"tube watts" versus "solid state watts"

which is heavier a pound of nails or a pound of feathers? A watt is a watt no matter how you look at it. I would say what makes one amp sound more powerful has noting to do with wattage but frequency response.

My question is: is there any basis in electrical engineering for this effect? Can we say scientifically what's going on here?

Yes we can. There are probably several factors that are involved, but I believe that the most significant one is that solid state amplifiers clip more abruptly than tube amplifiers. So that if the power capability of the amplifier is momentarily exceeded by a small or perhaps moderate amount, the resulting distortion will be much more noticeable on a solid state amp.

Regards,
-- Al

Actually...a watt is current times voltage. It is unlikely that an amplifier will "run out" of voltage capability at the same time that it runs out of current capability. You could have an amplifier with low "rail" voltages that could deliver huge amperage at a low output voltage. This would, of course, be a waste because the amperage actually drawn is determined by the voltage and the impedance of the speaker. Similarly an amp might swing a high voltage into a light load, or for a brief time, but be limited in steady state performance by current delivery capability. Still, there are enough technical grounds to support an audiophile argument that a "tube watt" is better than a "SS watt". It doesn't take much technical ground to support an audiophile argument :-)