User's Manual

User’s Guide ADI-2 Pro FS – v 2.5

19.3 DSD Playback

During a DSD playback all DSP functions of all channels

are temporarily disabled, even when transmitting PCM. This

is signalled in several menus by brackets around the (ON).

Analyzer and level meter show DSD signals in blue color,

the current mode is therefore easy to recognize.

The change between PCM and DSD causes a low volume

click noise. For optimized sound and fidelity, the ADI-2 Pro

does not use any lossy analog volume control, hence can't

suppress the DAC's click noise.

You may notice clicks and cracks at the title change quite often with DSD, even when the next

title has the exact same sample rate. This is caused by the 1-bit format, which, unlike PCM,

requires absolute silence and DC freedom at the beginning and end of a title, so that the

transition as required by the 1-bit stream does not represent a random signal, which can sound

like a click or crack. Unfortunately, many freely available tracks are not 'clean' at the beginning

and the end. If these are played back one after the other by player software, the ADI-2 DAC's

level meters show that the noise to be heard does not originate from the ADI-2 DAC, but is

presented to the DAC as a signal to be played. The level meters are in the digital domain before

the DAC, so proof of a faulty input signal is easy.

Note

: A DSD playback via USB is only supported on playback channels 1/2. A DSD64 playback

in mode Multichannel via USB 3/4 does not activate the DSD mode.

19.4 DSD Record

The ADI-2 Pro converts the analog input data not only to PCM, but optionally also to DSD. Via

I/O - Analog Input - AD Conversion the AD-converter can be switched from PCM (Default) to

DSD. Based on the current mode the DSD data are then sent to the outputs AES and SPDIF

(DoP), USB (DoP via ASIO or ASIO native), and the analog outputs 1/2 and 3/4 (re-converted

by the DAC).

All modes, routings, source options and block diagrams of chapter 17 are valid for the DSD

operation as well, with both record and playback. The only difference: with DSD the circuit part

DSP is bypassed (no audio processing). In DSD mode all DSP functions of all channels are

temporarily disabled, even when transmitting PCM. This is signalled in several menus by brack-

ets around the (ON).

A mixed operation is possible. During a DSD recording, also AD conversion, a PCM file can be

played back and monitored via DA. Even a playback of DSD via channels 1/2 and simultaneous

monitoring of AES or Analog In via output 3/4 is possible, no matter whether the sources are

PCM or DSD.

Limitations exist, but they are identical with PCM and DSD. For example the limit of 192 kHz on

the digital I/Os AES and SPDIF means that in mode AD/DA only DSD64 can be used, not

DSD128 and DSD256. That's not different to PCM, where the higher sample rates 384 and 768

kHz can't be used. And the common clock does not allow any combination of modes. For ex-

ample a recording done at DSD64 (176.4 kHz) does not allow a simultaneous playback of 192

kHz; again the same limitation applies in PCM mode.