Control volume with DAC or power amp?

[olds1959special]

I'm using an SMSL DL200 DAC going to an SMSL PA200 power amp, which can work as a power amp or integrated. I believe the sound is better when I set the PA200 to pure stereo mode, bypassing the volume control, then using the DAC to control the volume, vs playing the DAC at full volume and controlling the volume with the amp. Does that make sense or am I just hearing things? The input sensitivity of the PA200 when in integrated mode is unclear, so maybe there is distortion that way?

 

[staticV3]

Does that make sense or am I just hearing things?

Only measurements would tell.

Everything else is speculation.

 

[DVDdoug]

The "theory" of "gain staging" says to keep a strong signal (for the best signal-to-noise ratio) and attenuate at the last possibility. That way, the noise generated along the way gets attenuated along with the signal, except for any noise generated in the power amp itself.

Sometimes analog potentiometers don't "track" well at low volumes (the left & right go out of balance). That doesn't happen with digital controls.

Often power amps don't have a volume control and when there is one, it's usually intended as a "gain control" to be set and the left-alone. Sometimes they'll have separate left & right gain controls so they are not practical for everyday volume control.


Sometimes one volume control is more convenient than another, especially if you have a remote control for one and not the other.

So... If you don't hear noise in the background, use whatever is most convenient.

 

[theREALdotnet]

I believe the sound is better when I set the PA200 to pure stereo mode, bypassing the volume control, then using the DAC to control the volume, vs playing the DAC at full volume and controlling the volume with the amp. Does that make sense or am I just hearing things? The input sensitivity of the PA200 when in integrated mode is unclear, so maybe there is distortion that way?

When feeding an unattenuated digital signal to the DAC there is a risk of inter-sample overs and clipping, depending on how close the signal gets to 0dBFS. If digital attenuation is applied before oversampling and conversion, this risk is mitigated (assuming the attenuation is always at least -3dB).

Only measurements would tell.

Yes. Whether or not inter-sample overs are the issue you're having can only be confirmed by measurements. DeltaWave analysis of the DAC output of a full-scale versus an attenuated signal could show this, for example.

The input sensitivity of the PA200 when in integrated mode is unclear, so maybe there is distortion that way?

I think it's unlikely that the full-scale DAC output would overdrive the input stage (before volume control) of the amp and cause distortion. Again, measurements would provide clarity.

 

[TurtlePaul]

I like to use the DAC for volume control. Most power amps or integrated amps use multi-gang pots which have channel balance issues that pulls the center image to the left or right when adjusting the volume. Most DAC have perfect digital volume control.

 

[olds1959special]

I like to use the DAC for volume control. Most power amps or integrated amps use multi-gang pots which have channel balance issues that pulls the center image to the left or right when adjusting the volume. Most DAC have perfect digital volume control.

The PA200 has a digital volume control.

 

[staticV3]

The PA200 has a digital volume control.

Close but not quite: the PA200 uses a TI PGA2311 for volume control, which is a digitally controlled analog attenuator using a resistor ladder network.

In theory, this combines the best attributes of digital and analog attenuation into one.

 

[olds1959special]

Close but not quite: the PA200 uses a TI PGA2311 for volume control, which is a digitally controlled analog attenuator using a resistor ladder network.

In theory, this combines the best attributes of digital and analog attenuation into one.

So then bypassing the analog attenuator by using the amp in pure stereo mode should yield an improvement, especially if I listen with the DAC set at higher levels, right?

 

[Chrispy]

More of a how would we know what you prefer thing....go with what you think sounds best.

 

[TurtlePaul]

So then bypassing the analog attenuator by using the amp in pure stereo mode should yield an improvement, especially if I listen with the DAC set at higher levels, right?

The specs of that chip are in line with some of the best audio opamps. If well implemented you should never be able to hear it (other than the volume reduction).

 

[olds1959special]

Since I like the idea of full quality at lower volumes, I went back to using the volume control of the amp.

 

[Chrispy]

Since I like the idea of full quality at lower volumes, I went back to using the volume control of the amp.

Possibly/probably just more the idea than the reality.....

 

[AnalogSteph]

I would use a combined approach, setting the amplifier volume as high as you would ever need and then using the DAC for day to day changes. (When using normalization with levels being similar across all major playback applications, DAC volume should normally be at maybe -26 to -30 dB.) This way, you should have plenty of dynamic range without an acute risk of blowing out your speakers in case of accidents.

Ironically, the DAC probably sports higher dynamic range than the power amp's analog volume control. If the DL200 is not prone to volume oopsies, you may want to use the PA200's passthrough mode (AMP MODE = PURE AMP STEREO). It's probably moot if you can't hear any hiss either way though.