Tubes vs Solid State - Imaging, Soundstaging, 3D

Assuming the noise floor is low and can't be heard anyhow, what is there to hear below it?

Al's comments above are the correct answer to this.

Chaos Theory points to the 'why' of it- the amplifier with feedback is operating in a chaotic fashion where the noise-distortion floor is much higher with a constantly changing non-repetitive signal.

Csontos makes a good point in his post above. IMO this has more to do with feedback and less to do with whether its tube or transistor in theory. In practice though it is much easier to build a zero feedback circuit using tubes than it is with transistors. Ninety-nine and 44/100% of all transistor amps run a considerable amount of feedback, hence the generalization.

For the time being designers have yet to universally recognize the importance of human hearing rules in audio design, so we are likely to see considerable differences in opinion for quite some time :)

In this conversation I've not discussed preamps although I have alluded to them by using the word 'circuit' as opposed to 'amplifier'. The same rules of human hearing of course apply to preamps, and you do deal with the same issues of feedback. However in preamps it is very easy to build a zero feedback circuit with vanishingly low distortion and wide bandwidth, so the argument in favor of feedback weakens considerably, especially in the face of the damage it can do (if you want to build the preamp with opamps though you are kind of stuck- that can only be done with feedback). If the preamp looses information, it really does not matter how good the amp or speakers are- you can't recover lost information downstream.

"For the time being designers have yet to universally recognize the importance of human hearing rules in audio design, so we are likely to see considerable differences in opinion for quite some time :) "

Few things are ever "universally" realized.

Does not make sense to me that such things would be ignored by the experts whose products can benefit.

More likely that different engineers make different judgements regarding what works best to meet specific product goals.

I'm a software engineer. Not much parallel I can think of where a long proven best practice is ignored these days by any good software engineer worth their salt.

Shigeki Yamamoto who is known for his line of SET amplifiers is very adamant about the adverse sonic repercussions of NFB. Even with his DAC design he eschewed OP- amps due to their copious levels of NFB and instead opted to build a discreet analog output circuit free of NFB same as his SET amplifiers. Another example of circuit and not limited to power amplifiers.

I'd like to hear from component designers/builders who believe in the advantages of NFB given its wide use and acceptance. I'm sure they feel ther are sonic benefits or they wouldn't use it. I wonder what's their opinion of the human hearing principle and if they accept the premise.
Charles,

I think the sonic benefits of NF is pretty well documented and understood as are the drawbacks (nothings perfect).

The fact that it is so widely applied would seem to speak for itself in terms of overall merit.

No NFB would seem to be the exception, not the rule. Those who buy into those benefits versus drawbacks have fewer options to choose from.

That's pretty much how these things work. Any product that is successful over time offers unique benefits.

One must also always keep in mind that there is a difference between theory and application. Theory is well, theoretical. Means nothing until realized in something in the real world you can touch , see, listen to, etc. That's what matters.

In my mind, the things that go into good sound are well documented and understood, especially by the "experts". Why re-hash here? Any assessment here is bound to be incomplete and flawed and affected by biases.

I've heard one of Ralph's amps at a show once with the big CAR speakers. It sounded very good. SO did other's at the show. Each had advantages/disadvantages beyond just sound quality. THings like cost, size, aesthetics, and other more subtle differences in features.

All that stuff matters. A lot of sound quality discussions are mostly about cutting hairs compared to the bigger things that the evidence clearly indicates matters to most.

Techno babbalo obfuscaturo a mundo. El tubo harmonico supremo.