Volume control: pre DAC digital or post DAC analog?

[the chicks]

Current music playback system: Mac mini <USB cable> Dangerous Convert-2 D/A < balanced XLR cables> Pair of Geithain RL906 active studio monitors.

Currently controlling volume level in the digital domain using Tidal and iTunes apps respectively (after adjusting rear trim controls on each loudspeaker, using tiny screwdriver). D/A volume control is bypassed as it degrades the resolution way too much.

How much better sound quality do you think I might get by inserting an analog volume control between the D/A and the speakers and setting the volume levels in the streaming apps permanently to maximum? Naturally am hoping the answer is “None.”

 

[Kal Rubinson]

Currently controlling volume level in the digital domain using Tidal and iTunes apps

And do you know how these apps implement the VC?

D/A volume control is bypassed as it degrades the resolution way too much.

I am completely unfamiliar with your DAC but, again, the question is: How does it implement VC?

 

[kn0ppers]

I was going to link to the ESS Application Notes, but the website (at least for me in this moment) seems to be having some issues. Just some reading material.

 

[cyruz]

I always use a pre, set at the maximum comfortable level of listening, to avoid damaging my speakers. I was a programmer, I don't trust software.

Thanks to this forum I discovered the JDS Labs Atom. It's my inexpensive pre of choice in front of a TPA3251.

 

[MRC01]

The key metrics of a volume control are how much noise & channel imbalance it introduces. An analog volume control can be better, or worse, than digital. It all depends on how they're implemented. A good implementation of either should be transparent.

 

[bennetng]

I was going to link to the ESS Application Notes, but the website (at least for me in this moment) seems to be having some issues. Just some reading material.

The explanation in the pdf is poorly done though:
https://www.audiosciencereview.com/...depth-should-i-set-my-dac-to.8956/post-255104

For a computer-based system, it is a good idea to use two volume controls at the same time. One is on individual playback software, to maintain similar average level among different software. Another one is on the preamp, to set the global level. If there is no preamp, then use the one on the DAC. Instead of think about having two volume controls will further degrade the signal, one should realize that both digital and analog volume controls can exhibit issues when the level is too low. A digital volume control is ultimately limited by the DNR of the DAC, regardless of how high the digital precision is, an analog volume control may have channel balance issues in low volume as well.

 

[the chicks]

And do you know how these apps implement the VC?

I am completely unfamiliar with your DAC but, again, the question is: How does it implement VC?

Thanks very much for your quick response. Have emailed Tidal tech support asking how the app implements volume control - they have a backlog of enquires. Will post their response.
Not intending to ever use the DAC’S VC again - sorry should have stated that.

 

[FeddyLost]

From technical point of view most probably best solution might be some resistor-based stepped attenuator if your DAC have high output level. At least they are not very expensive and if properly done there's nothing to fail.

 

[deprogrammed]

I would hope a 2500 professional tool wouldn't degrade the sound . Could it be a setting or a malfunction?

 

[the chicks]

I would hope a 2500 professional tool wouldn't degrade the sound . Could it be a setting or a malfunction?

Good poinrt! However various other users of this model have also commented that they hear significantly better sound with the output trim bypassed. Never seen a comment the other way round. Incidentally left and right channels are not level matched and at very low settings the left channel cuts out completely - other users report the same with their own individual units. Never happens when controlling the volume using the on screen sliders in Tidal and iTunes when the DAC's attenuator is bypassed. It's for these reasons that I'm only seeking opinions relating to the signal paths described in the OP.

 

[JohnYang1997]

Noise performance with digital volume is limited by the DAC itself. And the SNR reduces as volume decreases.
Noise performance with analogue volume is limited by the volume control itself. It preserves SNR better as volume decreases.

But when DAC output has lower noise than a analogue volume controller, it's not the same answer anymore.

 

[trl]

How much better sound quality do you think I might get by inserting an analog volume control between the D/A and the speakers and setting the volume levels in the streaming apps permanently to maximum? Naturally am hoping the answer is “None.”

- 1) With cables disconnected, from 1m away from tweeters, in a quiet environment, check for the hiss/noise coming from your speakers.
- 2) Do the same, but with computer and cables connected to the speakers, but with no music playing.
Now compare the noise/hiss level between the two scenarios from above.

If scenario 2) has a more pronounced hiss, then probably the DAC itself might add some noise into your active speakers and an analogue control between the DAC-out and speakers input might help a bit by a small margin, although if it's a poor quality analogue control then channel imbalance might occur, especially when lowering the volume below "9 o'clock".

If hiss/background noise between the two scenarios is about the same, then worry not, because neither THD nor freq. response will not get altered by the software volume control described by you above.

I'm personally driving my active speakers from a Focusrite and I haven't noticed any added noise, but YMMV.

 

[the chicks]

- 1) With cables disconnected, from 1m away from tweeters, in a quiet environment, check for the hiss/noise coming from your speakers.
- 2) Do the same, but with computer and cables connected to the speakers, but with no music playing.
Now compare the noise/hiss level between the two scenarios from above.

If scenario 2) has a more pronounced hiss, then probably the DAC itself might add some noise into your active speakers and an analogue control between the DAC-out and speakers input might help a bit by a small margin, although if it's a poor quality analogue control then channel imbalance might occur, especially when lowering the volume below "9 o'clock".

If hiss/background noise between the two scenarios is about the same, then worry not, because neither THD nor freq. response will not get altered by the software volume control described by you above.

I'm personally driving my active speakers from a Focusrite and I haven't noticed any added noise, but YMMV.

Thanks so much.

Did the comparison:
Scenario 1 At 1m from tweeter could hear no hiss.
Scenario 2 At 1m from tweeter could hear no hiss.

Just for kicks tried the following:
Tried 0.3m from tweeter:
Scenario 1' At 0.3m from tweeter could hear no hiss.
Scenario 2' At 0.3m from tweeter could hear hiss.

Tried with ear almost touching metal grille in front of tweeter:
Scenario 1'' Ear almost touching grille could hear hiss.
Scenario 2'' Ear almost touching grille could hear much louder hiss.

Guessing the comparison at 1m likely means I'm good - I listen at a distance of 1.3m to 1.6m from each speaker.
Thanks again.

 

[the chicks]

And do you know how these apps implement the VC?

I am completely unfamiliar with your DAC but, again, the question is: How does it implement VC?

To quote from Tidal customer support officer's reply:
"The [Tidal app] volume level will not have an effect on the level of audio quality that you receive."

 

[trl]

They're defintely right, just a tiny little noise/hiss added by the DAC output stage, which shouldn't bother anyone if listening position is >0.5m.

 

[the chicks]

Thanks again tri - now have complete peace of mind. And thank you to everyone who responded.

 

[Kal Rubinson]

To quote from Tidal customer support officer's reply:
"The [Tidal app] volume level will not have an effect on the level of audio quality that you receive."

That's not a useful answer.

 

[ElNino]

I was going to link to the ESS Application Notes, but the website (at least for me in this moment) seems to be having some issues. Just some reading material.

This is really the most complete and accurate answer to your question.

 

[scott wurcer]

I have only one complaint about the ESS app note, it doesn't give any information as how to relate the -135dB noise floor to the noise of subsequent analog circuitry. From the plots virtually all DAC's have a flat ultimate noise floor at the output which is constant over frequency in the audio bandwidth. It would be nice to have all the information to state this as volts per root Hz so it can be compared to, for instance, a preamp after a passive resistive attenuator.

This all falls under the general topic of gain structure. Users of very high efficiency speakers often claim that some DAC's are noisy when they are actually just using the lower bits of the DAC to get a smaller signal. The MiniDsp folks have a note on this.

 

[kn0ppers]

Here is also the actual link to the ESS website. Maybe a moderator can replace the file in my first post with the link. I think I am partially to blame because I called it an App-Note when it really was just a presentation held at RMAF (Rocky Mountain Audio Fest) - the target audience is obviously not identical. Therefore I never held it to very high standards personally. That being said even some "real" app notes are questionable and one should always remain sceptical.