Kurzweil DMT interface User Manual

Introducing the DMT interface

The Kurzweil DMT interface (known henceforth as the
digital audio sample-rate and format convertor, which can synchronize the
sample-rate clocks of up to four independent stereo signals. It can work with
digital audio, bidirectionally, from Kurzweil K2500-series instruments, AES/
EBU sources, S/PDIF sources using either coaxial or optical cables, and
modular digital multitrack recorders such as the Alesis ADAT and TASCAM
DA-88. It makes working with multiple digital audio formats simple.

What’s In the Box

• The

• AC power cord

• 3-meter “KDS” interface cable for connecting the

You should save the

DMTi

longer KDS interface cable—15 meters—is available from Kurzweil.)

Why Do I Need It?

Anyone who has tried to combine multiple digital audio signals while keeping
them in the digital domain knows that this can be extremely difficult. Clicks,
dropouts, speed changes, and other anomalies show up with regularity, often
with no consistency, in the result.

itself

DMTi

) is a versatile

DMTi

with a K2500. (A

DMTi

’s packaging materials, in case you ever have to ship it.

The reason for this is that the AES/EBU digital audio standard (and its
offshoot, the “consumer” or S/PDIF standard) has no provisions for externally
clocking the samples—in other words, every digital audio signal carries its
own timing information. This means that two signals from two different
sources will have no common timing reference, so when you try to combine
them, errors will occur that cause samples to be skipped or dropped,
producing various unpleasant audible artifacts.

Since the modern audio studio uses digital audio from a variety of sources,
including hard-disk audio systems, samplers, signal processors, mixers, DAT,
CD, and digital multitrack tape decks, the problem has become acute. One
common solution has been to convert all of the signals to analog before mixing
them, and thus avoid the problem of conflicting sample rates altogether. While
this is acceptable in some situations, it obviously defeats at least some of the
purpose of using digital audio in the first place.

However, if the sample-rate clocks of these sources can be coordinated so that
they are in perfect synchronization with each other while staying in the digital
domain, these problems can be avoided without resorting to analog solutions.

1User’s Guide

What Else Do I Need?

To connect your
equipped with a KDS Output Option or KDFX Option. These options require
the K2500 to be running operating system version 2.3 or higher.

For hooking the
ate interface option installed into the
Kurzweil dealer if you have any questions.

What Does It Do?

The principle behind the
mented with some very sophisticated technology. There are four sets of digital
inputs, in three different formats, and four sets of digital outputs, also in three
formats. Each input and output comprises two channels of audio. The signal
on each input is converted, and then routed to any one (or more) of the out­puts.

The conversion process can change the sample-rate clock, either to a sample
rate determined by one of the other incoming audio signals; to the rate set by
incoming word clock; or to a rate set by the
sample-rate clock is chosen serves as the master for the entire unit—therefore,
all four of the digital signals appear at the outputs in perfect synchronization
with each other.

DMTi

to a K2500 Series instrument, the K2500 will have to be

DMTi

up to an ADAT or DA-88, you’ll also need the appropri-

DMTi

. Contact your Young Chang/

DMTi

is relatively simple, although it is being imple-

DMTi

’s internal clock. Whichever

The conversion process can also change the signal format, for example, from
AES/EBU to DA-88 (TDIF-1) or ADAT, or from the K2500’s proprietary “KDS”
format to S/PDIF, or from any supported format to any other. Although the
sample-rate clocks are all linked together, the format conversions of the various
audio streams can be independent of each other, and in fact multiple types of
format conversions can take place simultaneously.

The operation of the
functions, factory settings, or other obscure features to worry about. What you
see is what you get. However, the uses to which you can put the device are
quite varied—you might think of it as the “Swiss Army knife” of digital audio
tools.

2

DMTi

is very straightforward: there are no menus, hidden

DMTi

Inputs

KDS

Clock

Audio A, B, C, D

Modular Digital

Multitrack

Audio 1-2, 3-4, 5-6, 7-8

AES1

XLRoptical

Clock

Input

Select

Audio

KDS MDMAES1 AES2 KDS MDMAES1 AES2 KDS MDMAES1 AES2

Audio

AES2

Word Clock

In

Clock (derived)

Clock (derived)

44.1 kHz

Output Sync Clock

Select

Internal sample

rate generator

48 kHz

Outputs

KDS In
Return

Destination 1

ABCD

KDS Out

1-2 3-4 5-6 7-8

MDM

Destination 2 Destination 3 Destination 4

Output Format

Select (1)

XLRoptical

AES1

DMTi

AES3 AES4

AES2

signal flow

Output Format

Select (2-4)

Master Sample-rate Clock

Word

Clock Out

About This Manual

This manual starts with a description of all features and controls. After that,
we will discuss specific applications of the
the first two scenarios, even if they don’t apply to you: they will give you a
good overall idea of how to use the
easier to understand.

We don’t really expect you to read the entire manual through—each scenario is
meant to stand on its own. But besides the first two, it might be helpful to take
the time to read over all of the scenarios that might be of interest to you; the
more you understand about how the
able to form your own ideas about how to get the best out of it.

DMTi

in a variety of scenarios. Read

DMTi

, and will make the other scenarios

DMTi

can be used, the better you will be

3User’s Guide

AES/EBU inputs AES/EBU outputs

Input
Select

Optical In

S/PDIF
optical

In 1AES AES In 2 Out 1

Optical Out AES AESOut 2AES Out 3 Out 4AES Word Clock In

S/PDIF optical

output

input

sync

optical (audio)

ADAT

In

ADAT

Out

ADAT interface option

KDS (K2500)
input output
(& return)

In

KDS

OutKDS

Word
Clock

input output

AC power

Word Clock Out

Inputs

TDIF-1

In/Out

DMTi

rear panel

AES1 and AES2. These two AES/EBU inputs each accept a stereo signal.

These are the “professional” type of AES/EBU connectors, as described by
the AES Type 3 specification, which use XLR connectors. These inputs can
also accept “consumer” type AES/EBU or Sony/Philips Digital Interface
Format (S/PDIF) signals, but external adapters must be used. These
adapters are described on Page 10.

The AES1 input can alternatively be accessed with an optical connector, for

S/PDIF signals in that format. A switch on the rear panel determines which

AES1 input will be active.

KDS In. This is an input for the eight-channel digital output bus (known as the

“Kurzweil Digital Stream”) from a Kurzweil 2500-series instrument which
is equipped with a KDS digital input/output or KDFX digital effects
option. It uses a 15-pin connector and a 3-meter custom cable, included

DA-88 (TDIF-1) interface option

with the

DMTi

. (A 15-meter version of the cable is available from Kurzweil

dealers.) The sampling rate of the KDS bus is 48 kHz.

The KDS In also includes a two-channel output to the K2500, called the

“Return”, which allows signals being processed through the

DMTi

to be
sampled by the K2500, if the K2500 is equipped with the Sampling option.
(To use this feature, set the following parameters on the K2500’s Sample
Page: Input to “Digital” and Src to “Rtn”.)

4

DMTi

MDM. The

using either of two options:

The ADAT option, for use with Alesis, Fostex, and Panasonic decks, uses an

optical connnector for audio and a DB-9 connector for synchronization. The
pair labelled In is for signals from an ADAT. (Be careful not to connect the
ADAT option’s optical connectors with an AES or S/PDIF optical input or
output—you won’t damage anything, but the formats are not compatible.)

It is possible to use just the optical cable when connecting an ADAT to the

DMTi

potential synchronization problems, and it can’t do any harm. Some other
devices that use the ADAT interface, such as mixers, do not use the sync
cable.

The DA-88 (or “TDIF-1”) option, for use with TASCAM and Sony decks, uses

a single 25-pin connector which handles both input and output signals.

Word clock. This input accepts sample-rate or word clock from an external

source such as a digital audio system (with separate word clock signal) or a
synchronizer. The word clock signal is a square wave, with a frequency of
between 38 kHz and 53 kHz, at a nominal level of 5 volts peak-to-peak
(minimum 200 mV). The signal is carried on 75Ω unbalanced coaxial cable,
terminated with a BNC connector.

DMTi

can be interfaced with a Modular Digital Multitrack tape deck

, but it is not advised—using the sync cable is an easy way to avoid

Outputs

AES1, AES2, AES3, and AES4. These four outputs each carry a stereo signal.

Like the AES inputs, these are the “professional” type of AES/EBU
connectors, using XLR connectors, and they can also be used to drive
“Consumer”-type AES/EBU or Sony/Philips Digital Interface Format
(S/PDIF) inputs on other devices, with proper external adapters (see Page

10).

The AES1 output is also sent to an optical connector, for use with
compatible AES or S/PDIF devices.

Output switches on the front panel determine whether the output signals
are in “Pro” or “Consumer” format. The difference involves certain channel
status information. (There are also differences in level and impedance, but
this switch does not deal with them.) One switch controls output 1, while
the other controls outputs 2, 3, and 4.

5User’s Guide

KDS Out. This output is designed for linking two

the

DMTi

with other KDS-compatible equipment, including any K2500

DMTi

s together, or linking

Series instrument equipped with a KDFX board. Without the KDFX board,
those instruments have only a single return input pair, and that pair is
accessed, as described on Page 4, on the KDS In jack. The KDS Out jack,
unlike the KDS In, is unidirectional, and carries only the eight output
channels being generated by the

DMTi

.

KDS In. As described on Page 4, the KDS In includes a two-channel output to

the K2500, known as the “Return”, which allows signals being processed
through the

DMTi

to be sampled with the K2500.

MDM. If you have the ADAT option, a pair of jacks, one optical and one DB-9,

labelled Out serves as the output to an ADAT-format digital multitrack
recorder or mixer. (Do not confuse the ADAT optical connector with the
AES optical connectors.) On the DA-88 (TDIF-1) option, the DB-25
connector serves as both input and output.

Note: All of the audio outputs are in parallel, and all are “live” all the time.

Therefore, a signal that is r outed to the AES1 output will also appear at the
first two channels of the MDM output (“1-2”), the first pair of the KDS Out
jack (“A”), and the “return” to the K2500 located on the KDS In jack. You
can monitor signals as they go through the

DMTi

by listening to one of the

unused outputs through an appropriate device such as a DAT.

The Word Clock Output carries a word clock signal, the source of which is

determined by the Output Sync Clock Select switch. This signal is either
derived from an incoming digital audio signal; is generated by the

DMTi

is an echo of the signal appearing at the Word Clock Input. If the switch is
set to an input at which there is no signal, then either no signal or an
unstable, unpredictable signal will appear at this output. Like the input,
this output uses a 75Ω unbalanced coaxial cable with a BNC connector.

; or

6

DMTi

Source

outing

R

AES 1

AES 2

D

1-2

C

3-4

B
A

KDS MDM

AES 1, MDM 1-2, KDS A, KDS Rtn

5-6
7-8

Output Format

ower

P

Pro Cnsmr Pro Cnsmr

Destination 1 Destination 1 Destination 2

Source

AES 1
D

C

B
A

KDS

AES 2, MDM 3-4, KDS B

AES 2

1-2

3-4

5-6
7-8 A

MDM

Source

AES 1

AES 2

D

C

B

KDS

Destination 3 Destination 4 Destination 2-4

AES 1

1-2

D

3-4

C

5-6

B

7-8

A 7-8

MDM KDS

AES 4, MDM 7-8, KDS DAES 3, MDM 5-6, KDS C

Source

AES 2

1-2

3-4

5-6

MDM

Output Format

utput Sync Clock Select

O

AES 1
AES 2

MDM

KDS

WDCLK
Int 44.1K

Int 48K

DMT

igital

MDT

ulti-

interface

rack interface

Controls and switches

The Power switch has an integral green pilot light.

The Routing section consists of the four Destination knobs, which set up the
routing of the signals. Each knob is associated with a particular output pair—it
determines which input pair will be routed to the knob’s assigned output.

The first knob selects the input source for the first pair of outputs: AES1 (both
XLR and optical), MDM “1-2”, KDS Out “A”, and the “return” pair on the
KDS In. Since the various outputs are in parallel, the setting for this knob
affects all of its associated outputs simultaneously.

The second knob sets the input source for the second pair of outputs:

AES2, MDM “3-4”, and KDS “B”.

DMTi

front panel

The third knob sets the input source for the third pair of outputs:

AES3, MDM “5-6”, and KDS “C”.

The fourth knob sets the input source for the fourth pair of outputs:

AES4, MDM “7-8”, and KDS “D”.

The choices of inputs for all of the knobs are the same:

AES1
AES2
MDM “1-2”, “3-4”, “5-6”, and “7-8”
and KDS “A”, “B”, “C”, and “D”.

7User’s Guide

The Output Sync Clock Select control (which we’ll refer to as “Clock Se­lect”) determines the source of sample-rate synchronization for all of the

digital outputs. Whichever source is selected will be the master clock for all of
the signals at all of the outputs. You can select from one of the audio inputs
(AES1, AES2, MDM, or KDS), or the Word Clock (“WDCLK”) input, or you
can use the

DMTi

’s highly-stable internal (“Int”) clock source, which can oper-

ate at either 44.1K or 48K Hz. The setting of this switch is extremely impor­tant: if you select an input at which there is no signal present, the outputs will
produce unstable or unusable signals, or shut off completely.

There is a special way to use this switch when the

DMTi

is part of a system that

contains multiple ADAT-compatible tape decks. See Appendix A for details.

The Input Format switch on the rear panel determines which of the two AES1
inputs will be active: the XLR input or the optical input. The switch does not
change the signal format of the input: the XLR input can be used either with
“Professional” or “Consumer” (S/PDIF) sources, while the optical input
expects a “Consumer” signal.

The Output Format switches on the front panel determine whether the signals
leaving the AES/EBU outputs are in “Pro” or “Cnsmr” format. The difference
has to do with certain channel status information. One switch controls output
1 and the other controls outputs 2, 3, and 4. These switches do not turn on and
off the outputs: all outputs are always active. There are also differences in level
and impedance between the different digital formats, and it is possible that an
S/PDIF input could be damaged if it is fed with an AES/EBU signal. This
switch does not deal with those differences—use the attenuating adapter
described on Page 10 if this is an issue.

As a general rule, if the device you are sending audio to has an XLR digital
input, the corresponding Output Format switch should be set to “Pro”. If the
input is an optical or RCA connector, set the Output Format switch to
“Cnsmr”.

8

DMTi

Cables and adapters

KDS

The

DMTi

ships with a three-meter cable for connecting it to the Kurzweil

Digital Stream (KDS). This cable is used to link the
K2500-series instrument (equipped with the KDS or KDFX option), and/or to
link two
cable is available from your Kurzweil dealer.

MDM

An interface for a modular digital multitrack tape recorder is available as an
option for the
made by Alesis, Fostex, and Panasonic; and the other for use with
DA-88 (or “TDIF”) type decks made by TASCAM and Sony. Whichever option
you choose comes with connectors that are the same as on the deck itself, so
that connecting the
the tape deck. Consequently, the cable that is supplied with the deck for this
purpose can be used with the
optical connectors and two DB-9 sync connectors for ADATs. Note that
although an ADAT optical cable is physically the same as an AES or S/PDIF
optical cable, the two formats are not compatible: you won’t do any damage if
you connect one to the other, but you won’t get any signal.

DMTi

DMTi

with a Kurzweil

s together. It is a proprietary 15-pin format. A 15-meter KDS

DMTi

. There are two models: one for use with ADAT-type decks,

DMTi

to the deck is just like connecting a second deck to

DMTi

: a 25-pin connector for the DA-88, and two

sync

optical (audio)

ADAT

In

TDIF-1

ADAT

Out

In/Out

ADAT interface option

DA-88 (TDIF-1) interface option

S/PDIF

The AES/EBU inputs and outputs can be used with S/PDIF digital audio
signals (also known as “CP-340 Type II” and “AES Consumer” formats).
S/PDIF signals use single-conductor shielded video cable, terminated in RCA
(phono-type) jacks. (They can also use optical fibre cables.) There are
differences between AES/EBU and S/PDIF involving signal level, line
impedance, and channel status data. The circuits used at the
inputs are sensitive and tolerant enough to accept either kind of signal.

DMTi

’s digital

9User’s Guide

You can easily make an adaptor to bring S/PDIF signals into the

DMTi

’s AES/
EBU inputs. The shield of the RCA connector is wired to pins 1 and 3 of the
XLR connector, and the center (hot) conductor of the RCA connector is wired
to pin 2 of the XLR. Here’s a diagram of such an adaptor:

3

2

1

From S/PDIF Out

A similar adapter can be used to send AES/EBU signals from the

To AES In (solder side)

DMTi

to an

S/PDIF device:

3

1

From AES Out

(solder side)

2

To S/PDIF In

The signal at the AES/EBU outputs, however, is at the higher level required by
AES/EBU devices, and it is possible, although unlikely, that the input on an
S/PDIF device could be damaged if it is connected directly to one of these
outputs. An attenuating adapter can avoid this problem. If you are in doubt,
check with the manufacturer of the S/PDIF equipment to see if it can handle
the elevated signal level. To make an attenuating adapter, insert an 82.5Ω
resistor between pin 2 of the XLR connector and the center conductor of the
coaxial cable, and connect a 750Ω resistor from pin 3 of the XLR connector to
the center conductor of the coaxial cable:

1

From AES Out (solder side)

Generally speaking, when sending a digital audio signal to an S/PDIF device,
the Output Format switch for that signal should be set to “Cnsmr”. Also note
that S/PDIF signals sometimes have trouble travelling long distances. Using
high-quality video-compatible coaxial cable and making cable runs as short as
possible will keep problems to a minimum.

10

3

750Ω

82.5Ω

2

To S/PDIF In

DMTi

Using the

DMTi

: Scenarios

The next 22 pages will deal with specific scenarios for using the
tried to cover as many applications as possible, but you may find others.
Chances are, however, that you will find information relevant to your
application in one or more of the scenarios presented here. Please read the first
two scenarios even if their situation doesn’t apply to you: you will find them
useful in understanding how the

DMTi

works.

K2500 to Modular Digital Multitrack (DA-88/ADAT)

Application

This is one of the most useful applications of the
two to eight channels simultaneously from a Kurzweil K2500-series
instrument directly to a modular digital multitrack recorder (“MDM”) such as
an Alesis ADAT or TASCAM DA-88, without leaving the digital domain. The

DMTi

provides the proper signal conversions and also provides proper sync for

recording on the digital multitrack.

DMTi

DMTi

. We have

. You can record from

What you need

• The K2500 must be equipped with a KDS digital input/output or KDFX

digital effects option.

• The

DMTi

must have an ADAT or DA-88 (TDIF-1) option, depending on

which type of modular digital multitrack you are using.

Hookup

• Using the 3-meter KDS cable supplied with the

meter KDS cable), connect the KDS Output on the K2500 to the KDS input
on the

• Connect the modular digital multitrack to the

vided with the recorder for connecting two decks together. DA-88-format
decks use a single 25-pin “D” connector, while ADAT-format decks use one
optical and one sync cable for input and a similar pair for output.

• If you want to use an external source of word clock as the sync master,

connect that source to the

• You must use the multitrack recorder as the sync master if you are

overdubbing tracks (see next page).

DMTi

.

DMTi

’s Word Clock Input — however…

DMTi

(or the optional 15-

DMTi

using the cable(s) pro-

11User’s Guide

Settings

• Determine which MDM tracks you want to record to, and choose a source

pair from the K2500 for each pair of MDM tracks. Set the Destination knob
that is assigned to each output pair (going to the MDM) so that its input is
the desired pair coming from the KDS. For example, if you want to record
KDS pair A onto MDM tracks 1 and 2, set Destination 1 (which selects the
source for MDM tracks 1 and 2) to KDS A. If you want to record KDS pair B
onto MDM tracks 5 and 6, set Destination 3 (which selects the source for
MDM tracks 5 and 6) to KDS B. Set the other Destination knobs
accordingly.

• For your initial tracks, it is usually easiest to use the MDM as the sync

master: set Clock Select to MDM. You may, however, set it to KDS
(provided you are recording at 48 kHz—remember, the KDS bus always
runs at 48 kHz), or one of the Int settings. Alternatively, if you are using an
external clock master, you can set Clock Select to WDCLK. Note that any
time you are not using the MDM as the clock master, you must make sure
the multitrack tape deck is set to sync to an external clock signal.

When overdubbing to the MDM…

Modular Digital Multitrack decks cannot use different clock sources for
recording and playback at the same time. Therefore, if you are recording tracks
to a multitrack digital tape that already has one or more tracks recorded on it,
then the MDM must be the sync master: set Clock Select to MDM. There is an
exception to this rule: if you are using an external clock source, then both the

DMTi

and the MDM must be set up to slave to that source.

Special note for ADAT users:

If you are using multiple ADAT units, then one ADAT must act as sync master
for all of the others, as well as for any
decks. The sync signal is carried through the system on the Alesis Sync cable.
The

DMTi

can access that signal, provided a jumper on the ADAT option’s

circuit board is set correctly. See Appendix A for details.

DMTi

that is feeding signals to any of the

12

DMTi

KDS Out

KDS In

Knob

positions

choose

sources

Source: KDS A KDS C KDS B KDS D

Source

outing

R

AES 1

AES 2

D

1-2

C

3-4

B
A

KDS MDM

AES 1, MDM 1-2, KDS A, KDS Rtn

5-6
7-8

Output Format

ower

P

Pro Cnsmr Pro Cnsmr

Destination 1 Destination 1 Destination 2

Source

AES 1
D

C

B
A

KDS

AES 2, MDM 3-4, KDS B

AES 2

1-2

3-4

5-6
7-8 A

MDM

Source

AES 1

AES 2

D

1-2

3-4

C

5-6

B

7-8

KDS

MDM KDS

Destination 3 Destination 4 Destination 2-4

Destination: MDM 1-2 MDM 3-4 MDM 5-6 MDM 7-8

Knob

labels

show

destinations

to digital multitrack

DA-88: TDIF-1 I/O

ADAT: Digital In & Sync In

01:23:45:29

Source

AES 1
D

C

B
A 7-8

MDM

AES 4, MDM 7-8, KDS DAES 3, MDM 5-6, KDS C

Clock Select

must

be set to MDM

when overdubbing

utput Sync Clock Select

Output Format

O

AES 1
AES 2

MDM

KDS

AES 2

1-2

3-4

5-6

WDCLK
Int 44.1K

Int 48K

DMT

MDT

igital
ulti-

interface

rack interface

Output from DA-88 or
ADAT interface option

Variation: Sending to a DA-88- or ADAT-compatible mixer

The

DMTi

can be used to bring a K2500 signal directly into a digital mixer with
a DA-88- or ADAT-compatible input. The procedure is the same as when
working with a digital multitrack recorder. The mixer must be set up to sync to
external sample-rate clock.

13User’s Guide

Modular Digital Multitrack to K2500

Application

This is the reverse of the preceding scenario: you have a track on a modular
digital multitrack tape which you want to load (sample) into the K2500 for
manipulation and/or MIDI-triggered playback.

What you need

• The K2500 must be equipped with the Sampling option and either the KDS

digital input/output option or the KDFX digital effects option.

• The

Hookup

DMTi

must have an ADAT or DA-88 (TDIF-1) option, depending on

which type of modular digital multitrack you are using.

• Using the 3-meter KDS cable supplied with the

meter KDS cable), connect the KDS Output on the K2500 to the KDS input
on the
Return path—that’s what we’ll be using.)

• Connect the modular digital multitrack to the

vided with the recorder for connecting two decks together. DA-88-format
decks use a single 25-pin “D” connector, while ADAT-format decks use one
optical and one sync cable for input and a similar pair for output.

• If you want to use an external source of word clock as the sync master,

connect that source to the

DMTi

. (If this sounds backwards, remember the KDS interface has a

DMTi

’s Word Clock Input.

DMTi

(or the optional 15-

DMTi

using the cable(s) pro-

Settings

• Determine which pair of MDM tracks you want to sample. Select that pair

with the Destination 1 knob, by setting it to one of the MDM positions. The
Destination 1 knob routes the signal to the KDS Rtn bus.

• In most cases, Clock Select should be set to KDS. It can also be set to Int

48K or MDM, if the source tape was recorded at 48 kHz (the KDS bus runs
at 48 kHz). Alternatively, if you are using an external 48 kHz clock master,
you can set Clock Select to WDCLK.

• Set the following parameters on the K2500’s Sample Page: Input to “Digital”

and Src to “Rtn”.

Note: if you want to sample from the MDM at a rate other than 48 kHz, you
can go from one of the
See Page 22.

14

DMTi

’s AES/EBU outputs into the K2500’s digital input.

DMTi