Thanks. I'm also a physicist (well, engineering physics actually). REW gives not just THD but also the odd and even harmonics. But I still can't see what makes the tube amp sound better after this measurement (btw its Mastersound not Masterworks, from Italy). The measured distortion also includes the speakers.
Tube vs Solid State Amp measured with REW
I have both a tube amp (Masterworks SET 300b) and a solid state amp (Arcam A32), with Klipsch Forte 4 speakers. The Masterworks sounds much better; more clear, very lifelike. But when I measure with REW the frequency response and THD are about the same (albeit with some variations over the range). Is there any other parameter that causes one amp to sound better than the other, that doesn't show up on the measurements?