Volume control works fine on D10 with Volumio when mixer type is set to hardware. My question was actually how XU208 does the volume control? Is it using the 32 bit arithmetics in a same way 32 bit DACs do when doing volume control, as it is described in the document below?
http://www.esstech.com/files/3014/4095/4308/digital-vs-analog-volume-control.pdf
XU208 does the volume control for sure --- the exposed control in /proc/asound/ are hardware controls, and OS does nothing except passes the raw values in.
However it does not indicate hardware does that correctly. the firmware is free to do a SInt 16 * SInt 16 / VOL_MAX-> SInt 16 calculation internally rather than a (SInt 16 pad 16bit 0s) * SInt 16 / VOL_MAX -> SInt 32 for redbook
Topping may only modify the reference firmware implementation slightly, and the reference firmware implementation may do it correctly, so there're chance it works according to the doc you linked here.
But we don't have the firmware code, so I can't really make any conclusion.
The most straightforward way to see how it works is to ask @amirm to do a performance benchmark
Last edited: