – otherwise Auto
is best. It occurs at the bottom of the Input Sample Rate list:

Select the required entry from the list and press Set. If you have selected Auto,
then the list changes when re-entered:

Output Sample Rate

and the Status display will indicate that Auto is on:

Output Sample Rate is a parameter for PCM output modes only. Select the

required Output Sample Rate from the list and press Set. The dCS 974
accepts 112 input / output sample rate combinations (including DSD) in one
pass. The remaining 70 combinations can be accommodated in 2 passes.
These are shown in Table 2 overleaf.

Not all the apparently valid output sample rates may be available to you from
the menu. When Auto Input Sample Rate Selection is turned on, the menu
system dynamically alters the Output Sample Rate menu to reflect the valid
1 pass output rates for the current input rate. For example, if Auto is turned on
and the input is running at 96 kS/s, then the Output Sample Rate menu would
look like this:

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OUTPUT SAMPLE RATE (kS/s)

11.025 12 16 22.05 24 32 44.1 48 88.2 96 176.4 192 DSD

)

INPUT SAMPLE RATE (kS/s

11.025

22.05

176.4

1 pass 1 pass 2 pass 1 pass 1 pass 2 pass 1 pass 2 pass 1 pass 2 pass 2 pass 2 pass 2 pass

12

1 pass 1 pass 2 pass 1 pass 1 pass 2 pass 2 pass 1 pass 2 pass 1 pass 2 pass 2 pass 2 pass

16

2 pass 2 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 2 pass 1 pass 2 pass 2 pass 2 pass

1 pass 1 pass 1 pass 1 pass 1 pass 2 pass 1 pass 1 pass 1 pass 2 pass 2 pass 2 pass 2 pass

24

1 pass 1 pass 1 pass 1 pass 1 pass 2 pass 1 pass 1 pass 2 pass 1 pass 2 pass 2 pass 2 pass

32

2 pass 2 pass 1 pass 2 pass 2 pass 1 pass 1 pass 1 pass 1 pass 1 pass 2 pass 2 pass 2 pass

44.1

1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass

48

1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass

50

2 pass 2 pass 2 pass 2 pass 2 pass 2 pass 1 pass 1 pass 2 pass 2 pass 2 pass 2 pass 1 pass

88.2

1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass

96

1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 2 pass 1 pass 1 pass

2 pass 2 pass 2 pass 2 pass 2 pass 2 pass 1 pass 2 pass 1 pass 2 pass 1 pass 2 pass 1 pass

192

2 pass 2 pass 2 pass 2 pass 2 pass 2 pass 1 pass 1 pass 1 pass 1 pass 2 pass 1 pass 1 pass

DSD

2 pass 2 pass 2 pass 2 pass 2 pass 2 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass 1 pass

Table 2 – One Pass and Two Pass Conversions

If the input sample rate were 32 kS/s, then the display would offer a different
selection:

The input sample rate can be changed to one that is incompatible with the
currently selected Output Sample Rate, because it needs a 2 pass operation.
As an example, we might have 11.025 kS/s coming in (not on Auto), and try to
select 96 kS/s. The dCS 974 will detect that this ought to be a 2 pass operation
and display the following information box:

While displaying this information box, the output of the dCS 974 will be muted.
To continue, either:

do this: Change the Input Sample Rate to one suitable for conversion (see the table

above) or

do this: Press any key, and the dCS 974 will display a list of valid Output Sample

Rates, as follows (for our 11.025 kS/s example):

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dCS 974 User Manual Manual for Software Version 1.0x
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For a 2 Pass conversion, convert the input to an intermediate sample rate and
either feed it direct into another dCS 974 or record the result, then convert from
the intermediate sample rate to the required sample rate. You can always
choose one of 44.1 kS/s or 48 kS/s as the intermediate sample rate, so you can
record the intermediate pass on most recording devices.

However, it is best to use the highest possible sample rate for the intermediate
pass, if your recording device can take it. For example, to convert from 192 kS/s
to 12 kS/s, first convert from 192 kS/s to 96 kS/s, and then convert from
96 kS/s to 12 kS/s. Use of two dCS 974’s avoids intermediate storage.

Output Mode

For DSD output, select DSD SDIF-2 or DSD SDIF-3, and the unit will make the
appropriate changes. The unit supports DSD out with either DSD or PCM in.
DSD output includes a DSD DC blocking filter. All signals in DSD or PCM will
have their DC filtered out. When set to either DSD output mode, a DSD Quad
signal appears on four output cables – AES 1, AES 2, AES 3 and AES 4. The 3
SPDIF outputs all carry identical AES streams with no data – they may be used
for synchronisation.

Filter

For PCM output, select Dual AES to output a 192kS/s, 176.4kS/s, 96 kS/s or

88.2 kS/s AES3 signal on two output cables – AES 1 and AES 2 (or AES 3 and

AES 4). In this mode, the AES Clk Output and 3 SPDIF outputs all carry

identical AES streams with no data – they may be used for synchronisation. The

SDIF Clk Output sends Wordclock at the same rate as on AES 1, do not use

the SDIF data outputs while in Dual AES mode.

For PCM output, select Quad AES to output a 192kS/s or 176.4kS/s AES3
signal on four output cables – AES 1, AES 2, AES 3 and AES 4. In this mode,
the AES Clk Output and 3 SPDIF outputs all carry identical AES streams with
no data – they may be used for synchronisation. The SDIF Clk Output sends
Wordclock at the same rate as on AES 1, do not use the SDIF data outputs

while in Quad AES mode.

Otherwise, set to Normal for single wire outputs on AES 1, AES 2, AES 3 &

AES 4, the three SPDIF outputs and the SDIF-2 output.

For PCM out, the unit can have PCM or DSD in.

The dCS 974 offers a choice of filter for use on some of the more popular in/out
combinations. The filters offer differing responses. For PCM outputs, Filter 1 in
each case offers the sharpest cut-off and no or least aliasing, but longest
energy smear. Filter 4 gives the gentlest roll-off (usually with significant aliasing)
but the shortest transient response with least smear. For DSD output, the
differences are not so great – the responses are given in the section dCS 974

Performance Curves, page 94. The conversions that offer multiple filters are

as follows:

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

In Out Number of Filters Available

DSD DSD 8

PCM DSD 8

192 96 4

176.4 88.2 4

176.4 44.1 4
96 48 4
96 44.1 4

88.2 44.1 4
48 44.1 4

44.1 96 4

Table 3 – Conversions with Multiple Filter Options

We encourage you to experiment with the filters, to find the one that sounds
best for your particular application. Do not assume that one filter is best for all
applications!

7

The menu is dynamic - that is, it updates to show valid selections. For example,
Fs In = 96kHz, Fs Out = 44.1kHz has 4 options and shows:

While Fs In = 96kHz, Fs Out = 88.2kHz has only one option and shows:

The dCS 974 remembers the last filter selection for every conversion, so if you
choose Filter 4 for 96Ö44.1 and Filter 2 for 96Ö48, these separate settings will

be stored and loaded when you switch between them.

Output Word Length

Select the required Word Length from the list and press Set.

IMPORTANT!

The dCS 974 generates long word length (24 bit) data and truncating this
adds extra noise. It can also add highly undesirable behaviour at low signal
levels. We recommend that you use a high order noise shaping function, but
see the section Word Length Reduction, page 104 and try for yourself.
This is a seriously major topic, and you should experiment.

7

The reports we receive from users suggest that for PCM work, Filter 2 is well suited to some classical music,

and that Filters 3 and sometimes 4 suit rock. However, views vary quite a lot.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Noise Shaping

Noise Shaping is a technique in which the noise energy added by truncating a
longer word is pushed into the less audible parts of the spectrum - giving a
useful improvement in perceived noise level. There is a trade-off between noise
floor improvements in the mid-band, where the ear is most sensitive, and
increased noise at the top of the audio band, which the ear does not hear but
your system might. Noise Shaping is achieved by processing the truncated bits
so it is not available if the output word length is the same as the input word
length. Dither is different (and additional) to Noise Shaping, and is necessary
under some circumstances. dCS consider Dither to be unnecessary in many
situations - Noise Shaping alone is sufficient, and lower noise. See the section

Word Length Reduction, page 104 for more information.

Entering the menu shows:

Dither

Select the required Noise Shaping characteristic from the list and press Set.
The options are up to 10
is not applicable to DSD. For 32 kS/s, 44.1 kS/s, 48 kS/s, 88.2 kS/s and 96 kS/s
the curves are individually optimised

th

order, for sample rates up to 96kS/s. Noise Shaping

8

.

Entering the Dither submenu shows:

Select the required Dither characteristic from the list and press Set.

N. Shaped Triangular means Noise Shaped Triangular.

For more information on dither, and different dither types, see the section

Dither on page 85 and Figure 31 to Figure 34.

8

If you need curves optimised at other sample rates, contact us.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

AES Message Edit

This menu sets the message bits on the AES outputs.

Professional On/Off Select then press Set to toggle between On

and Off.

Non-Audio On/Off Select then press Set to toggle between On

and Off.

Mode Select the audio data format then press Set.

Options are:

Not indicated
Two channel
Primary/Secondary
Stereophonic

Source Select each of the four bytes in turn, press Set,

turn the rotary control to change the character
as necessary and press Set again to accept.

Press ←←←← to return to the previous menu and the
four characters will be displayed beside
“Source”.

Destination Set up similarly to Source.

SPDIF Message Edit

This menu sets the message bits on the SPDIF outputs.

Professional On/Off Select then press Set to toggle between On

Non-Audio On/Off Select then press Set to toggle between On

Copy Permit On/Off Select then press Set to toggle between On

Format Select the audio data format then press Set.

Gain/Balance and Maximise

This menu allows gain (output level) and balance to be set, or an automatic gain
setting to get the highest possible level without overload – for CD preparation,
for example. The balance control works in a different way to conventional
(analogue) balance controls, and although is easy to operate, you should be
aware of what it does.

To set the gain, select Gain then press Set. Turn the rotary control to adjust the
Gain anywhere between –100.0 dB and +12.0 dB in 0.1 dB steps
again to exit.

and Off.

and Off.

and Off.

Options are:

2 Channel General Format
Compact Disk
2 Channel Encode/Decode
DAT

9

. Press Set

9

The

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-0.01 dB. This is because noise shaping, dither, and a few other mechanisms can add (small) amounts to an
input signal, but enough to cause digital clipping. The -0.01 dB global gain shift avoids the problem.

dCS

has a global gain of -0.01 dB absolute, so when the unit says “0 dB” the overall gain will be

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

IMPORTANT!

do this: At the start of the track, select Maximise then Reset max hold and press Set.
do this: At the end of the track, select Maximise then Maximise! and press Set. The

do this: Replay the track and the gain will be Maximised.

Use positive gain with care as the unit does not monitor overloads. If in
doubt, use Maximise instead.

With Balance set central (i.e. L 0dB, R 0dB), no gain is applied to either
channel. Panning to the right attenuates the left but does not amplify the right
channel and vice versa. This arrangement helps avoid overloads.

To set the balance, select Balance then press Set. Turn the rotary control to
adjust the balance anywhere between 0.0 and -6.0dB on either channel in

0.2dB steps. Adjustment beyond -6.0dB mutes that channel. Press Set again to
exit.

Maximise is a feature that makes best use of the available dynamic range. The

dCS 974 keeps a running record of the maximum amplitude of the signal.
Maximise can then apply the exact gain to ensure the highest signal peak noted
is boosted to full scale.

The maximum gain that may be applied is +12dB. If the correction exceeds this,
+12.0dB of gain will be applied. Please note that Maximise cannot correct
overloads. Maximise can be run repeatedly if you have a lot of gain to max up.

gain correction will be applied.

Swap Channels

Phase

Select Maximise then Display max hold and press Set to see the current
peak signal record.

This allows the left and right channels to be swapped. For normal operation,
select Normal and press Set. To swap channels, select Swapped and press

Set - the L/R Flip LED will light up.

The options for Phase are:

Normal Select then press Set. Outputs are in phase with

inputs. Both Phase indicators are off.

Left Inverted Select then press Set. Left channel is out of phase

with input, Right is in phase. Left Phase indicator
lights.

Right Inverted Select then press Set. Right channel is out of

phase with input, Left is in phase. Right Phase
indicator lights.

Both Inverted Select then press Set. Both channel outputs are

out of phase with inputs. Both Phase indicators
light.

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dCS 974 User Manual Manual for Software Version 1.0x
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Detect Silence

Detect Silence is a PCM only option that gives digital silence out if the unit

detects digital silence in. This is useful where dither, and/or noise shaped
truncation are being used – without it, even if the signal in goes to digital
silence, the output will continue to output low level noise. It allows some
automation further along the CD preparation chain. The options are:

On Select then press Set. Output goes silent after

about 25 ms of silence in. Output recovers
immediately when the input goes live, although it
takes about 25 ms for the dither to turn back on if
this is used.

Off Select then press Set

IMPORTANT!

De/Pre-Emphasis

IMPORTANT!

Display Customise

Digital Silence detection does not currently operate in DSD modes.

For Output Sample Rates of 32kS/s to 96kS/s, Emphasis may be applied or
removed using this menu. The menu displays:

Select the appropriate function, and press Set.

Note that the unit drops the signal level by 12dB when applying pre­emphasis, to prevent overloads occurring.

When removing pre-emphasis (de-emphasising) there is no signal drop. When
units are run back to back, therefore – in any order – applying and removing
pre-emphasis, there will always be a 12 dB signal drop.

This menu allows the user to determine which five parameters are displayed on
the status screen in addition to input and output sample rates. The active

parameters in the list are indicated by the

x

sign in the box next to it. For

example:

indicates that the five displayed parameters are Input, Sync, O/P Mode,

W Length and N Shape. Dither and the options further down the list are not

displayed.

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To display a parameter that is not marked, first check that no more than four
parameters in the list are marked. If so, select the extra parameter and press

Set - an

x

sign will appear in the box next to it.

If five parameters are already marked, select an unwanted one and press Set;
the x

sign will disappear. Then select the wanted parameter and press Set.

The parameters available are:

Input Audio input selection
Sync Synchronisation source
O/P Mode Output mode
W Length Word Length
N Shape Noise Shaping characteristic applied
Dither Displays Dither type used
L/R Flip
Filter Displays Filter Cut used

With the top five parameters selected, the Status screen might look like this:

With the bottom four parameters selected, the Status screen might look like
this:

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dCS 974 User Manual Manual for Software Version 1.0x
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Error Monitor Submenu

The dCS 974 keeps count of CRC, Parity and Invalid errors and displays them
on the Error Monitoring screen. To view this, go to the top level menu, select

Error Monitor and press Status:

This shows the error count on Left and Right channels separately since the last
reset.

Error Hold and Reset

Select the Error Monitor menu and press →→→→ to display the next level menu:

Press →→→→ again to display the options for CRC Error Left:

Select either Hold or Reset and press Set. The screen display changes to the
Error Monitoring status. Hold stops the count for that error type and Reset sets
the count to zero. Each error count may be stopped or reset in this way. The All

menu applies the changes to All Errors.

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dCS 974 User Manual Manual for Software Version 1.0x
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Test Submenu

Generator Overview

The dCS 974 includes a high quality digital signal test generator, with both sine
or square wave outputs, and displays its settings on the Test Mode screen.
When invoked, the generator adjusts its output format to that currently
operating, and substitutes the generated output for any input signal. The
generator operates at the output sample rate. In PCM modes, it is a PCM
generator (in the appropriate mode), in DSD mode it is a DSD generator

If the unit is sync’d to an input when it goes into Generator mode, then the
generator stays sync’d to that input (so the output will be synchronous and
locked).

10

.

IMPORTANT!

If the unit is not sync’d to anything, set the Sync Source to Internal.
Otherwise, the equipment you are trying to drive may be unable to lock to the
Generator outputs because the sample rate has drifted out of lock range.

The Sample Rate Conversion menu is still active in Generator mode, so it can
enter Generator mode with no external syncing, the Generator can be set up, a
sync input can be selected from the Sample Rate Conversion menu and the
unit will sync to that. Noise shaping and other features available in the Sample

Rate Conversion menu can still be used, as long as these operate at the

output rate. Filters, for example, do not affect the generator output, because
they operate on the input signal. Dither operates at the output rate, so it can be
used.

Controlling the Generator

To view the Test Mode screen, go to the top level menu, select Test and press

Status to get the display below (assumes 96kS/s sync source):

If the unit is set to Internal sync, the screen will show Int beside the input
sample rate as follows:

10

in DSD mode it is a PCM generator, operating at a sample rate of 705.6 kS/s, and then converted to DSD.

This means that the maximum frequency that it can produce is 352.8 kHz.

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dCS 974 User Manual Manual for Software Version 1.0x
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To set up the generator, press →→→→ twice to move to the menu screen then
display the Test menu:

The Generator options are Off, Sine and Square. Press Set slowly to scroll
through these. There is a short delay while the generator code is loaded.

IMPORTANT!

The initial Generator Amplitude is -18dB0. If the dCS 974 is ultimately
driving speakers or headphones, ensure the system gain is at a reasonable
level before turning the generator on.

Generator Amplitude Adjustment

Select Generator Amplitude and press Set to adjust it. Turn the rotary control
counter-clockwise to reduce the amplitude in 0.5dB steps or clockwise to
increase it. Attempting to increase the amplitude above 0dB causes the setting
to wrap around to -120dB. When the required amplitude is displayed, press Set
again to update the setting.

Generator Frequency Adjustment

Select Generator Frequency and press Set to adjust it. The following screen
appears:

The frequency resolution of the generator is about 1 part in 231 of the sample
rate – about 10µHz at 48 kS/s. Rotating the knob moves the arrows left and

right. When the arrows point to the digit that you want to edit, press the Set
button. The knob will now increment or decrement the selected digit. If you
increment the digit beyond 9, then the next digit gets incremented, and the
current digit is set to 0. Similarly if the digit is at 0, decrementing it will change
the previous digit(s). For example, the above display shows 1kHz. If we
decrement the .0001 digit, the result is as follows:

When you have set the frequency you want, move the arrows to the ```` symbol
and press Set. To discard the changes and return to the tone generator menu,

move the arrows to the

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x

symbol and press Set.

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

IMPORTANT!

Self Test

If you select a frequency that is more than

automatically be set to

outputFs

.

2

outputFs

2

, the frequency generator will

Select Generator: Off and press Set - it will toggle to Generator: Sine. Wait
several seconds for the code to load up, then press again and it will change to

Generator: Square. Press again and it will return to Generator: Off. Press

Status to display the Test Mode screen:

The label appears on all status screens while the generator is on.

With the Generator On, the signal path from the selected input is disabled
and replaced by the Test Generator signal.

The Generator is turned off and reset to -18.0dB, 1kHz at power down.

The last option on the test menu is Self Test - this exercises the LEDs and the
LCD display. Select this and press Set. If all is well, the LEDs will flash in
sequence and the LCD will display a pattern of flashing columns. Press any
button to exit from this.

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dCS 974 User Manual Manual for Software Version 1.0x
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Info Submenu

To display information about the unit, return to the top level menu, select Info
and press Set. The Info screen will be displayed:

The first three lines give important details about the hardware and software
installed in your dCS 974. This is helpful if you experience difficulties with your
unit. Line four is dCS E-mail address for use if you need any further assistance.
The last two lines give you a hint of the options available on your machine.

Bit Activity Monitor Submenu

Bit Activity Monitoring Overview

This monitors activity on the selected input and indicates the wordlength of the
data provided by the source device. Because the monitor works on the input, it
can be used for DSD outputs if the input is PCM. To monitor the PCM output,
use Level Meters instead.

Setting the Monitor

To access the monitor, return to the top level menu, select Bit Activity Monitor
and press Set or Status. With a substantial 20 bit input signal, the display will
be similar to this:

The display is updated approximately three times per second.

The Display Timeout function is disabled while the Bit Activity Monitor is
being used.

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Level Meters Submenu

Level Meter Overview

The Level Meters monitor the Left and Right output signal levels. They work
on all PCM signals, and can be used to monitor DSDby setting a DSD to PCM
conversion.

The dCS 974 can be used purely as a programmable meter. Because the meters
work on the output data, the filters can be used to change the bandwidth of the
meters. For example, they can be used to monitor 96kS/s data with a 20kHz
bandwidth, by setting the output rate to 44.1kS/s, or the full bandwidth can be
examined by setting the output rate to 96kS/s.

The Display Timeout function is disabled while the Level Meters are being
used.

Turning the Level Meters On

To access the Meters, return to the top level menu, select Level Meters and
press Set or Status. With an input signal applied, the display will look similar to
this:

The bar consists of 27 segments, each representing 1dB. The dashed
segments at the right end of each bar are the Peak Hold indicators.

The indicator on the lower of the two bars shows that overloads
signals) have occurred in the last monitoring period, on that channel (it says
“Over” if you peer closely). The decay of the overload is controlled by the Peak

Hold function in the Level Meters menu (below).

Numerical metering to a resolution of 0.1dB can be set up instead, for example
for accurate alignment in comparisons. See Meter Type below to do this – the

display will change to:

11

because the

Format Conversion mode and the input signal goes to full scale.

dCS 974

reduces the signal level by 0.01dB, this can only occur if gain is applied, or if the unit is in

11

(full scale

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Meter Type (Bar or Numerical)

To change between Numerical or Bar level metering, or to change the meter
characteristics, return to the Level Meters menu and press →→→→ to display the
options:

Decay Time

Select Decay and press Set to display the Decay time options:

Peak Hold

These options give the following characteristics:

Normal the bar length decays away at 32 ms/segment
Faster the bar length decays away at 16 ms/segment
Fastest the bar length decays away at 11 ms/segment.
Instant the bar length decays away completely in 32ms.

Select the required Decay Time and press Set.

Select Peak Hold and press Set to display the Peak Hold options:

Scroll down to see the bottom of the list of options:

The unit notes the highest signal peak on each channel and turns on the
appropriate meter segment on each bar. The Peak Hold segment remains for
the set time and is then replaced by the next signal peak.

The menu options function as follows:

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None Disables the Peak Hold feature.
320ms thru 1600ms Sets the Peak Hold time.
Infinite Sets an infinite Peak Hold time.
Reset Resets the Peak Hold segments to the current

peak.

Select the required option and press Set. Infinite allows the highest peaks in a
track or long passage to be displayed – you might want this to do a manual
maximise:

do this: Select Infinite and press Set.
do this: At the start of the track, select Reset and press Set.
do this: Press Status to display the meter.
do this: At the end of the track the highest peaks will be displayed.
do this: Select Reset again and press Set to clear the peak readings.

Using the dCS 974 to monitor a track

If you just want to use the dCS 974 as a level monitoring device, you can control
the bandwidth you monitor by setting the output data rate – 44.1kS/s will give
approximately 20kHz bandwidth, whereas 96kS/s will give approximately 40
kHz bandwidth.

The meters can be used to monitor DSD by setting a DSD to PCM conversion,
and using the appropriate output data rate.

Watch Out for this One!

If the unit is tested with sine waves at frequencies which divide almost exactly
into the sample rate (e.g. 6.001kHz signal, 48 kS/s sampling frequency), the
segments on the right hand side of the meter will flicker. This effect disappears
if the signal frequency is changed by about 10Hz and so it is not a problem
when monitoring music. It is caused by the signal beating with the sample rate.

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Display Submenu

The final option on the top level menu is Display. Select this and press →→→→ :

Bright adjusts the brightness of the display backlight and Contrast adjusts the

LCD display contrast. These should be set for optimum readability. The length
of the solid bars indicate the setting of each parameter - there are 27 levels for
each.

To adjust the brightness, select Bright and press Set. The cursor will change to
the

symbol. Set the required brightness with the rotary control then press Set

again to exit adjustment mode. The Contrast is adjusted in a similar manner.

OOPS!

It is possible to turn the contrast to such a low setting that it is very difficult
to read the display. If this happens and the menu level is changed, you may
not be able to see the display well enough to navigate to the Display menu
and increase the contrast to readable level. To recover from this you can
Recall a stored setup known to have a higher contrast setting (see the next
section). If the worst happens and none are available, switch off the unit then
hold down the Status button while switching on. The unit will display

Using Default Settings and will load a setup with high contrast.

The third option (Cursor) controls the way the cursor responds to turning the
encoder. The default setting is the cursor moves down if the encoder is turned
clockwise. If you prefer the opposite arrangement, move the cursor to the
bottom line and press Set. “Clockwise = Down” changes to “Clockwise = Up”.
Pressing Set again change back.

The fourth option determines the time after which the display backlight goes out.
The backlight is an electroluminescent device, and so in theory has limited life.
It can also buzz a little, and although we select for low buzz, and acoustically
damp it, it can be irritating. So – the display goes dark after a preset period,
although pressing any button or turning the knob will wake it up again. When
the cursor is against the Backlight Off After option, each time you press Set it
steps through the settings 1 min, 3 min and 5 min.

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Setups and Locking the Front Panel

Storing a Setup

The dCS 974 features 12 non-volatile user programmable setup stores, labelled

Store 0 to Store 11. These are accessed by the rotary control and the block of

four MEMORY buttons on the lower left hand corner of the unit.

First set up the unit as required then press the Store button. If nothing has been
stored yet, the display will look like this:

You can scroll up and down the list using the rotary encoder and reveal the
other five stores. Scroll to the required store (e.g. Store 4) and press the Edit
button. The display changes to:

To edit the first character in the name, press the Edit button again. The display
changes - an alphanumeric screen is displayed, with the current store name at
the top, and all of the legal characters below it, as follows:

Turn the knob to move the edit block

E backwards and forwards through the

available characters. The arrow ↑↑↑↑ indicates which character you are editing, and
the character is updated in real time as you move the edit cursor.

The

↵↵↵↵

symbol represents <End>. When you have finished editing the

character, press the Edit button to return to the previous screen and select the
next character to edit. Names can be up to 15 characters long, plus an <End>
character to mark the end of the name. If all 15 characters are used and you
attempt to edit the <End> character in the 16th slot, the Edit button has no
effect. Inserting <End> half way through a name will complete the name there,
deleting the right hand portion.

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If Store 4 has been named Demo, the display will now look similar to this:

Press the Enter button and a message window will appear in the display to
confirm that the unit is storing the setup.

If you attempt to store a setup in a previously unused location without specifying
a name, a message window appears for two seconds, stating “First choose a

name!”.

You can name your stored setups as anything you like provided the name is no
longer than 15 characters. If you have a fixed routine, a few words may be
enough to describe the setup. If the unit is used for many different functions by
several people, we suggest using the following abbreviations to describe the
setup.

Audio Input use AES1, AES2, RCA, etc, DA for Dual AES, QA

for Quad AES, DSD for DSD SDIF, DSDQ for DSD

Quad.
Input Rate use Au for Auto, 44 for 44.1kS/s, etc.
Sync source leave blank if synced to Audio Input or use AR for

AES Reference, MC for Multiple Channel Sync,

WC for Wordclock or Int for Internal.

Output Rate use 44 for 44.1kS/s, or 2496 for 24 bits 96kS/s, or

CD for 16 bits 44.1kS/s.

Output Mode leave blank for Normal, DA for Dual AES, QA for

Quad AES, DSD2 for DSD SDIF-2 or DSD3 for

DSD SDIF3.

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Fixed Setups

In addition to the 12 user setups, there are 12 fixed setups which cannot be
changed. These are contained in the software and may be added to in future
software updates.

Store A AES1 Au>24 44

Contains default settings: Auto input on AES1,

sync to Audio Input, 24 bits 44.1kS/s output in

Normal mode. If you get the unit into a tangle,

recall this and sort things out.

Store B DA Au>CD N9 F2

Auto Dual AES input to CD format, 9th order

Noise Shaping, Filter 2, Detect silence On, Gain

set to -0.1dB.

Store C QA Au>CD N9 F2

Auto Quad AES input to CD format, 9th order

Noise Shaping, Filter 2, Detect silence On, Gain

set to -0.1dB

Store D DSD2>CD N9 F2

DSD SDIF-2 input to CD format, 9th order Noise

Shaping, Filter 2, Detect silence On, Gain set to

-0.1dB.

Store E AES1 Au MC>DSD2

Auto input on AES1, Multi-Channel Sync On, to

DSD SDIF-2, Filter 5.
Store F AES1 Au MC>24 96

Auto input on AES1, Multi-Channel Sync On, to

24/96 single wire.
Store G AES1 Au>192DA

Auto input on AES1 to 24/192 Dual AES.
Store H AES1 Au>DSD2 F5

Auto input on AES1 to DSD SDIF-2, Filter 5.
Store I QA Au>DSD2 F5

Auto Quad AES input to DSD SDIF-2, Filter 5.
Store J DA Au>24 96

Auto Dual AES input to single wire 24/96.
Store K AES1 Au>CD N9F2

Auto input on AES1 to CD format, 9th order Noise

Shaping, Filter 2, Detect silence On, Gain set to

-0.1dB.

Store L AES1 Au FC>DA96

Auto (96kS/s) input on AES1 to Dual 24/96,

Format Conversion On.

Recalling a Setup

Stored setups may be recalled from memory at any time. Press the Recall
button once to display the list of user-defined setups:

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Either select one of these or press the Recall button again to toggle between
the user-defined and fixed setups:

Scroll up or down to the required store and press the Enter button. A message
window will appear in the display to confirm that the unit is reading the setup.
When complete, the display shows the Status screen for the current menu.

If you make a mistake during a Store or Recall routine and you have not yet
pressed Enter, you can abort it by pressing any of the 4 Operation buttons.

Locking Out Changes, and Unlocking Again

Once the unit is set up, it may be locked against casual interference by holding
down the Status button and pressing the Store button.

appears on the right hand side of the Status, Error Monitor, Test

Mode, Info, Bit Activity Monitor or Level Meter screen as appropriate and the

front panel controls have no effect.

To restore normal operation, hold down the Status button and press the Edit
button. The

resumed.

label will disappear and normal operation will be

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HE HARDWARE

T

ONTROLS AND CONNECTORS

– C

Rear Panel

AES / EBU INPUTS

PUSH PUSH PUSH PUSH PUSH

AES 1 AES 2 AES 3 AES 4

AES / EBU OUTPUTS

All input and output connectors are mounted on the rear panel. Individual
connectors are identified by the panel legend.

Signal Inputs

AES/EBU Digital Inputs 3 pin XLR Female (4 off – AES 1 – AES 4)

Used for AES3 format signals. AES 1 and AES 2 are used together in Dual

AES mode. All four inputs are used together for Quad AES or DSD Quad

modes.

AES / EBU REFERENCE LOOP SPDIF

IN OUT

AES CLK OUT SYNC INPUT

IN OUT

Figure 17– Rear Panel

CH1 IN

RCA

BNC

TOS

WCLK IN

CH1 OUT

DSD / SDIF

LOOP IN

CH2 IN

LOOP OUT

CH2 OUT

WCLK OUT

REMOTE

See base for
serial number

dCS 974

[e-mail]

IN

Disconnect mains
before removing cover.
See User Manual for
installation instructions
before connecting supply.

LOOP

WARNING: This unit

OUT

MUST be earthed.

MAINS FUSE (2AT) ON OF F

V 50/60Hz 20W

AES/EBU Reference Loop 3 pin XLR Female / Male (AES Ref Loop IN & OUT)

Loop IN is used for AES3 references and also for Sync Link operation in multi-

channel synchronising. Loop OUT is hard-wired to Loop IN, allowing the
reference to be daisy-chained through several units.

Sync Input BNC

This is intended for future enhancements.

SPDIF Inputs Various (3 off – RCA IN, BNC IN, TOS IN)

Used for SPDIF inputs. Pull the plastic dust cover out of the TOS input before
use.

DSD/SDIF Input BNC (4 off – CH1 IN, CH2 IN, WCLK IN, LOOP OUT)

The upper group of four DSD/SDIF connectors form an input interface. They are
used as a set for SDIF-2 (PCM or DSD) or SDIF-3 (DSD only).

WCLK IN may be used to sync the unit to an external reference wordclock

while taking data from another input. WCLK IN is internally wired to LOOP

OUT, allowing a reference wordclock to be daisy-chained through several units.

When the daisy-chain is not used, the LOOP OUT connector must be fitted with
a 75Ω BNC terminator. WCLK IN will also accept a 10 MHz GPS reference.

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Signal Outputs

AES/EBU Digital Outputs 3 pin XLR Male (4 off – AES 1, AES 2, AES 3, AES 4)

Used for AES3 format signals. AES 1 and AES 2 (or AES 3 and AES 4) are
used together in Dual AES mode. All four outputs are used together for Quad
AES or DSD Quad modes. In single AES modes, AES 2, AES 3 and AES 4
outputs follow the AES 1 output.

AES/EBU Clock Output 3 pin XLR Male (1 off – AES CLK OUT)

AES CLK OUT carries an AES3 clock signal at the same sample rate as the
AES 1 output. It is used for synchronising equipment connected to the outputs

of the unit.

SPDIF Outputs Various (3 off - RCA OUT, BNC OUT, TOS OUT)

Used for SPDIF outputs. Pull the plastic dust cover out of the TOS output before
use.

DSD/SDIF Output BNC (3 off – CH1 OUT, CH2 OUT, WCLK OUT)

The lower group of three DSD/SDIF connectors form an output interface. Used
as a set for SDIF-2 (PCM or DSD) or SDIF-3 (DSD only) outputs.

WCLK OUT carries Wordclock at the same rate as that appearing on the AES 1

output. It may be used to synchronise equipment connected to any of the dCS
974 data outputs.

(The lower LOOP IN connector is intended for future enhancements.)

Control and Power

Remote 9 pin D type Female (2 off, Remote In and Loop Out)

For remote control via a PC, and/or downloading software updates. Remote In
and Loop Out sockets allow daisy chaining of several different dCS units from
one PC COM port.

Mains Supply 3 pin IEC (CEE22)

Switched, fused and filtered IEC power inlet, for a 50 or 60 Hz AC supply.

Additional Information

As well as connectors, the rear panel displays the following information about
the unit, near the mains supply connector:

Mains Voltage The actual voltage setting supplied.
Model Number dCS 974
Manufacturers Name and Country of origin (dCS Ltd, UK)

The underside of the unit will have a label on that contains a number such as
974-4B1-6B2-2A1-3A2-12345. This is the unit serial number, but it also contains
vital configuration information. We will need this number (all of it) to give you
support over the phone, or to ship software updates to you.

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Front Panel

BIT

4

2

192

kS/s

Power

DSD

Direct Stream Di gital

dCS 974

Power Indicator

OPERATION

Status Se t

MEMORY

Recall Edit Store Enter

D to D Converter

Because of the many options on the dCS 974, we have used a menu based
system to control it. The hardware buttons and knobs below navigate you
through it.

The LED in the top left hand corner lights when power is applied.

Figure 18 – Front Panel

Dither

Noise shap ing

L/R flip

Phase

Gain

Balance

Unlocked

dC S

Data Conversion Systems

OPERATION buttons

MEMORY buttons

LCD display

The bank of 4 buttons in the top left hand corner are the Operation buttons and
are used for navigating around the menu tree:

Status returns the display to the status information screen

to allow a rapid check of key settings.

←←←←

selects the previous (higher) menu level.

→→→→ selects the next (lower) menu level.

Set implements the selected menu item.

The bank of 4 buttons in the lower left hand corner are the Memory buttons and
are used for storing and retrieving setups:

Recall allows one of ten stored setups to be selected

ready for loading.

Store allows one of ten locations to be selected as the

location for saving the current setup.

Edit is used to change the name of a saved setup.
Enter loads or saves a setup.

The backlit LCD display in the centre of the panel can display up to 8 lines of
information.

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LED indicators

A group of LED indicators to the right of the LCD display gives a level of status
indication:

Dither is lit if any Dither is selected.
Noise shaping is lit if any Noise Shaping is selected.
L/R flip indicates that the channels are flipped.

Two Phase LEDs indicate if either or both channels are phase

inverted.

Gain is lit if the setting is other than unity gain (i.e. 0dB).
Balance is lit if the channel balance is shifted from centre.
Unlocked is lit if the unit is not locked to a valid digital input.

Rotary encoder

Turn the knob to move up down the menu tree, adjust parameter values or edit
store names. You may select whether clockwise rotation moves the cursor up or
down - see the section on Display Customise, page 50. The unit is shipped
with the cursor moving downwards by clockwise rotation of the knob and all
instructions in this manual refer to a unit in this configuration. We recommend
turning the knob at a steady speed, rather than trying to turn it as fast as
possible.

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dCS 974

TECHNICAL INFORMATION

Digital Data Formats Supported

dCS 974 provides nine digital data i/o formats:

AES/EBU (often referred to as AES3) for PCM operation
Dual AES (part of the AES3 spec) for PCM operation
Quad AES (part of the AES3 spec) for PCM operation
SDIF-2 for PCM operation
SDIF-2 for DSD operation
SDIF-3 for DSD operation
DSD Quad for DSD operation
SPDIF (electrical) for PCM operation
SPDIF (optical) for PCM operation

For all formats, the incoming Channel Status and User messages are
discarded
bits to be edited.

The enhanced AES/EBU interface is fully implemented. Each channel has its
own parity and data validity bit, as well as User and Channel Status messages.
Cyclic Redundancy Counts (CRC's) are generated from the Channel Status
message.

The Dual AES interface allows an 88.2 or 96kS/s 24 bit signal to be coded as
two standard 44.1 or 48kS/s 24 bit AES data streams, recorded as four tracks
on a recorder with standard capacity, replayed and decoded back into a single
data stream. Operation of the Dual AES interface at double speed allows the
unit to input or output 2 wire 176.4 or 192 kS/s 24 bit data, and convert to and
from this.

12

. The unit allows the AES/EBU and SPDIF output Channel Status

The Quad AES interface allows an 176.4 or 192kS/s 24 bit Dual AES data
stream to be coded as four standard 44.1 or 48kS/s 24 bit AES data streams,
recorded as eight tracks on a recorder with standard capacity. It may be
replayed and converted into a Dual AES stream, a single wire format or DSD.

SDIF-2 PCM message bits are internally set to zero, with the exception of the
block code, which is implemented.

The SPDIF interface has no CRC's - as per definition. Data formats for both
SPDIF electrical and SPDIF optical are identical.

DSD has, at the time of writing, no messaging structure. Contact dCS for more
details. Data formats use either the SDIF-2 system (two data channels and
third clock channel), the SDIF-3 format (two data channels with embedded
clock) or the DSD Quad format (four AES3 style data streams).

12

At present we do this because there is no standard on what to do with the excess or shortage of bits that is

created by a sample rate change. If this causes you a problem, call us – we can probably do something else,
if we are clear what that ought to be.

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DSD

Filter Options

DSD is a single bit very high sample rate (2.822 MS/s) format, where the single
bit words are heavily noise shaped to push noise energy above the audio band.
The frequency response is very high (well above 100 kHz) although at these
high frequencies, noise is also present.

For SACD purposes, 0 dB0

is set at 6 dB below the peak to peak level one

DSD

might expect a full scale sinewave to occupy – this ensures that artefacts that
begin to occur at the limits of the DSD amplitude range do not move down into
the audio band. The 0 dB0

level is shown graphically in Figure 39, page 98.

DSD

The dCS 974 offers a number of different DSD modulators – as Filter options.
All the modulators have the same signal frequency response. They differ in the
way they shape the out-of-band Q noise, and in how far they suppress the

in-band Q noise. Filters 1 to 5 suppress Q noise at least 120 dB below the
nominal 0dB DSD signal, which is one of the marketing specs for SACD.

Filter Comments SQNR

Stability Description

(20 kHz,

dB)

1

High SQNR, high stability 126.14 1.7*10

2

High SQNR 127.23 8.2*10

3

High SQNR, very high

124.66 1.5*10

stability

4

Extremely high stability 122.07 3.0*10

5

Reduced 100k noise 122.27 7.1*10

6

Single complex zero 110.78 3.7*10

7

Real zeros 101.5 2.0*10

10

8

11

12

10

11

10

Two complex

zeros

Two complex

zeros

Two complex

zeros

Two complex

zeros

Two complex

zeros

Single

complex zero

Real zeros

only

Table 4 – DSD Filter Summary

Signal to Q Noise and SACD Specs

Although 120dB SNR over the 0-20 kHz band is a good target, it does not
match the ears response that well. The F weighted curve is currently accepted
as a good model for the ear, and we can use this to weight the noise produced
by the various filter choices. Such a weighting is shown in Figure 38 on page

98, and DSD gives very good performance using such a weighting (better than

23 bit pcm)

The figure shows that Filter 6 and 7 give more F weighted Q noise suppression
in the audio band than Filters 1 to 5. Filter 6 gives around 20 dB more
suppression than Filters 1 to 5 under all circumstances and Filter 7 gives 20dB
more suppression below 10 kHz.

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SACD13 specifies ultrasonic noise in two bands. These are specs informative
specs E2 and E3, and filter performance for a number of specs including these
are given below. The measurements given have been made using a Fourier
Transform based method.

Filter Comments SQNR

DSD Data Formats

DSD is supported on SDIF-2, SDIF-3 and DSD Quad formats.

1

High SQNR,

SQNR

(20 kHz,

dB)

F weighted

(

dB)

126.14 -136.56 -25.98 -28.96

E2 spec

(dB)

high stability

2

High SQNR 127.23 -138.76 -25.85 -28.95

3

High SQNR,

124.66 -134.38 -27.32 -30.49
very high
stability

4

Extremely high

122.07 -129.91 -25.54 -29.53
stability

5

Reduced 100k

122.27 -130.14 -27.13 -31.99
noise

6

Single

110.78 -151.02 -25.19 -23.55
complex zero

7

Real zeros 101.5 -132.41 -25.29 -27.04
SACD Spec -20.00 -28.00

Table 5 – DSD Filter Performance

E3 spec

(dB)

13

Super Audio CD System Specifications, Part 2, Audio Specifications, available from Philips System Standards

and Licensing, Licensing Support, Building SFF-8, PO Box 80002, 5600 JB Eindhoven, The Netherlands.

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PCM Input and/or Output Performance

Filtering

The normal filtering considerations of passband ripple, cutoff frequency and
rate, out of band (stop band) suppression, and transient/phase response apply
to sample rate converters.

The dCS 974 uses linear phase FIR filters to avoid the limit cycle problems that
come with many IIR filters. Linear phase gives filters a symmetrical transient
response before and after a transient (“pre-ringing” and “post ringing”). The
passband may or may not have a ripple
filter being used. Cutoff frequency is >40% of the lowest sampling rate used in
the conversion (input or output).

15

but varies with conversion, and can be as low as –130 dB. The frequency
responses of two commonly used conversions (96kS/s ⇒ 44.1kS/s and 48kS/s
⇒ 44.1kS/s) are shown in Figure 41 and Figure 40 on page 99.

The transient responses of the filters in the 96 kS/s ⇒ 44.1 kS/s conversion are
shown below.

14

, depending on the conversion and/or

The stop band is typically below –110 dB,

Figure 19 – Transient Performance of 44.1 kS/s Filter Options

Use of higher sample rates gives much tighter transient response, with much
less energy smeared into the pre and post ringing. The transient responses of
the 96 kS/s output filters are shown below:

14

Filters always have some ripple. For “zero ripple” filters this is in the µdB to pdB region.

15

For conversions where the lowest rate used is 16 kS/s, 22.05 kS/s or 24 kS/s some conversions cut off at 33%

of the lowest sample rate.

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Figure 20 – Transient Performance of 96 kS/s Filter Options

Spurs

Sample rate conversion is a linear process, so spurs are not caused by
mechanisms that produce harmonic distortion. Spurs
images of the baseband input signal aliasing back into the output

16

are caused by high order

17

. The filtering

in the converter has to suppress these.

We measure these spurs for a 1 kHz input signal – typical values are given in
dB0 for a -1dB0 sine wave in the table below. The blank cells are two pass
conversions, where the performance depends on both conversions.

Rate

11.02

(kS/s)

11.025 -130 -122 -143 -117 -136 -140

12 -139 -136 -131 -135 -138 -137

16 -132 -119 -132 -119 -112 -130 -137

22.05 -137 -145 -124 -134 -130 -134 -113 -139

24 -121 -134 -127 -142 -137 -128 -129 -134

32 -128 -133 -123 -131 -107 -134

44.1 -132 -120 -124 -133 -145 -125 -136 -126 -127 -109 -132 -119

48 -118 -132 -136 -119 -134 -125 -137 -136 -127 -130 -132

88.2 -129 -120 -119 -135 -120 -125 -137 -145 -139 -121 -117 -105

96 -97 -126 -138 -116 -135 -139 -117 -137 -119 -139 -117

176.4 -137 -134 -135

192 -128 -130 -139 -131 -135

12 16 22.05 24 32 44.1 48 88.2 96 176.4 192

5

Output Sample Rate (kS/s)Input

Table 6 – Typical Spurious Level vs Conversion

16

Spurious products

17

For example, a 1 kHz tone with a 48 kS/s sample rate in will produce spurs at 2.9 kHz and 4.9 kHz, 6.8 kHz

and 8.8 kHz, etc, with a 44.1 kS/s sample rate out.

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Noise

Noise arises from processing rounding errors, and from stop band performance.
It is typically around –130dB0, but depends on the conversion being used.

Group Delay

The conversion process takes time, and the time is dependent on the
conversion being carried out, and the filters used. Typical values in
microseconds are given for four conversions in the table below.

Group Delay (µµµµs) Sample Period (µµµµs)

Conversion Filter1Filter2Filter3Filter

Input Output

4

44.1k ⇒⇒⇒⇒ 96k

88.2k ⇒⇒⇒⇒ 44.1k
96k ⇒⇒⇒⇒ 44.1k

96k ⇒⇒⇒⇒ 48k

1141 1131 1131 1131 22.676 10.417
1024 11.338 22.676
1515 1065 1065 1065 10.417 22.676

868 958 1028 948 10.417 20.833

Table 7 – Group Delays, PCM to PCM transitions

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Clocking

The sample clock quality significantly determines the output performance of a
DDC, in as far as items connected may have to reconstitute an analogue signal,
and may ultimately derive their clock from the DDC clock.

The highest quality clocks that are available are crystals, so we use these. In
Internal sync mode, the dCS 974 uses one of two on-board voltage controlled
crystal oscillators (VCXOs) as clock sources – one for 48 kS/s related outputs
and one for 44.1 kS/s related outputs.

The internal VCXO is synchronised to the sync source (which need not be the
signal input) by a phase locked loop (PLL). The PLL is of a special narrow
bandwidth type, that provides a significant degree of "clock cleaning" - but even
so, signal quality may degrade if particularly poor slave clocks are used. A
consequence of the narrow bandwidth is that it takes quite a long time for the
PLL to lock to a new clock frequency – of the order of 2 seconds. The PLL uses
DSP assistance to keep this time acceptable.

The input data is extracted using an oversampled UART type of decoder. This
can tolerate quite jittery inputs, whose phase is unrelated to the clock source
used for locking. The average frequency must be the same, however.

Internal clock

Accuracy when shipped ± 10 ppm
Long Term Stability ± 10 ppm/year at room temperature
Temperature Stability ± 15 ppm over operating temperature range

Synchronising to source

Pull in range ± 300 ppm about nominal frequency
Lock in time < 2 seconds for most combinations

The PLL is very robust, and will lock to very poor signals if necessary. Data is
decoded using a much wider band (faster) PLL, so AES3 type low frequency
jitter on the input clock can be handled, and will be cleaned.

If you need to synchronise several items of digital equipment, we recommend
using a dCS 992 Master Clock.

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Sample Alignment

The dCS 974 aligns samples such that SDIF WCLK OUT aligns with AES3
samples out, the rising edge of wordclock aligning with the start of the first
illegal code in the X,Z subframe preamble and the falling edge aligning with the
start of the Y subframe preamble.

Figure 21 – Wordclock and AES3 outputs, 96 kS/s

Figure 22 – Wordclock and AES3 outputs, 44.1 kS/s

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When SDIF WCLK IN is used as a sync source, in and out are related as
below. The lower waveform is the output, the upper one is the input.

18

For

44.1 kS/s, out leads in by about 500 ns, and for 96 kS/s it is about 230 ns.

Figure 23 – Wordclock in to Wordclock out, 96 kS/s

Figure 24 – Wordclock in to Wordclock out, 44.1 kS/s

If tighter alignment of WCLK IN to WCLK OUT is needed, consider using a
dCS 992 Master Clock, where the phase of individual word clock feeds is
adjustable, or contact us.

18

If this misalignment causes you a problem, please contact us.

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AES3 in and out are related as below, where they are at the same sample rate,
and the AES3 input is used as a sync source. The alignment is better than
40ns. Input is at the top of the displays, output is at the bottom. Signals are at
the sockets on the dCS 974.

Figure 25 – AES3 in to AES3 out, 96 kS/s

Figure 26 – AES3 in to AES3 out, 44.1 kS/s

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DSD data out is aligned to Wordclock transitions, as below – the wordclock
edges align with the data transitions, rather than in the middle of the data eye.
If you need them the other way round, use an additional 10m of cable in the

WCLK OUT path.

Figure 27 – DSD data and Wordclock out

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Multiple Channel Sync’ing

Multiple channel sync’ing requires more things to be in sync than two channel
work - the PLL must not be dual modulus, the DSP algorithm must load with a
constant group delay, and the frame and block syncs must agree.

The dCS 974 meets all these constraints with the addition of a syncing signal
transmitted from a master unit to subsequent slave units. To do this, it passes
information in the User Bits of the AES3 message. To slave adequately, units
must have this sync information input to the AES Ref Loop Input, via a sync
link. Each slave will generate a copy, based on its own timing, for transmission

to the next unit in the chain. If the Multi-channel Sync option is set to On in the

Sample Rate Conversion menu, any units with no user bit synchronisation

data into its AES Ref Loop Input will become a Master. If user bit
synchronisation information is fed in, it will become a slave. Either unit will
output synchronisation information via its AES CLK Output. A master clock
(dCS 992
being used, this system is best, as it avoids any tolerance build up. Connections
are shown in the multi-channel syncing applications, starting on page 29.

Using the multi-channel sync mode, the timing of the data at the output of the
dCS 974 is related to the data coming in. If three dCS 974 units are used in a six
channel set up, and the data into all of them is bit sync’d from (say) a six
channel source, the outputs will be bit sync’d. If the inputs are not quite bit
aligned, then the outputs will not quite be bit aligned. If the inputs are way off in
phase but frequency locked, the outputs will be way off in phase but frequency
locked, and the timing of the block structures of the several output signals will
not be defined.

19

) can be used as the master – if more than about 8 channels are

Sample Rate (kS/s) Time in

input

sample

rate UI’s

Basic dCS 974 unit to unit

20

± 0.3 ± 50 ± 24

output timing alignment.
Input misalignment allowed,

± 2 ± 334 ± 162
with all inputs at the same
frequency, for block
structuring to work (no
Master Clock).

Input misalignment allowed,

± 4 ± 668 ± 324
with all inputs at the same
frequency, with Master Clock

Input misalignment allowed,

± 64 ± 11338 ± 5208
with all inputs at the same
frequency, with Master Clock
as in Figure 1621.

Table 8 – Multiple Channel Sync mode – allowable input misalignment

The scope shots below show the timing relationships between two units, using
the sync link, for various conversions. They are taken from 2 units, with scope
probes on the same point in each unit. The units are linked by a sync link.

19

version 2.0 software or higher.

20

UI = Unit Interval, see AES3 spec. There are 128 UI’s per sample in AES3.

21

Master Clock can adjust its Wordclock phases as necessary.

Time in ns,

44.1 kS/s
input

Time in ns,

96 kS/s

input

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Figure 28 – 44.1 kS/s to 96 kS/s PCM, showing AES3 alignment

Figure 29 – 96 kS/s to 44.1 kS/s PCM, showing AES3 alignment

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Figure 30 – 44.1 kS/s to DSD, showing DSD bit alignment

Multiple Channel Multiple Sample Rate Synchronising

DVDs can make use of mixed sample rates in their multi-channel mode – for
example, 96 kS/s in the front channels and 48 kS/s in the rear channels.

As well as the problems mentioned above in the section Multiple Channel

Sync’ing, use of multiple channels brings an additional problem in that the

group delay in the sample rate conversion process varies with the sample rate.
It generally gets longer as the sample rate gets lower, making the rear channels
seem further away than you might want.

Figure 16 shows how a master clock may be used with several dCS 974‘s in

parallel to get simultaneous synchronised sample rates out at the same time.

Please contact dCS if you need support for this process.

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Noise Shaping

The dCS 974 uses noise shaping22 that is optimised to the F weighting curve23.
It does not affect signal frequency or transient response, but shapes the
frequency response of errors (Q noise, or truncation errors) so that they fall as
much as possible in the less sensitive part of the spectrum. The architecture
used also shapes dither, where this is added. For all the major sample rates
(32 kS/s, 44.1 kS/s, 48 kS/s, 88.2 kS/s, 96 kS/s) the noise shapers have been
individually optimised and the first 10 orders are offered. The 1
shapes for 44.1 kS/s agree well with Wannamaker’s published results24.

Noise Shaping adds more noise power, but because of the shaping it is
perceived as lower noise. There is a compromise to be drawn – as more
aggressive shaping is used, more noise is added, and less perceived
improvement occurs. In practice, things stop improving by about the 10
The increased real noise power can cause (small) clicks in editing, if this is
carried out after the shaping. For each major sample rate, we recommend an
aggressive and a gentle setting, below:

st

, 3rd, and 9

th

order.

th

Sample Rate

(kS/s)

32 1

44.1 1
48 1

88.2 1
96 1

Lowest

Order

st

st

st

st

st

Highest

Order

th

10

th

10

th

10

th

10

th

10

Gentle

Shaping

nd

2

nd

2

nd

2

rd

3

rd

3

Aggressive

Shaping

th

6

th

9

th

8

th

7

th

7

Table 9 – Noise Shape Orders by Output Sample Rate

The gentle shaping tends to follow the E weighting curve, by chance. For more
information on this topic, either see Word Length Reduction on page 104 or
read the references below.

22

It actually uses an Error Shaping architecture, but the name is now being used for entirely other things and is

less well known, so we call it, erroneously, Noise Shaping

23

“Minimally Audible Noise Shaping”, S.P.Lipshitz and R.A.Wannamaker, J AES vol 39 no 11, p836-852

24

“Psychacoustically Optimal Noise Shaping”, R.A.Wannamaker, J AES vol 40 no 7/8, p611-620

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Dither

The dCS 974 uses relatively unusual dither generators to achieve the very good
statistics necessary for audio purposes. Many dither generators use PRBS
generators (Pseudo Random Binary Shift register generators). These are well
known, well documented, and very predictable – but unfortunately their statistics
are not that great. The problem shows up as a spectrum that is not flat, and
histograms (PDFs, Probability Density Functions) that diverge from the ideal
quite significantly.

Adding dither adds noise. Top hat dither uses one generator per channel to add
±0.5 lsbs p-p of rectangularly distributed dither, and triangular dither uses two
generators per channel to add ±1 lsbs p-p of triangularly distributed dither. This
is on top of the Q/√12 rms dither from word length reduction in the first place
(where Q is the size of the output word lsb). The noise shaped triangular
setting uses one generator to add ±1 lsbs p-p of triangularly distributed dither
that is frequency shaped, and so has low perceived (weighted) noise power.
This last is a significant test of generator performance – the dCS 974 performs
very well. Performance curves for all these settings, including PDFs of the
added dither, are given in the dCS 974 Performance Curves, page 94.

The noise added by the dither settings is summarised below:

Dither Type Noise

Power

(0-Fs/2)

Added Noise

Power

(unweighted)

Perceived

Noise

Added

(F weighted)

No dither

Q/√12

0 dB 0 dB
(straight truncation)
Top Hat dither
Triangular dither
Noise Shaped Triangular

Q/√6
Q/√4
Q/√4

3 dB 3 dB

4.8 dB 4.8 dB

4.8 dB 1.2 dB

dither

Table 10 – Noise Added by Dither Types

If dither is used, it is shaped (made less audible) by noise shaping. This applies
as much to noise shaped triangular as the others.

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Digital Interface Specifications

AES/EBU (AES3)

Type
Impedance 110 110

Input Output

Balanced, differential

Ω

Sensitivity (unloaded) 1 ~ 10 7 V pk-pk
Maximum Wordlength 24 24 bits
Connector XLR3 female XLR3 male
Connections

Pin 1 Ground or shield
Pin 2 +Signal
Pin 3 -Signal

Table 11 – AES/EBU Interface Electrical Characteristics.

SDIF and DSD

Type

Input

(Upper block)

Single ended, ground

Output

(Lower block)

referred

Impedance 100 (CH1/2)

55

Ω

~1k (WCLK)
Sensitivity (unloaded) TTL TTL
Maximum Wordlength 24 24 bits
Connector BNC x 4 BNC x 3
Connections

CH1 IN CH1 OUT
CH2 IN CH2 OUT

WCLK IN /

WCLK OUT

LOOP OUT

IMPORTANT!

Table 12 – DSD/SDIF Interface Electrical Characteristics.

The upper DSD/SDIF WCLK IN connector loops through to the upper

LOOP OUT connector to allow an external Wordclock to be daisy-chained.

The last unit in the daisy-chain will need a 75

Ω

BNC termination connected

to the upper LOOP OUT.

SPDIF (electrical)

Type

Input Output

Single ended, ground

referred

Impedance 75 75

Ω

Sensitivity (unloaded) 0.5 1.0 V pk-pk
Maximum Wordlength 24 24 bits
Connector RCA Phono & BNC

Table 13 – SPDIF Interface Electrical Characteristics.

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IMPORTANT!

SPDIF (optical)

Type

Input Output

Optical

Maximum Wordlength 24 24 bits
Wavelength 660nm
Connector Toslink EIAJ CP-340

Table 14 – SPDIF Optical Interface Characteristics.

The Toslink interface is not specified for operation at 88.2 or 96 kS/s due to
limitations in the Toslink devices. In practice, the interface has been shown
to operate correctly with other dCS equipment at all sample rates up to
96kS/s but dCS cannot guarantee this due to Toslink manufacturing
variations.

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Message Handling

The dCS 974 strips the message information from the incoming data. The
message in the outgoing data is set using the AES Message Edit and SPDIF

Message Edit menus, located under the Sample Rate Conversion menu.

AES/EBU Message Handling

The AES3-1992 standard was written at a time when only 3 sample rates were
in common use in the audio industry. dCS started manufacture of ADCs
featuring 96 and 88.2 kS/s sample rates in 1993 and we have evolved
modifications to AES3-1992 which accommodate these innovations. These are
currently being considered by the AES.

The AES/EBU interface transmits a data structure that conforms to the dCS
version of AES3-1992. This contains 28 bits of Manchester encoded data, and a
4 bit near-Manchester encoded preamble in a subframe, and subframes are
further assembled in a block and frame structure. Each subframe contains:

• preambles, to allow the receiver to sync up

• up to 24 bits of audio data, transmitted lsb first

• V, a validity bit

• U, a user bit, for the "User Message"

• C, a Channel Status bit, for the "System Message"

• P, a parity bit

IMPORTANT!

The AES/EBU interface and the SPDIF interface have similar data
structures, although the messages are completely different. The two
structures are identified in the data domain by the use of the
Consumer/Professional bit (bit 1 in the message). A "1" indicates AES/EBU
format, a "0" indicates SPDIF format.

The default AES/EBU message attached to the output data by the unit before
being changed by the user is as follows:

Professional: On
Non-Audio: Off
Mode: Stereophonic
Source: DCS1
Destination: null

For more information on the way dCS implement the AES3 system message to
handle higher sample rates, see the Appendix to this manual. For the formal
definition of the AES3 interface, see footnote

25

, from the AES.

25

AES3-1992 (ANSI S4.40-1992) “AES Recommended practice for digital audio engineering – Serial

transmission format for two-channel linearly represented digital audio data”.

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SPDIF Message Handling

IMPORTANT!

The SPDIF interface (sometimes known as the Consumer AES/EBU interface)
transmits a data structure that conforms to the IEC 958

26

standard. Like the
AES/EBU, this contains 28 bits of Manchester encoded data, and a 4 bit near­Manchester encoded preamble in a subframe, and subframes are further
assembled in a block and frame structure. The difference lies only in the voltage
levels, and the Channel Status bits (the System Message). It contains 24 bits of
audio data.

The AES/EBU interface and the SPDIF interface have similar data
structures, although the messages are completely different. The two
structures are identified in the data domain by the use of the
Consumer/Professional bit (bit 1 in the message). A "1" indicates AES/EBU
format, a "0" indicates SPDIF format.

The default SPDIF message attached to the output data by the unit before
being changed by the user is as follows:

Professional: Off
Non-Audio: Off
Copy Permit: On
Format: 2-Channel General Format

26

See EN 60958:1995 or IEC 958:1989 with amendments 1&2. The structure of the message is sufficiently

complex that it is best to read the source material.

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SDIF-2 Message Handling

The SDIF-2 interface is a 4 wire NRZ interface - so the DC level on each signal
line may not be constant. It contains 20 bits of audio data and has a block
structure of 256 stereo samples, rather than the 192 of AES/EBU. There are 8
bits of message per channel per sample - with a further 3 bits being used for an
"illegal code" based sync code. Of the 8 bits per sample, the 8 in the first
sample are reserved for system messaging, and the rest are for User
messages.

The 4 wires are:

Ground return
Left Channel
Right Channel
Wordclock

The sync codes enable data recovery without the word clock, if necessary, but
with the number of data formats in current operation, this method of locking is
strongly discouraged.

The SDIF-2 message is given in the table following. The dCS 974
implementation sets all bits of the User message to "0".

DESCRIPTION Definition Default

Undefined 0000 0xxx 0000 0xxx

Emphasis

No emphasis
Emphasis (15µsec, 50µsec)

Dubbing Prohibit

Dubbing allowed
Dubbing inhibited

Block Code

Start of block
Not start of block

SDIF-3 Message Handling

At present, no messaging is implemented in SDIF-3.

Table 15 - SDIF-2 Message Table

xxxx x00x
xxxx x01x

xxxx xxx0
xxxx xxx1

xxxx xxxx 1...
xxxx xxxx 0...

Message

xxxx x00x

xxxx xxx0

as required
as required

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Power Consumption

The dCS 974 has a linear power supply, and so power consumption changes as
the supply voltage changes. The internal regulation is comparatively efficient for
a linear supply, so these changes are kept to a minimum. Consumption is
independent of supply voltage setting.

Power Consumption with Supply Voltage (measured as AC power into mains
socket):

Nominal voltage 16 W

Voltage -10% 14 W
Voltage +10% 17 W

The actual intended supply voltages are shown on the rear panel. 50Hz or 60Hz
operation is not important – the unit can use either. In general, users will not
need to change the mains input configuration. If you do need this to be done,
please see the section Having Your Options Changed, page 114 in this
manual and contact your distributor or dCS.

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Size, Weight and Operating Conditions

Size and Weight

The dCS 974 dimensions correspond to a standard 2U 19" rack mount case.
Four heavy duty feet, fitted to the base, extend the overall height to slightly
greater than 2U.

Dimensions

Width 430 mm see note (i)
Height, without feet 88 mm (2U)
Height, with feet 95 mm
Depth 390 mm see note (ii)
Weight 8.5kg see note (iii)

note (i) Removable 19" rack mount ears are supplied,

taking total width to 483 mm (19").

note (ii) Measured from front panel to rear panel

connectors. Additional depth should be allowed to
accommodate cable connectors. The rotary control
knob protrudes 22mm from the front panel.

note (iii) The high quality case is necessarily heavy,

consideration should be paid to appropriate
support shelving when installing the units in a rack.

Operating Conditions

The case of the dCS 974 has no ventilation slots or fan cooling, to give:

• quiet operation (does not need to be installed in a machine room)

• internal temperature stability

• improved electrical safety

• long term reliability

• no regular maintenance or cleaning requirements

It dissipates relatively low power, so that usually allowing natural convection
provides enough cooling. Do not install the unit near heat sources such as
radiators, air ducts or direct strong sunlight. Ambient should not exceed 50°C,
should not fall below 0°C, and should be non condensing. If in doubt, the easy
test is – the dCS 974 is happy to work anywhere a human is.

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

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dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

dCS 974

PERFORMANCE CURVES

The graphs on the following pages show key performances of the dCS 974.

• Dither PDFs, showing how the dither types are effectively ideal, including

noise shaped triangular dither

• FFTs of the dither signals used (excludes truncation, or Q, noise)

• Raw data for small signal truncated (± 4 lsbs) sinewave, showing source

waveform, no dither, and all dither types. Shows absence of DC offset, and
behaviour of the various dithers

• FFTs of truncated small signal (-90 dB0 sine), showing no truncation,

truncation without dither, and the effect of dithers.

• FFTs of truncated small signal (-90 dB0 sine), with noise shaping, with and

without added dithers.

• DSD spot Q noise for filter options

• DSD integrated Q noise for filter options

• DSD F weighted Q noise for filter options

• DSD 0 dB0 (full scale) signal

• 48 kS/s to 44.1 kS/s conversion, Filter responses

• 96 kS/s to 44.1 kS/s conversion, Filter responses

• Noise shaping curves for 32 kS/s

• Noise shaping curves for 44.1 kS/s

• Noise shaping curves for 48 kS/s

• Noise shaping curves for 88.2 kS/s

• Noise shaping curves for 96 kS/s

• Noise Shaper noise and weighted noise vs shaper order

27

Histograms of Dither Types, before Truncation

0.5%

0.4%

0.3%

0.2%

Fract ion of Time Dither O cc upies Bin

0.1%

0.0%

-384 -256 -128 0 128 256 384

2 million data points

Word length reduced by 8 bits

dCS 972 SW v1.54

Top Ha t

Triangular

Noise S haped Triangular

Code (lsbs)

Figure 31 – Dither PDFs

27

Note that many aspects of the

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are identical to those of the

Page 94

dCS 972

.

Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Dither Only Spectra, no Si gnal

dCS 972 SW v1.54

-110

-120

-130

Ampli tude (dB )

-140

-150

0 2 4 6 8 10 12 14 16 18 20 22

Top Hat dither, actual theoret ic al

Triangular dither, actual theoretical

Noise S haped Triangular dither, act ual theoreti cal

44.1 kS /s sampling, 16 bit dither, 1024 point FFTs, H6 window

Frequency (kHz )

Figure 32 – Dither Spectra (FFTs)

Raw Data for Source and Truncated Small Signal

2048

1024

dCS 972 SW v1.54

0

Amplitude (ls b 24)

-1024

24 bit source data 16 bit truncation
16 bit truncation with Top Hat dither 16 bit truncation with Triangular dither
16 bit truncation with Noise Shaped Triangular dither

-2048
0 128 256 384 512

Sample Number

Figure 33 – Small Signal Raw Data with Dithers

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Spectra of -90dB 24 bit sinewave truncated to 16 bits with dither options

-60

44.1 k S/ s s ampl ing, -90 dB 1.44 kHz
input, 1024 point FFTs , H6 W indow

-80

-100

Ampl itude (dB)

-120

-140

-160

0246810121416182022

dCS 972 SW v1.54

24 bit s ourc e data

16 bit t runca tion, no dit her

16 bit t runca tion, Top Hat dit her

16 bit t runca tion, Triangular dit her

16 bit t runca tion, Nois e Shaped Triangular dither

Frequency (k Hz)

Figure 34 – Truncated small signal FFT, with and without dither

Noise Shaper and Noise Shaper with Dither Performance

-60

16 bit truncation, 10th order noise s haping, no dither

-80

-100

-120

Amplitude, Real Data (dB)

-140

-160

0 2 4 6 8 10 12 14 16 18 20 22

16 bit truncation, 10th order noise s haping, Top Hat dit her

16 bit truncation, 10th order noise s haping, Triangular dither

16 bit truncation, 10th order noise s haping, Nois e Shaped Triangular dither

dCS 972 SW v1.54

44.1 kS /s sampling, 1024 point FFTs, H6 window, -90 dB 1.44 k Hz input ,
10th Order Noise S haping

Frequency (k Hz)

Figure 35 – Truncated small signal FFT, showing noise shaping with and without dither

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Document No: OS-MA-A0124-112.1A1

dCS 974 User Manual Manual for Software Version 1.0x
dCS Ltd May 2001

Spot Q Noise for DSD Filters

0

-20

-40

-60

-80

-100

-120

Q Noise rel F ull Scale DSD (dB)

-140

-160

-180

-200
1 10 100 1000

in 400 Hz bandwidth

F1
F2
F3
F4
F5
F6
F7

-120dB in 20 kHz

Frequency (kH z)

Figure 36 – DSD output, spot Q Noise for the various Filter options

Integrated Q Noise for DSD Filters

20.00

0.00

-20.00

-40.00

-60.00

-80.00

-100.00

Integrated Q Noise Power (dB)

-120.00

-140.00

-160.00

-180.00

1 10 100 1000

normalised for Full Scale DSD at 0dB

Frequency ( kHz)

F1

F2

F3

F4

F5

F6

F7

Figure 37 – DSD Output, integrated Q Noise for the various Filter options

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(rig

)

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Spot Q Noise for DSD Filters, F Weighted

in 400 Hz band width

-80

F1

-100

-120

-140

-160

-180

-200

Q Noise rel F ull Scale DSD (dB)

-220

-240

-260

-280

0.1 1 10 100 1000

Frequency ( kHz)

F2

F3

F4

F5

F6

F7

F weighting curve

ht hand scale

Figure 38 – DSD Output, F weighted Q Noise for the various Filter options

20

0

-20

-40

-60

-80

-100

-120

-140

-160

-180

F weighting (d B)

DSD Format, showing Full Scale Signal

1.5

1

0.5

0

-0.5

-1

-1.5

0 50 100 150 200 250 300 350 400 450 500

dCS 972 SW v1.54

Time (usecs)

Figure 39 – DSD showing 0 dB0 (full scale)

DSD has only two levels – printer artefacts make it look like more

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48 kS/s to 44.1 kS/s Filters

dCS 972 SW v1.54

0 2 4 6 8 10121416182022242628 3032343638404244

0.100

0.075

0.050

0.025

0.000

-0.025

-0.050

-0.075

-0.100

-0.125

-0.150

-0.175

Zoomed Pass band Respons e (dB)

-0.200

-0.225

-0.250

-0.275

-0.300

0 4.41 8. 82 13. 23 17. 64 22.05 26.46 30.87 35.28 39.69 44. 1

Normal axis ax is - to right

Zoomed axis - to left

Filt 1

Filt 2

Filt 3

Filt 4

Frequency (kHz )

10

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

-120

-130

-140

-150

Respons e (dB)

Figure 40 – 48 kS/s to 44.1 kS/s conversion, Filter responses

96 kS/s to 44.1 kS/s Filters

dCS 972 SW v1.54

0 2 4 6 8 10 1214161820222426283032343638404244

0.100

0.075

0.050

0.025

0.000

-0.025

-0.050

-0.075

-0.100

-0.125

-0.150

-0.175

Zoomed Pass band Respons e (dB)

-0.200

-0.225

-0.250

-0.275

-0.300

0 4.41 8. 82 13.23 17.64 22.05 26.46 30. 87 35.28 39.69 44.1

Normal axis - t o right

Zoomed axis - to left

Filt 1

Filt 2

Filt 3

Filt 4

Frequency (kHz )

10

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

-120

-130

-140

-150

Pass band Response (dB)

Figure 41 – 96 kS/s to 44.1 kS/s conversion, Filter responses

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32 kS/s Noise Shape Plots

24

18

dCS 972 SW v1.54

12

6

0

-6

Noise Amplitude relative to No Shaping (dB)

-12

-18

-24

0 4 8 12 16

2nd or 6th Order Recommended

Frequency (kHz)

Figure 42 – 32 kS/s noise shaper curves

44.1 kS/s Noise Shape Plots

dCS 972 SW v1.54

36

30

24

Order 1

Order 2

Order 3

Order 4

Order 5

Order 6

Order 7

Order 8

Order 9

Order 10

18

2nd or 9th Order Recommended

12

6

0

-6

`

-12

-18

Noise Amplitude relative to No Shaping (dB)

-24

-30

Orde r 1

Orde r 2

Orde r 3

Orde r 4

Orde r 5

Orde r 6

Orde r 7

Orde r 8

Orde r 9

Order 10

-36
0 4 8 121620

Frequency (k Hz)

Figure 43 – 44.1 kS/s noise shaper curves

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