Problems with DSD: Mac Mini & Benchmark HGC2

I have Roon up and working on my Mac Mini (10.12.3) connected via USB to my Benchmark GGC2 DAC. Mostly I am thrilled. Nearly all my frustrations with iTunes have now vanished.

My library is nearly all AIFF, most standard resolution, some HD files. I thought I’d try out my DAC’s DSD capabilities, so I bought an DSD64 album from HDtracks.

I’m using DSP Volume, so I figured I’d have to set it at 100% for the bits to come through okay. But the DAC did not sense a DSD file (at any volume setting). When I set the volume to Fixed Volume, the file played properly.

Then I set the volume to Use Device Controls (though I do not believe the Benchmark responds to USB commands to adjust its volume–certainly the knob on the front panel doesn’t respond, and there is no mention of it in the manual). In this mode, when I set the volume to 100%, the DAC senses a DSD file and plays properly. And when the volume is set at less than 100%, the DAC goes silent. And in this mode, when playing an AIFF file, the volume functions like it should.

So what’s going on? In particular, is Roon doing the volume adjustments properly (because I doubt the DAC is doing anything), i.e., is the PCM properly dithered when Use Device Controls is selected? And why isn’t DSP Volume behaving like this (which is what I expected)?

Thanks for any pointers.


This sounds right – you’ll need fixed volume on in order for Roon to communicate to the DAC properly. We can’t make changes to the signal path on the fly, based on where the volume slider is at any given moment.