Topic: Optimal Volume Level with ADI-2 DAC

I am using the ADI-2 DAC to feed a single-ended tube amp (Unison Research Sinfonia). The input signals comes from Raspberry Pi (LMS/squezzelite) through SPDIF COAX.
By now I have followed the principle that volume should not be digitally reduced for all the discussed reasons ....
Therefore I am using an In-Line Attenuator at -24 db (www.funk-tonstudiotechnik.de/DKS-rt-sw-1.jpg) which allows me to put the volume knob on my amp between 9 and 10 o'clock.
Parameters of ADI-2 DAC are at:
HW Ref Lev = +7 dBu
Vol = 0 dB

Understanding the concept of Digital Volume Control I do understand that one paradigm might be over.
Actually, I put the knob of the amp to 1 pm and do all volume control through the DAC.
Practically, I am not hearing any difference.

Is this a reasonable approach? Should I contiune to use the attenuators?
What is the best rational for determing the "fixed" volume level of the amp?
Is there a lowest volume level for this DAC w/o loosing "data"?

Re: Optimal Volume Level with ADI-2 DAC

Take a look at this thread - it is very helpful.

https://forum.rme-audio.de/viewtopic.php?id=25399

Re: Optimal Volume Level with ADI-2 DAC

Sorry. I have already looked at the this thread but not finding the answers to my questions.

4 (edited by KaiS 2020-11-22 09:50:09)

Re: Optimal Volume Level with ADI-2 DAC

As almost all tube amps have a passive volume control immediately at the input, they do not work input level dependent.
This means, it doesn't matter if you use ADI-2's volume control or the one built in the tube amp - the "tube effect" result is the same, as both volume controls are located at virtually the same position in the signal chain.
To maximize ADI-2's dynamic range (S/N ratio) it's best to have its volume control set to 0 dB.

So:
• Set tube amp's volume control at middle position or some above.
• Switch Off ADI-2's "Auto Reference Level".
• Set ADI-2's volume control to 0 dB.
• Select the reference level that fits best to your loudness demands.
• Use the tube amp's volume dial to control the final loudness.
• Once you start to use any of ADI-2's DSP functions like e.g. the EQ, compensate possible level boosts with ADI-2's volume control until the Level Meter does not show overs.


If you want to use digital volume control, ADI-2 DAC has a clever option that increases the usable dynamic range by 18 dB: "Auto Reference Level".

So:
• Switch ON ADI-2's "Auto Reference Level".
• Set ADI-2 DAC's volume control to -18 dBr.
• Set tube amp's volume control slightly above your normal listening level.
• Use ADI-2's volume control to set the final listening level.

Now ADI-2 automatically selects the reference level that fits best to your loudness demands, while maximizing it's DAC's dynamic range.

Re: Optimal Volume Level with ADI-2 DAC

Thank you KaiS.

I tested both scenarios. Both work very fine and I cannot hear any difference as expected.
My preference is the option with using the digital volume control of the DAC as more handy due to several reasons.

I do have one further questions.
Why have you suggested to put the volume on -18dBr and not -12dBr, -6dBr or even at 0 dBr?

6 (edited by KaiS 2020-11-25 09:08:05)

Re: Optimal Volume Level with ADI-2 DAC

schiff1108 wrote:

Thank you KaiS.

I tested both scenarios. Both work very fine and I cannot hear any difference as expected.
My preference is the option with using the digital volume control of the DAC as more handy due to several reasons.

I do have one further questions.
Why have you suggested to put the volume on -18dBr and not -12dBr, -6dBr or even at 0 dBr?

dBr is the volume relative to ADI-2 DAC's (/ Pro's ) maximum possible volume setting, in case the post DA-Converter automatic analog level switching called "Auto Reference Level" is used.

This analog level switching has a range of 18 dB (ADI-2 DAC) or 20 dB (ADI-2 Pro XLR Out).


If you now start with -18 dBr (/-20 dbr) volume dial, the DA-Converter just reaches full scale level with a 0 dBFS music signal, hence maximum dynamic range.

This is favourable as base for the "normal" listening loudness.

Furthermore, a margin of about 18 dB should be enough to dial up, in case needed, for weeker sources or to listen louder.


Read manual page 37 (DAC) or page 49, middle (Pro) for further information.