Hi Alan,
I’m of course no expert on these matters, but my reading suggests that using the digital volume control on my intended Gustard X26 III DAC, driving a P282 directly, would reduce bit depth by truncating digital data, especially at lower volumes, thus degrading resolution, dynamic range, and low-level detail. Is this not the case?
Cheers,
Ash
Hi
@Ash
There is a bit of a misunderstanding generally about how digital volume controls work. I cant comment specifically on the Gustard as I dont know how its implemented, but here is a general comment.
The calculations for a digital volume control should be performed at higher bit depth than the actual recording you are playing, so 32 or 64 bit. I use Roon software and it uses 64 bits.
Doing this means that no resolution is lost. For info 16 bit has 65535 signal levels, 24 bit has 16,777,215 levels, 32 bit has 2,147,483,647 levels and 64 bit has 9,223,372,036,854,775,807 levels.
Also it should be noted that real world recordings simply dont acheive 24 bit resolution (SNR). 18 to 19 bit is about the best you will find.
Also that real world noise levels in the best electronics (dacs, surrounding amp circuitry etc) only reaches about 22/23 bit.
So "resolution" is a non issue with digital volume.
A real theoretical disadvantage of digital volume is as follows.
All electronics have a level of noise. A DAC will produce a certain level. When using a "perfect" analogue volume pot, when you turn it down both the music signal level *and* the inherent background noise of the source will turn down also. As such in theory it will maintain the signal to noise ratio.
Using a digital volume, when you turn it down the music signal level decreases but the inherent source background noise remains the same. As such signal to noise ratio decreases.
So that's a real theoretical disadvantage. Now let's step back into the real world.
Source electronics noise levels are now so low that this potential disadvantage is irrelevant. DACs are around 130dB SNR. The noise is completely inaudible and then some.
Analogue volume controls aren't perfect. They will *always* be noisier. They will have issues such as balance tracking (although much better with stepped ladder).
Power amplifiers will be the noisiest part of any signal chain as they have a lot of gain to raise the source signal to levels able to drive speakers. The power amp will be the limiting factor in most systems.
So, all the concerns about digital volume controls are moot in a real world system. If properly implemented they will always perform better than an analogue control.
The only reason to have a pre amp is if you have multiple sources (dac, streamer, turntable etc) and need to switch between them. Otherwise a DAC/streamer run directly into a power amp will perform better.
Just an aside, when recording and mixing music these days in the studio, A DAW (digital audio workstation) is usually used. The mixing volume level changes for each instrument is done with 64 bit digital volume control.
In conclusion, dont be concerned in any way about digital volume control. I would always use it in preference to analogue.
Hope that helps