Just wondering (I'm listening with a PC>>>DAC>>Amp>>>HP chain btw):

If you have a source and amp where you can both control the gain, what is generally the mix that produces the best sound?

Low-gain source >>> High-gain amp?

High-gain source >>> Low-gain amp?

Or is balanced the best way? Or is this one of those topics where it simply just depends and there is absolutely no general rule?

Anyway... I was listening for several days with the "low-gain-source-high-gain-amp" mix and I switched to the "high-gain-source-low-gain-amp" mix a couple of hours ago. Intriguingly, the latter sounds much better than the former, with the biggest improvement in terms of smoothness and clarity.

The only reason I could think of that could account for this is that maybe when the gain of the source is cranked up, there might be more/clearer data for the DAC to process, which might mean that a more refined signal is being passed to the amp?

Does that make any kind of sense whatsoever? Hehehe. That's just a blind guess.

stab in the dark:
high gain source and low gain amp will have a higher SNR

Assuming the source won't introduce distortion on high gain, I think it should have a better dynamic range which contributes to better SNR.

As said above, digital sources are at max. and adjust volume with you amp. Reducing digital volume (player adjustments) will loose bit length which are details and impact.

If you are sending out of your hp out, it might distort at max. so put your output at about 80% on a hp out and balance with the amp. You can fine tune your sound quality with the volume control of the hp out to get the most gain without distortion then amp control for loudness.