Digital volume control vs analog volume control

[restorer-john]

Wouldn't you prefer a single knob that magically adjusted all the different stages optimally for the desired level?

Once set, I only use one knob.

Seriously, the goal is the lowest residual noise at the end of the chain, and at the same time, allowing the level I need. In reality, it hardly varies- much. Preamp gain and power amp attenuation are the balancing act to get the lowest noise and maximum DR.

My power amps are in the 120dB+ S/N, so the limiting factor is usually the gain stage in front. And I like preamps, so 90dB+ S/N is the bottleneck with most of them in real terms.

At this time of the year, it doesn't matter. The airconditioning to keep me cool shaves off 40-50dB at least, so it's all academic.

 

[Willem]

Wouldn't you prefer a single knob that magically adjusted all the different stages optimally for the desired level?

This is precisely what the RME ADI-2 offers.

 

[stephc_int13]

I think we should make the distinction between volume control done at the software level (multiplying each PCM sample by a value between 0 and 1.0f), fully analog volume control done by a good old potentiometer, a digitally controlled volume input fed to the DAC chip and a digitally controlled analogue volume circuit (or chip).

I am going to investigate further but I recently noticed that my system seems to sound better (I know it could be placebo) when the volume control on Windows and on the playback software are at 100% and both the preamp and the amp are in the low tier volume.

Several effects could be at play here.

I don't know how Windows handle volume control internally, but I won't be surprised if it was all software, meaning very small loss until the signal is converted to PCM before being assembled as packets being sent over USB.

As far as I know, the data has to be converted to something like 16bit/44Khz up to 24Bits/192Khz or something. My source is Flac 16Bits/44Khz and I don't use any advanced drivers.

If the packets are sent as 16bits/44 it means that at 50% volume it is effectively sent as 15bits. No big deal, except when you play at very low volume like 4-5%. at this level the range loss might be noticeable, not sure.

Other effect is that amplifiers tend to have lower distortion at low volume.

If anyone investigated this, I'd be happy to read your findings.

 

[boxerfan88]

I have both. Digital has rounding errors. Analog has issues with resistance strip/wiper. Honestly neither would make a significant difference.

My main rig is using digital volume control.

 

[kongwee]

As far as I know in DAC, digital or analogue volume control doesn't make a difference in data being fed.. The volume will not touch the full blown data spending into DAC. As far as I know digital control is controlling the power rail of the DAC ship. Analogue is additional opsamp or discreet circuit to control volume after the DAC output. You will lose resolution in bits when you control in computing environment like using gain control in EQ for example.

 

[MaxwellsEq]

I am going to investigate further but I recently noticed that my system seems to sound better (I know it could be placebo) when the volume control on Windows and on the playback software are at 100% and both the preamp and the amp are in the low tier volume.

.....

If anyone investigated this, I'd be happy to read your findings.

This is the thread for you. It will keep you busy! https://www.audiosciencereview.com/...nding-the-windows-audio-quality-debate.19438/

 

[MattHooper]

On the other hand, digital attenuation usually reduces the (relative) distortion. If your goal is to maximise THD+N of the whole system, a combination of digital and analogue attenuation is likely to give the best result.

I figure, at least in terms of my digital source, I'm doing pretty well with a Benchmark DAC2 fed into a Benchmark LA4 pre-amp for attenuation.

 

[Newman]

Variable analogue output coupled to a properly dithered digital attenuator, just be aware when you attenuate digitally you turn down the signal not the noise whereas analogue attenuates both.
Keith

That’s a very loose statement, Keith.

If the noise is in the program, D and A both attenuate it.

If the noise is in the power amp, D and A both don’t attenuate it.

If the noise is in the preamp’s analogue circuitry, D doesn’t attenuate it, and A only attenuates noise in that part of the circuit which is upstream of the volume control, and does not attenuate noise in the analog circuitry downstream of the volume control. Since it would be poor design to put the analog volume control right at the output terminals, one would expect some analog circuitry downstream of the volume control, which the volume control will not attenuate.

Plus, analogue IC type volume controls introduce their own noise and distortion.

cheers