Hmm. Maybe scratch what I said above.
I'd be interested in comments on the findings I report below. My techie knowledge is minimal and somewhat rusty. The sound differences I report are absolutely massive, the sort of difference your wife and auntie would notice, not subtle at all.
I was using an MC2 Audio MC1250 power amp that I was trying out. This is a massive 750wpc into 8 ohm beast. Driving Acoustic Energy AE1 speakers (200wpc, 88/89dB1w1m). The sound was near glorious. I've just swapped back to a Rotel RB991 power amp (200wpc) and need to crank the volume quite a bit more for the same level. I guess this makes sense as the amp is a quarter the size (12dB less) and the volume steps are 2dB for most of the gain range.
After only a few minutes listening the whole sound is hollow in a very strange way, body has disappeared and there's a hole in the middle of the stereo image effect. I had to check that I hadn't crossed the phase on one of the speakers and check all drive units were working, turn the DAC off and on a few times etc thinking there was a hardware fault. I'm familiar with the Rotel power amp and the fault is not there, it has a big full bodied sound generally. I've swapped back to the MC1250 and order is restored.
I think I might be suffering as I normalise FLAC and MP3 albums to 89dB so they won't clip on peaks. This is a fairly low average. Is this combined with the low output voltage on the Beresford DAC not providing enough input to the TVC for it's higher volume settings. Was I able to get away with it before due to the sheer power of the MC2 amp meaning I could use lower volume settings?
Well, I've just turned off normalisation. That should give me about 6dB extra into the DAC.