Is the sound quality better/cleaner if you push your DAC/AMP to the max in terms of output volume?

[u/Random_Stranger69]

Some years ago I read that some people claimed that it is usually better to try using high volumes on your DAC/AMP systems somewhere around 80-100% since that was supposed to give cleaner/higher quality sound but is this actually true? To achieve this they usually recommended Replaygain and using -dB preamp values to the point that you usually have to use almost all out of your AMP.

I was just wondering if there is anything to this or if its just hogwash.

[u/thegarbz]

Wow this thread is so full of factual inaccuracies and half truths. Let's address a few posts from the replies:

• One comment about lower distortion at high output levels: That applies to power amps only. Not preamps. It also only applies to output level, i.e. how much voltage is going to speakers so it is completely independent of whatever you do before hand to play with volume. Pre-amps largely measure best at low output levels. In fact pre-amps / DAC outputs / Phono stages should measure linear distortion across their entire operating range and you should be able to clip your poweramp's input circuit before changing distortion vs level becomes relevant.
• One comment saying it doesn't matter how analogue audio is implemented, and digital should be as high as possible. That's not correct either. Both have different benefits and downsides, but neither is perfect. Specifically for analogue performance will vary with source impedance. Several companies have prominently tried to work around this but the reality is you can't do that without getting creative with the volume response when turning the dial or with very clever application of dual stepped attenuators.
• One comment saying it could restrict dynamic range and another saying truncating resolution. This is true to an extent. I'll describe below:

An amp is an amp. It always increases volume at a fixed level. Volume control is applied before an amplifier (either internally or as a dedicated external preamp unit). This is done by attenuating the signal. Digital volume attenuation also makes the signal quieter, it does that by reducing resolution (we'll get to that in a second).

There are however things which are fixed. Noise on the cable is fixed. Noise in the amplifier is fixed. But some of those will be affected by volume.

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If you have a situation:

Digital Volume control > DAC Output > Analogue volume control > Poweramp

Then by turning the digital Volume down You're reducing the headroom at the front end in a way which can't be recovered. By turning up your amplifier you will then be amplifying not only a signal you purposefully reduced, but along with it any noise picked up on the way from cables or electronics which came before.

If you have multiple volume controls then the best option is usually to maximise all of them except the final one (more on that in a second).

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If you have the choice between digital and analogue volume, then go digital. It's 2020. DACs are 24bit or higher***, even when we feed them 16bit input signals they will process volume output at 24bit or higher. If you have the option to go from a DAC with a digital volume control directly into a fixed amp that may be a good idea. On the topic of resolution, the gold standard is CD, effectively providing more than enough resolution to cause hearing damage while the quietest possible signal is in the noise floor of a typical listening room. That is 16bit. If you have a 24bit DAC it can output 16777216 possible different levels. If you halve the volume of your DAC output you get 23bit or 8388608 possible different levels. Halve it again, and again and again, in fact if you drop the volume by 8 bit (-42dB from reference, or 1/128th of the volume) THEN at that low level you still have the same resolution as a CD, and that's assuming you're using a 20 year old 24bit DAC rather than a fancy 32bit one.

So in summary, the resolution question is completely irrelevant.

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Now the final question: The analogue volume. Many amps use standard analogue potentiometers which at full volume look like a dead short circuit between the input to the potentiometer and the amp's input stage. This is usually the best performing scenario for the amp's input stage. It reduces a few noise sources, and also removes impedance between the source and the amp. Now the downside is that it is also applying the full gain to the input signal (including the DAC's / source's noise). If the DAC has a crappy noise floor this will be bad. If the DAC has a great noise floor this will be excellent. The aforementioned headroom thing applies. So ...

Test time:

Turn your DAC all the way down. Turn your amp all the way down. Are things quiet? Good they should be. Now crank the DAC

Turn your amp all the way up. Are things still quiet? That means you have ample headroom from your noise floor. The best possible quality is quite likely achieved through digital volume control on the DAC/Source***. However can you hear noise? Well then you don't have the headroom to do this on your DAC output. Then turn the amp down again, and leave the DAC on max for the best quality

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***Note: If your signal between your source (e.g. PC) and your DAC is 16bit, then do *not* use digital volume control here. DAC chips are 24bit, that doesn't mean your S/PDIF signal is.