Please Read and express your feelings and opinions....

@kosst_amojan

Excellent points... I am learning amp design very slowly.  
My old buddy is designing a couple of Pure Class A amps now,  and he is no different.... He actually forms complete circuit layout in his head before he lays it down on paper... Then he builds, then he listens, then he changes, then he listens. When he gets it right, he'll etch his own boards. These days he is convinced that micro circuitry will sound best. 
Unfortunate for me,  this is over my head.  I can follow a schematic, but I don't have the knowledge to lay one out. The most that I can do is to make a few parts changes when finished understanding that one cap or resistor sounds differently than another.  

My opinion on the "failings" of yester-decade's gear is if those characteristics were desirable, why isn't anybody listening to wax cylinders on hand cranked phonographs? After all, the motorized, tube amplified, voice coil driven sound of the 30's was an evolution of that.

While that is true, its a simple fact that no-one is listening to 30's technology around here. The list of improvements is much to long to list here- and I'm sure you are aware of them.

...The hardest thing I've had to do is learn to listen for what distortion is. That has brought me into strong agreement with the belief that dynamics are closely associated with distortion.

+1

IMO/IME, about 95% of the time when audiophiles use the word 'dynamics' they are really talking about distortion and that word can be safely substituted into the conversation without changing its meaning.

The reason this is so is because the ear uses the higher ordered harmonics to sense sound pressure (GE demonstrated this in the 1960s but little was done with that research). This is probably due to the fact that pure sine wave tones don't exist in nature.

Its right at this point that our philosophies about how to get good sound probably differ; I am of the opinion that since our ears are so sensitive to these harmonics that its not a good idea to do anything design-wise to generate them and so specifically avoid doing that in our designs. This means that I don't use feedback because feedback, while suppressing distortion, also adds some of its own, and all of higher ordered harmonics which can be easily heard.  So if I can do a design that does not make those harmonics, it will be smoother and not sound 'loud'.

I've been accused of using 'antiquated' technology in this regard and that is true, but SITs were a short-lived technology in the 1970s and there were no small signal and driver devices that were SITs- only outputs. Regular transistors just don't have the linearity **and** soft clipping to do the job. That is why tubes are still around BTW; if really inferior (and not just antiquated) they would have been gone long ago.

@atmasphere 
"Each 2150 uses global feedback (proudly: its manufacturer suggests that manufacturers who don't use feedback simply don't know how to do so properly)" About the Boulder 2150 from Stereophile. Different strokes for different folks. 

I've heard noise about SITs coming back a bit on account of them being more efficient at converting and inverting AC and DC back and forth. Who knows. 

"Each 2150 uses global feedback (proudly: its manufacturer suggests that manufacturers who don't use feedback simply don't know how to do so properly)" About the Boulder 2150 from Stereophile. Different strokes for different folks.

That isn't quite true- but it is true that many who **do** use it aren't administering it correctly. The problem (known since the 1950s- see Norman Crowhurst) is that feedback makes distortion of its own thru bifurcation of the signal- and so adds higher ordered harmonics and intermodulations interpreted by the ear as brightness and harshness. And no-one has sorted out yet how to get an amplifier to clip graciously while using it. Here is an excellent article regarding the application of feedback and its pitfalls, several of which don't get addressed in many modern designs (and its not an 'anti-feedback' article):

http://www.normankoren.com/Audio/FeedbackFidelity.html

I recommend reading all parts.

I've got a SIT amplifier right now (and not just a Sony VFET either). It is one of the best solid state amps I've heard. Its too bad this technology got binned before it really was understood.