Cannot adjust volume with USB DAC

[jdforest]

I cannot adjust the volume via the webUI when I am using a USB DAC (Schiit Modi) as the output to my amplifier. This feature works fine when I output via the headphone jack.

I am pretty sure that volume control worked for me several versions ago, but has not in the last year. I seem to remember there was a conf file edit I needed to make, but I cannot find any reference to it.

Any suggestions?

Thanks.