Alesis EC2 User Manual

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EC-2

96kHz Sample Rate Upgrade

A/D and D/A Converter Cards

for the ADAT HD24 Hard Disk Recorder

OWNERSMANUAL

VERSION1.0

APPLIES TOADAT HD24 SOFTWAREVERSION1.05 AND ABOVE

EC-296kHz A/D/D/A upgrade• appendix A

© 2002 Alesis. All rights reserved. Reproduction in whole or in part is prohibited. Specifications Subject To Change Without Notice.

7-51-0107-A6/2002

EC-2Manual

appendix A

EC-296kHz Upgrade Cards

This document covers only those aspects unique to the EC-2cards and should be kept with the HD24 manual.

Table of Contents

 

Important Safety Instructions ................................

2

Safety symbols used in this product .......................

2

CE Declaration of Conformity................................

2

About the EC-2.....................................................

2

Installing the EC-2into the HD24...........................

3

Using the EC-2 .....................................................

6

Inputs and Outputs...............................................

7

About the EC-2’saudio performance......................

8

When to use 88.2/96 kHz ......................................

8

Extending the frequency range of other studio

 

equipment....................................................

10

Using the HD24/EC-2with computer

 

workstations and digital mixers.....................

11

Using the HD24/EC-2with the AlesisAI-4

 

AES/EBU Interface.......................................

12

Specifications .........................................................

13

Index

 

12-channeloperation................................................

6

AES/EBU Digital Audio Interface...........................

12

Analog Input (A/D) board .......................................

5

Analog Output (D/A) board ....................................

5

Antialiasing filters ...................................................

8

anti-static

 

during installation .............................................

4

converters ...............................................................

8

daughterboard ........................................................

3

DC power cable .......................................................

6

Digital inputs and outputs

 

at high sample rates ...........................................

6

digital mixers

 

at high sample rates .........................................

11

dynamic range.........................................................

8

Latency .................................................................

11

level change

 

in unbalanced input...........................................

7

low-passfilters ......................................................

10

MasterLink

 

exporting to.....................................................

12

microphones .........................................................

10

MIDI sequencer .......................................................

2

mixing consoles .....................................................

10

monitors

 

at 96 kHz.........................................................

10

Nyquist theorem......................................................

8

oversampling filters .................................................

9

phase response ........................................................

9

sample rates

 

about ................................................................

8

software

 

upgrade ............................................................

2

Synchronizing .........................................................

7

Word clock............................................................

12

workstations..........................................................

11

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EC-296kHz A/D/D/A upgrade• appendix A

Important Safety Instructions

Safety symbols used in this product

This symbol alerts the user that there are important operating and maintenance instructions in the literature accompanying this unit.

This symbol warns the user of uninsulated voltage within the unit that can cause dangerous electric shocks.

All safety warnings in the HD24 manual (pages 7 through 10) apply to the EC-2as well.

CE Declaration of Conformity

For the CE Declaration of Conformity, please visit the Alesis web site at: www.alesis.com

About the EC-2

The EC-2is an optional 96kHz sampling rate analog hardware upgrade designed exclusively for the Alesis ADAT HD24. It provides 24 simultaneous channels of balanced +4 dBu analog audio inputs and outputs via 48 1/4” TRS type jacks. TheEC-2is installed directly inside the HD24’s rear panel, in place of the original A/D and D/A boards, for simple system integration and flexibility. With theEC-2installed, the HD24 can record and play back digital audio at the 96kHz or 88.2 kHz sampling rates (in addition to the standard 44.1 and 48 kHz rates) via its analog inputs and outputs. In high sample rate mode, the HD24 can record and play back up to 12 tracks at a time.

The EC-2expansion cards are designed for use only with HD24 software version 1.05 or higher. If your HD24 has a lower software version, visit our web site at www.alesis.com to download the latest HD24 software and instructions for updating the HD24 via a standard MIDI file or via Ethernet. If you don’t have a computer or MIDI sequencer, contact your Alesis dealer or local service center to help you with the upgrade.

The EC-2upgrade boards are a replacement for the standard HD24 analog converter boards. They do everything the standard boards do, plus:

24 channels of High Performance 24-bitAnalog Audio Conversion.24 channels of simultaneous input and output on 1/4” TRS jacks. Superior DACs and ADCs allow the EC-2 to considerably surpass the standard converter boards in THD+N and dynamic range.

Support for Sample Rates up to 96kHz. The EC-2 boards allow you to use analog inputs and outputs at 88.2kHz and 96kHz nominal sample rates.

Simple hookup and operation. The EC-2 is designed to install in the rear panel of the HD24 and connects to the main circuit board with the included multi-pin ribbon connectors. Once connected, the HD24 will detect the cards’ presence, and allow you to select analog inputs as the source when using the 88.2kHz and 96kHz sample rates.

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EC-2Manual

appendix A • EC-296kHz A/D/D/A upgrade

Installing the EC-2into the HD24

Precautions

The EC-2boards should only be installed by a dealer or trained technician. End users should only attempt installation if they have experience with this type of procedure. If any of the following instructions are not clear to you, please have a dealer or trained technician install it for you. Improper installation by the end user may damage the boards and/or your HD24 and may void your warranty.

Packing List

In the EC-2box, you should find the following items:

This manual (P/N 7-51-0107,E2 User’s Manual)

96 kHz Analog Input board (P/N 9-40-0256,E2 A/D PCB)

96 kHz Analog Output board (P/N 9-40-0257,E2 D/A PCB)

Daughterboard (P/N 9-40-0258,E2 D/D PCB)

DC power cable (P/N 4-74-0031,E2 DC Power Cable)

Before you begin, verify that you have everything in this packing list. When you unwrap the components, save the packing materials so you can use them to store the original parts.

Overview

In the HD24, the conversion between analog and digital signals takes place on two PCBs (printed circuit boards) that are mounted directly to the input (A/D) and output (D/A) connectors that poke through the back panel. In a “stock” HD24 without 96 kHz sampling capability, each card connects directly to the main PCB on the bottom of the unit with a ribbon cable.

To add 96kHz analog recording and playback capability, both the input and output boards are completely replaced, and another board (the daughterboard) is added bridging across them. The daughterboard then connects via ribbon cables to the main PCB. The daughterboard requires a connection to the power supply, so the existing 4- connector power cable must be replaced with a new 5-connectorpower cable.

Tools required

Before you begin, have these tools ready:

#2 Philips-headscrewdriver

14 mm nut driver or socket wrench

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EC-296kHz A/D/D/A upgrade• appendix A

Prepare to install:

1. Disconnect the HD24’s AC power cable, and make sure you are working on a clean, flat, hard surface. Ground yourself by touching a grounded metal object.An anti-static workstation with anti-static mat and wrist strap is highly recommended.

Hazardous voltages are present within the chassis. Do not remove the top panel without first unplugging the unit from AC power!

2.Remove the cover from the HD24: The cover is held to the body with 5 Philips head screws on the rear, 2 on each side, and one on the top. Slide the cover directly towards the rear; don’t lift it up—there are metal tabs on the back panel and along the bottom that will get bent if you do.

HD24 interior with original A/D/A PCBs

A/D PCB

D/A PCB

26-pinribboncables (remove)

Remove the existing converter PCBs and cables:

3.Locate the existing DC power cable. This cable has several thick red, orange, yellow, black, and blue wires bundled together. Pinch the tab lock holding the white connector to the back of Drive 1 and carefully disconnect it. Do the same for the connector on Drive 2, the Main PCB (the printed circuit board on the floor of the HD24), and finally the power supply itself. (This will be replaced with a new cable in step 14.)

4 . Disconnect the 26-pinflexible ribbon cables from the existing converter PCBs and the main PCB, and remove them completely.

New 26-pincables are attached to theEC-2daughterboard—theold ones will not be used.

5.Remove the 24 nuts and washers on the 1/4” input connectors, holding the PCB in place to keep it from falling. Then remove the old A/D PCB (the highest one on the back panel).

6.Do the same for the 24 nuts and washers on the 1/4” output connectors. Hold the PCB in place to prevent the D/A PCB from dropping onto the main PCB. Once the PCBs are removed, put the nuts and washers back on the jacks and store these PCBs and cables in the packaging that the EC- 2 came in.

Main PCB

Power supply

DC power cable (remove)

Drive 1

Drive 2

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appendix A • EC-296kHz A/D/D/A upgrade

Install the new EC-2PCBs

7.Find the daughterboard in the EC-2package: it has two26-pinflexible cables attached to it. Insert the ribbon connector labeled “J4 TO MAIN PCB” on the daughterboard into the 26pin header labeled on the main PCB as “J15 TO A/D PCB”.

8 . Insert the ribbon connector labeled “J3 TO MAIN PCB” on the daughterboard into the 26pin header labeled on the main PCB as “J14 TO D/A PCB”.

The headers on the main PCB sit near the back center, where the old input/output PCBs used to plug in. The red side of each cable should face the right of the HD24 (closest to the fan). Verify that the cables don’t have any twists in them and that there are no unconnected or exposed pins on the headers.

9. Lay the daughterboard gently on the PCBs at the rear of the hard drive cages until the Analog Input and Analog Output PCBs are installed.

10.Get the new Analog Output (D/A) PCB from its packaging. Remove the nuts and washers from the 1/4” connectors on the new Analog Output (D/A) PCB.

NOTE: The Analog Input and Analog Output PCBs look very similar. Verify that you have the correct PCB by looking for the part number and part name in the text in the corner of the PCB.

11.Place the Analog Output PCB in the bottom set of rear panel holes (labeled OUTPUT on the rear panel) with the components facing down (so that you can read the white text on the PCB, which says “D/A PCB” and “Analog Output”). Put a few of the washers and nuts on the 1/4” jacks to hold the PCB in place. Screw them down all the way, but do not tighten yet—itshould be just a little loose.

12.Place the Analog Input PCB in the top set of rear panel holes (labeled INPUT on the rear panel) with the components facing down and put a few of the washers and nuts on the 1/4” jacks to hold the PCB in place. Screw them down all the way, but do not tighten.

HD24 with EC-2installed

Daughterboard PCB

Analog In

A/D PCB

Analog Out

New DC

power cable

D/A PCB

 

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EC-296kHz A/D/D/A upgrade• appendix A

Connect the PCBs

13.Connect the daughterboard to the Input and Output PCBs: Line up the connectors to the bottom (D/A) and top (A/D) PCBs, make sure all the pins line up, then gently push the daughterboard to the rear of the HD24 using the plastic ribbon cable headers as pressure points, making a connection between all three PCBs.

The connectors will only line up in one orientation. Verify that there are no pins unconnected or exposed.

14.Put the remainder of the washers and nuts on the jacks of the input and output connectors and tighten them all down (total 48 jacks).

15.Install the new DC power cable, connecting the power supply, main PCB, daughterboard, and hard drive PCBs as shown in the illustration on the previous page. Run it from the daughterboard to the main PCB to the power supply, then back from the power supply to the two drives. Make sure the connectors snap into place securely.

16.Replace the top panel.

To test for proper installation

After installation, you will be able to select ANALOG input as well as DIGITAL with SAMPLE RATE set to 88.1 and 96kHz.

1.Plug the unit back in to AC power and turn on the HD24.

2.Select or create an 88.2kHz or 96kHz song.

3.Press INPUT SELECT until the “INPUT” group in the alphanumeric display indicates “ANALOG”. This confirms that the HD24 has detected theEC-2’spresence.

If it’s not detected, unplug the unit and check all connections carefully, disconnecting and connecting each, then trying again to see if the EC-2is detected. Contact Alesis Product Support or an authorized service center if the cards are still not detected.

Using the EC-2

For important information about high-resolutionoperation of the HD24, see Chapter 7 of your ADAT HD24 owner’s manual (page 65).

About 96kHz/88.2kHz Sampling Operation

An ADAT HD24 with EC-2upgrade boards installed operates identically to a “stock” HD24 with respect to input arming, selection, and routing (or “normalling”). The only difference is that you will be able to useanalog inputs and outputs when the system is set to 88.2kHz or 96kHz sampling rates. (Without theEC-2,you must use the ADAT Optical digital inputs and outputs with an external 88.2/96kHz converter to record at higher sample rates.)

About 12-channeloperation at high sample rates

When recording and playing back any Song that has been initialized at the 88.2 or 96 kHz sampling rates, the HD24 is limited to recording a maximum of 12 channels.

Analog input channels 13-24will be ignored.

Analog output channels 13-24will duplicate output channels1-12.

Digital inputs and outputs are grouped in fours instead of eights: tracks 1-4on the HD24’sADAT OPTICAL 1-8 ports, tracks5-8on the HD24’sADAT OPTICAL 9-16 ports, and tracks9-12on the

HD24’s ADAT OPTICAL 17-24 ports. For more on operation of the ADAT Optical port, see page 66 of the HD24 manual.

When using an HD24/EC-2at the standard 44.1kHz or 48kHz sampling rates, you will still be able to record and play back all 24 tracks. The only difference from the original boards will be improved audio performance, due to the higher quality converters and analog circuitry of theEC-2.

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appendix A • EC-296kHz A/D/D/A upgrade

Synchronizing at high sample rates:

To record more than 12 tracks in the high sample rate mode, simply synchronize two HD24/EC-2units together by linking them with an ADAT Sync cable (see page 24 of the HD24 manual). Up to five HD24s may be synchronized this way, allowinghigh-samplerate systems of up to 60 tracks.

Synchronizing two HD24s at different sample rates:

When synchronizing multiple HD24s (or an HD24 with tape-basedADATs) together, it is possible to have an HD24 record and play back a high sample rate Song, while other machines play back a standard sample rate Song.

In this case, the sample rates must be even multiples of each other (44.1 with 88.2 or 48 with 96 kHz).

For example, one HD24 can be running with 24 tracks of instrumental tracks at 48 kHz while a second HD24 records and plays back 12 tracks of vocals and leads at 96 kHz, for a total of 36 tracks simultaneously.

Depending on the software version of your HD24, a warning message may appear or the sample rate indicator may flash indicating the mismatch in rates, but this will not affect operation.

Inputs and Outputs

The inputs and outputs of the HD24/EC-2are the same basic type as on a “stock” HD24: balanced 1/4” TRS jacks with a nominal +4 dBu level corresponding to–15dBFS on the HD24’s meter. In most installations, there will be no difference in meter readings or levels after you install theEC-2.

However, there is a slight difference in the balancing circuitry that may affect some installations. The EC-2features true differential inputs and outputs, with dual drivers on each output instead of the more common (and less expensive) “impedance balanced” (sometimes called “ground compensated”) method of balancing the outputs found on most audio gear (and on the original HD24 boards).

As a result, if you plug the output of the EC-2into an unbalanced input, the nominal output will be–2dBu, 6 dB less than if theEC-2was seeing a true balanced load. This is normal operation and has no effect on the final quality of the sound...it only reduces the readings on the console’s tape return meters. To avoid this 6 dB loss, simply plug the outputs of theHD24/EC-2into balanced inputs on the console.

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EC-296kHz A/D/D/A upgrade• appendix A

About the EC-2’saudio performance

An HD24 with the EC-2upgrade has audio performance far superior to that of any analog recorder, and a wider dynamic range than most input and output devices that may be connected to it. Here’s why:

The converter defines the sound

The first and last steps in digital recording—theconversion from analog to digital, then backagain—definethe audio quality of the digital recording process. Once captured in the digital domain as a series of ones and zeroes, the audio is protected for as long as the media lasts. So the converter you use when recording a master is one of the most important choices you can make in the studio.

The EC-2upgrade uses premium AKM 5393 analog-to-digital(A/D) and AKM 4393digital-to-analog(D/A) converters, among the best available today. The input and output electronics are virtually identical to those of the acclaimed Alesis MasterLinkHigh-ResolutionMaster Disk Recorder. Even at standard sample rates, the noise floor and distortion are lower than most units costing much more. The noise floor is 10 dB lower than a “stock” HD24, and 20 dB lower than standard Compact Discs and the original16-bitADAT. How much is 10 dB? From a laboratory standpoint, 20 dB stands for 100 times thepower—sothe dynamic range increase is analogous to the difference between a 10watt amplifier and a1000-wattamplifier. Because of the logarithmic nature of human hearing, to most people, each-10dB of difference sounds “half as loud”, so the noise floor of theEC-2will be perceived as 1/4th that of a standard CD.

The resulting 112 dB dynamic range is not only more than that found on a standard Compact Disc, it is much wider than the acoustic dynamic range of even the best recording studios. When you record analog audio directly into an ADAT HD24 upgraded with an EC-2,the recorder is literally no longer an issue in the overall sound quality. Even dedicated (and expensive!) outboard converters connected to the ADAT Optical ports of the HD24 have a tough time beating the specs of theEC-2.With proper recording techniques, any noise or hiss you hear is coming from theself-noiseof the microphones or preamps, not from the HD24.

When to use 88.2/96 kHz

Why 44.1/48 kHz?

Many engineers believe that the sampling rates that have been used up to now are less than ideal. The industry-standardsample rates were chosen at a time when digital storage was much more expensive than it is today. The “consumer” rate of 44.1 kHz was the lowest possible sampling rate that could still record and play back the highest frequencies in thecommonly-acceptedhuman hearing range of 20 Hz to 20,000 Hz. At a 44.1 kHz sampling rate, a 650 MB Compact Disc would be able to play back 72 minutes withoutinterruption—thelength of Beethoven’s Ninth Symphony.

In an era before digital mixing consoles and computer workstations, the 48 kHz sampling rate was designated the “professional” rate for two reasons:

1.the slightly higher sampling rate allowed more room for the antialiasing filter to do its work, and

2.professional recorders needed to be able to “pitch down” 12% and still play back the full 20 kHz frequency range.

The case for a higher sampling rate

While the traditional sampling rates give excellent performance (especially with today’s converter technology), there is criticism that these rates are too low to obtain truly audiophile quality. Most of this criticism centers on the filters that are necessary to make digital audio work.

Antialiasing filters

The Nyquist theorem, upon which digital audio recording is based, states that you can reliably record and play back any signal by sampling it at least two times the rate of the highest frequency you want to record. However, if there are any analog frequencies in the incoming signal that are higher than half the sampling rate, nasty-soundingreflections appear in the signal, known asaliases. For example, if a 47 kHz tone is sampled at 48 kHz, you’ll hear a 1 kHz tone, right in the midband of theaudio—hardlywhat you’d want to hear by getting “extended frequency response”.

So, early analog-to-digitalconverters had a steep “brick wall” analog filter on the input. To avoid

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