Question re: volume control and bit-perfect playback

[kapusta]

I am still a bit confused about the different volume control options (Software, Hardware, Disable) in regards to bit perfect playback. Something is not adding up for me in the actual execution.

I am using a RPi3 with an Allo Boss DAC, running version: 0.4b (build: 20170229)

My question is regarding the "disable" function.

My understanding is that "disable" bypasses both the hardware and software volume controls.
My understanding is that the purpose of this is to ensure bit perfect playback, because the software and hardware controls alter the digital info (no longer bit-perfect).

However, what I have found is that while the "Disable" option does in fact override the software volume control, it does NOT override the Hardware Volume Control - it simply locks it at whatever it was last set at (even though the volume control knob on the Playback screen indicates otherwise)

For example:
I start with Software and Hardware volumes set to 100, and Volume Control set to "Disable", and my amp set for a normal listening volume.

Then....

-I set Volume Control to "Hardware enabled" (and save setting)
-I on the Playback screen, I set the volume to 75 (which is very quiet, barely audible)

-I then change Volume Control to "Disable" (and save setting)
-I would expect that volume would then increased to the previously "Disabled" volume.... but it does not.
-The music is still at the same level (barely audible), even though the volume knob on the playback screen says 100, which should be MUCH louder.

Restarting the system does not make a difference.

So it would seem that the "Disable" option is NOT bypassing the Hardware volume control, but simply locking it in place. It would be like instead of bypassing a volume control it is just pulling the knob of so you can't turn it.

So if this is the case, what hardware volume is "bit-perfect"?

If it helps, this is the debug code taken from the above scenario:
---Volume Control Disabled,
---Software Volume last set to 100,
---Hardware Volume last set to 75,
---Playback volume is disabled and reads 100
---Actual volume output is same as last Hardware setting (75).

Code: Select all

https://pastebin.com/DNM1WmsU

Thanks,
Kapusts

[hondagx35]

Hi Kapusts,

your findings are correct.

Disabled means that volume can't be changed is set to the last level.
We decided to implement it in this way do not kill your loudspeakers while setting volume to disabled.

Setting hardware volume to 100% and then disable it should give you a bitperfect config.

Frank

[cmh714]

Yes for bit perfect the Volume needs to be disabled.

To increase your volume since it sort of sounds like its low (and I had this issue initially), look into alsamixer settings.

You can get there via your web browser: Your_IP:8080 should work. You can also ssh into the Pi and do it as well.

GL.

[hondagx35]

Hi,

Yes for bit perfect the Volume needs to be disabled.

That is not correct. 100% Hardware volume is also bit perfect.

Frank

[kapusta]

Hi,

Yes for bit perfect the Volume needs to be disabled.

That is not correct. 100% Hardware volume is also bit perfect.

Frank

If that is the case, is there any reason not to just enable Hardware Volume and leave it at 100% rather than disabling it? It would be convenient for the times when I need to turn it down but don't feel like getting up and going over to the stereo receiver (Convenient, but certainly not critical).

Thanks

[hondagx35]

Hi,

If that is the case, is there any reason not to just enable Hardware Volume and leave it at 100% rather than disabling it?

Maybe someone knows better, but i would say there is no reason for not doing it like this.

Frank

[kapusta]

To increase your volume since it sort of sounds like its low (and I had this issue initially), look into alsamixer settings.

You can get there via your web browser: Your_IP:8080 should work. You can also ssh into the Pi and do it as well.

GL.

Thanks for the info.

Actually, I don’t have any problems with the output being too low. If anything I would not mind it a tad lower.

The output volume of this (at 100%) is much louder than any other standard hifi component I have (CD player, phono, BT receiver, tape deck). Its a bit louder than the headphone jack on my iPhone turned up to max volume. It does not seem to be distorting/overdriving anything, so I guess it is is OK.