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

Then why do almost all the damping factors measured by Streophile fall below 10

@dynamiclinearity I don't read Stereophile so I've no idea if this is actually true and if so, what amps to which you are referring.

It might be a better question to ask who the designer was and what was their intention. Did the designer have a degree? FWIW, most of the tube amps designed in the old days were designed by actual engineers. That's a lot less common these days. Not saying you need a degree to know what you're doing but it helps!

Some speakers, for example some open baffle designs, really don't do well if the amp has a high damping factor. Nelson Pass demonstrated this about 15 years ago a RMAF using a set of open baffle speakers and a solid state amp he built that was constant current rather than constant Voltage, so its damping factor was fractional since the amp's output impedance was about 50-60 Ohms. It sounded just fine and made good bass despite the small size of the OB speakers. 

So intention is a big variable here and Stereophile does not recognize that certain speakers need a higher output impedance from the amp to sound right. They just have their standard simulated speaker load and that's that.

Basil Poledouris’ incredibly dynamic score for Conan the barbarian.

Especially the opening track The Anvil Of Crom.

@prof I really like that LP. I think Poledouris did a great job on that.

Actually you don't need a degree to design tube amps. I winder if Bill Johnson had a degree. I'm lazy so I won't do the research but I'd bet a significant number of tube amps were designed by people who learned on the job. And I bet that includes a lot of well regarded tube amps. Most reviews for tube amps are positive.

Your example of open baffle speakers is a very small niche area and on top of that many open baffle speakers are designed to be used with higher damping factors.

I've used and loved tube amps. They have their pluses and minuses. In an imperfect universe like audio properly used they sound good. I'm just throwing out the idea for discussion that they may seem louder than a comparable solid state amp due to their high output impedance(low damping factor). I don't disapprove of tube amps.

When I bought some Alexia 1 a couple years ago, I took my Audio Research REF 75SE with me to pick up the speakers and to listen to them with my amp.  There was much written about those speakers being hard on amps due to the impedance dips.  That guy had a McIntosh MC452 so we compared his 450 solid states wpc to my 75 tube wpc.  We did not have to adjust the preamp volume...they had the same output volume and the REF 75 sounded better to both of us.  

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.