Why do tube amps often subjectively sound more powerful than SS ?

So when I got the Bryston amplifier, I thought, since it was more powerful, put on really powerful music that will take advantage of it like the Conan soundtrack.

 

I put in the Bryston, cranked it up and…huh? Where was that power?

Why did it actually sound thinner?

Less impactful?

Man, I love that soundtrack. And film.
Yeah, another way I can put my experience with various amps - push pull tube amps tend to sound "good to the last drop". I listen loud and I’ve pushed hard on some vintage PP tube amps in the 20 - 35 Watts / ch range. Until you hit hard clipping, they sound amazing (euphonic) all the way through. Sweet, fat tone.

With solid-state there’s more of a phenomenon like: when you crank it up, you start hearing stuff presented in a way that makes you want to back down the volume again. This can occur even when theres’ still AMPLE power reserves left before approaching hard clipping limits. With tubes, you may keep wanting to crank it up until you actually hit hard clipping.

Probably due to a combination various factors - like harmonic distortion spectrum (which Ralph has educated many of us on), and possibly some dynamic compression with tubes (as another poster mentioned) that can actually work toward the presentation’s favor in some instances. "Loudness wars" with regards to digital mastering gave dynamic compression a bad name, but it’s not all bad.

@mulveling 

yes, that’s been exactly my experience!

I have sensitive ears, And I have always found that my tube amplifiers give a sense of ease and relaxation, So that I can crank the sound much higher and still enjoy it.  Whereas when I have a solid-state amp, I find myself turning the volume down.

tube amps typically have much higher current which is more important than watts in several ways (but marketing won't tell you this).

It’s because they’re old school sound, from the days when tubes were all there was.  Some of us were born in the days when SS didn’t sound so good. SS has gotten much better. But then again, so have tubes. Today’s tube amps aren’t your Great-Grandfather’s tube amps. 

Actually you don't need a degree to design tube amps.

@dynamiclinearity That is certainly true. But it helps, especially if the amp in question has a feedback loop. Designing a good feedback loop is a bit less trivial if you want to get it right.

My point was there's been a resurgence of SETs since the early 1990s, most of which don't use feedback. They tend to have a high output impedance and so speakers that expect the amp to behave like a Voltage source (which is most speakers made) don't work right with them. Hence along with SETs we have more horn and open baffle designs meant to work with low power tube amps with high output impedance.

If Stereophile was measuring such an amp it wouldn't measure well by their standards but might sound pretty decent.

Some tube amps I would expect to have a higher damping factor are those made by Roger Modjesky.

Futterman made some OTLs with quite high feedback and had damping factors as high as 40:1. You can put more feedback on an OTL since you don't have the poles created by the output transformer; you can have a greater phase margin. Khron Hite made some laboratory amps (UA-101) in the early 1960s that had as much as 80dB of feedback (and hence had very sophisticated feedback design) which had a damping factor of 100:1.