So, apologies, I meant to ask: Can you hear differences as the sample rate or bit depth changes?
I was just about to throw darts at it, but now it makes sense. I think it’s indeed possible to hear the difference in bit depth—especially with more complex passages like symphonic orchestras—because of the much higher dynamic range (around 146 dB for 24-bit compared to 98 dB for 16-bit).
As for sampling rate, yes, we can often perceive improved sound quality—typically a smoother top end or more natural transients—when we upsample or oversample the signal. This is mainly because upsampling shifts artifacts such as phase distortion and pre/post-ringing to higher frequencies, beyond the audible range. My Harmony Micro DAC offers both OS and NOS modes, and I did notice a slightly smoother, airier top end in OS mode, though with a bit of loss in detail. Personally, I prefer NOS mode.
As is known, upsampling can cause clipping, so I do reduce the overall signal gain a little. Roon converts everything to 64 bits before this so I can do this without further loss.
What you did (reducing the gain) is perfectly fine, but I just want to clarify that upsampling itself does not cause clipping. The 64-bit floating-point processing within Roon’s DSP engine, where upsampling occurs, provides virtually unlimited headroom, making clipping literally impossible at that stage. Clipping can only occur when Roon converts the signal back to fixed-point formats such as 16-bit or 24-bit PCM, as supported by your DAC. You can either apply a limiter to prevent this from happening or, as you did, reduce the gain to ensure that the converted signal never exceeds 0 dBFS.