I have an new install running. RPI 3B+ with the latest Volumio image. The system registers my DAC (Firestone Audio Fubar ) as a USB PnP Sound Device. The device works fine but the volume controls on the playback screen do not work.
Does your DAC have hardware volume control? If not, you will have to control at the amp or use the software mixer.
Yes the DAC has a hardware knob for the headphone out. It does not operate the DAC outputs. I found the setting and will investigate this further. Thanks for the response