USB Volume (vs. S/PDIF & Toslink)

Even after reading a few similar posts I’m a little confused about why I can only use DSP volume control (vs. Device Volume) when using a USB input. Is it something to do with the USB standard? Are there any workarounds that would allow me to use Device Volume (i.e. control volume from Roon control).

Right now my Roon endpoint is an RPI running RoPieee. If I get an audio HAT with a Toslink or S/PDIF output will that get me back to being able to use Device Volume? (I’m assuming so, but want to be certain).

Not sure what forum policy is on this but I’m bumping this ‘cause I’m really hoping for a response!

Device audio means that you have a preamplifier that enables it’s native (digital or analog) volume control to be manipulated via a USB connection. This does not involve the actual digital audio bitstream at all. Mytek’s have this ability for example. It is a control function.

DSP volume is entirely different, where attentuation is applied over the actual digital stream.

A spdif HAT like the hifiberry or allo will not leverage device volume.

If your question stems from concern over bit truncation via DSP volume, I wouldn’t worry about it. Roon DSP volume is very well implemented.

Actually, volume is not a part of any audio protocol standards, not SPDIF over coax, not Toslink, and not actually USB either.

Some vendors have implemented volume control over USB and Roon takes advantage of that, but it is not standard.

As Rob said, DSP volume works fine.

Thank you both. Interestingly Device Volume works fine with my 7 Sonos endpoints. But this helped me to understand that getting a HAT for my RPI and connecting over TOSLINK or Coax isn’t going to get Device Volume to work with my RPI w/ RoPieee. I’ll live with DSP volume control as you suggest.