Tam - It would be interesting to have the amp tested to see what the distortion level is at a particular frequency and also at a particular output level.
Total harmonic distortion is measured in relative decibels, then converted to a percentage.
1% THD is actually measured at -40 dB. A 100 dB fundamental will have a 60 dB of total Harmonic Distortion - probably not audible to most people, but possibly adding a bit of warmth.
A highly regarded tube amp from Manley was rated at 40 WPC with a THD of 1%. When measured by Bascom King, it hit over 10% THD at 38 watts. This is now a -20 dB level. Most Tube amps have "almost all" of the THD in the second harmonic.
For example, in the case of the Manley amp, at volume, a 100 dB, 100 Hz tone will have an 80 dB tone at 200 Hz. It won't sound distorted in a "bad" way, but rather will be warm.
A tube amp and SS amp "should" sound identical, unless one is either adding distortion or has a fairly wide response curve.
It is usually the Tube amp with the wider response curve, which again lead us to that warm sound.
I would wager a lot of money that people who love the tube sound would have a much harder time identifying the tube sound under blind tests.
It's a great conversation to be had at an event like a "home theater meet".
To your specific amp, based on what you posted about your experience with it, it seems to have a pretty linear response curve and lower distortion.
And yes, looking at the tubes is going to add to the experience. They just look awesome!
