Persistence of USB Audio Volume (with Workaround)

[Lolonois]

How to reproduce:

1. Configure USB audio, disabling audio jack (remove kernel module) does not make a difference (dtparam=audio=off in /boot/config.txt).
2. USB audio works.
3. In Emulationstation in Sound Config Menu, select "speaker" as output (NB: PCM and Master do no difference)
4. Raise Volume from 0 to 100
5. Leave Menu
6. Reenter Menu and see Volume set back to 0.

Expected:

• Volume set in dialog kept in the same way as with 3.5 audio jack output and change in volume does actually change the volume of the USB audio.
• Volume once set will survive reboot

Workaround:

1. Open retropie console
2. Check identifier of USB audio with amixer scontrols (mine is 'headphone')
3. sudo nano /etc/rc.local, add amixer sset 'Headphone' 100%. Adjust the percentage to your needs.
4. Reboot -or- repeat amixer sset ... command as pi user once and start in emulationstation.
5. Adjust volume with volume control of your audio amp.

Additional information:

• Make and brand of USB audio most likely does not have an impact (tested with three different brands and audiochips (C-Media, VIA and GeneralPlus)).
• Pi Model or other hardware: RPI 3B
• Power Supply used: Mean Well Switched Power Supply, up to 6A at 5V.
• RetroPie Version Used: retropie-4.4-rpi2_rpi3.img.gz from retropie website.
• Built From: Pre made SD Image on RetroPie website, updated with apt-get (now kernel: .4.14.79-v7+)