Is there any penalty I suffer, like in terms of reduced resolution of my digital music stream when I engage say -3dB or -6dB headroom?
Yes. Any digital volume control inherently attenuates, thus reduces maximum possible resolution of a digital signal. But as Roon DSP operates internally at 64 bit precision, then dithers down to the highest bit depth that your system supports, there is no effective loss of resolution for small to medium levels of headroom management or volume control attenuation. A -6 dB change is small. For a large change to reduce effective resolution, it would have to be on the order of -48 dB.
Thanks WiWavelength for that explanation
To my ears however, disengaging the DSP (via the master switch) sounds better to my ears than with any processing (headroom or upsampling).
Because of psychoacoustics, most people hear a reduction in volume – a quantitative change – as a decrease in sound quality – a qualitative change. That likely is what you are hearing.
Thanks. What you wrote sounds logical. So I listened with the headroom on and off and matched the output using a dB meter in each instance
somehow without the Headroom (or any part of the DSP for that matter) always sounds more clear (transparent) - anyway that’s my observations though you may well be technically correct.