Firstable, I’d use a DragonFly (black one) DAC to connect to my amplifier (Denon UHC) without any trouble. (USB Rpi to Dragonfly, jack 3.5mm to RCA).
But I’d would like to connect my Rpi3 “Volumio” to my Sanskrit pro-B by the USB-B 2 port input.
And then…big parasite noise !!!
I’d change the usb cable, but no result.
Do I need change anything on Volumio settings (it recognize the sanskrit pro-B) ?
Other idea ?
Is the DAC working? I.e. is the audio output approx same as with your Dragonfly? Is it undistorted? You need to do some diagnosis
What is the nature of the USB noise? Broadband hiss or high frequency tones or low frequency mains hum?
Is the DAC OK when fed with Toslink signal from TV? This checks whether the DAC is OK.
Does the DAC (running Toslink) get noisy when connected to the USB of the RPI? This would suggest that the DAC is extremely susceptible to USB noise from the RPI.
Using the DAC on other USB ports on the RPI - do they all have the same issue?
Hum would suggest a ground loop problem or faulty RCA leads from the DAC to amp
So we have:
RPI driving Dragonfly USB DAC - works.
When the Sanskrit DAC is used it is powered by its own separate power supply not via the USB port in all cases? (The RPI might not be capable of supplying the necessary current if the power came via the USB port). Is the Sanskrit DAC powered before the RPI is powered? Not sure this matters since you say the Volumio software is recognising the DAC.
Mac driving Sanskrit DAC via USB - works. So the Sanskrit DAC is working via its USB. (What streaming software are you using on Mac?)
RPI driving Sanskrit DAC via USB port running Volumio (which version? Volumio would probably need this information to help) results in a complete malfunction. The DAC and the RPI aren’t communicating to each other correctly. USB cable isn’t the fault since swapping cables doesn’t fix the problem.
There seems to be some difference in the way the Mac and the RPI communicate to the Sanskrit DAC via USB. Unfortunately my experience is in hardware not software so I think we need another site visitor or the Volumio team to offer some advice here. Sorry I can’t offer more ideas right now