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"tube watts" versus "solid state watts"

I'm sure you, like me, have seen it written more than once that brand X tube amplifier, rated at 30WPC, sounded more powerful / more authoritative than brand Y solid state amplifier, also rated at 30WPC. Or that brand Z tube amp, only rated at 15W, was comfortably able to drive brand A speakers, because those 15 were tube watts and therefore up to the job. Heck, I think I've even heard the phenomenon with my own ears.

My question is: is there any basis in electrical engineering for this effect? Can we say scientifically what's going on here?
128x128twoleftears
eldartford
4,262 posts
 
Unsound...How about a Hybrid?
fpeel
455 posts
 
Wouldn't that be a hermaphrodite?
unsound
7,333 posts
 
Would that be AC/DC ?
audiofeil
4,011 posts
 
>>Tubes are men. Transistors are women.<<

Everybody chant with me:

ohhmmmmmmmmmm............
atmasphere's avatar
atmasphere
11,959 posts
 
So if its not clear- the difference in tube and transistor watts has to do with distortion- generally speaking tubes have more distortion, but most of that is lower order which the human ear/brain system does not care about. Transistors tend to have more higher ordered odd harmonics, and while in only trace amounts (100ths of a percent) these are the harmonics that the ear/brain system used to detect loudness, so the human ear is very sensitive to them.

The result is that a tube amp may have a higher percentage of usable power, even though it has less overall power.

In the case of clipping, a tube amp will seem to compress dynamics slightly before audible clipping occurs. With transistors the clipping characteristic is very audible and instantaneous. This is why guitar players, who overdrive their amps on a routine basis, prefer tube amps. In fact, it is the guitar amplifier business that drives tube availability, not high end audio!
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