If memory serves, it was the same 7199 stage but with even an easier drive requirement. Again, purely from memory but if so, it was far more than adequate for the purpose.Busted.I played a little (too) fast and loose with my reply. Thanks for weighing in!
Upon reflection, I was probably thinking more about the "front end" of my own SCA-35 (Dynaco's little PP EL84 integrated), which is pretty rudimentary.
The st-35 stereo power amp is pretty terrific, yes. The SCA-35 integrated is nice, but kind of "value engineered" (which is not to say "muntzed").
Exactly. They used the "12AX7" half as the voltage amp instead of the pentode side of the 7199. Significantly lower gain, so that reduced the feedback.
Heavens, *four* jibes in the space of a few minutes? Alert the medics.
The SCA35 in my possession is a nice integrated but in my experience isn’t as clean and clear sounding as the PAS2/MKIV combo. I think the tone section is a little muddy. It acted mostly as a stand in when the main system was down, and also worked to power a pair of remote speakers.The st-35 stereo power amp is pretty terrific, yes. The SCA-35 integrated is nice, but kind of "value engineered" (which is not to say "muntzed").
My SCA-35 is fully functional (rehabbed) but is currently pulling time as a shelf queen -- as shown above.
I am a sucker for pp EL84 amplifiers.
PS My recollection is that microphonics can be a thing in the SCA-35 -- but I haven't had mine lit up (ahem fired up) for quite some time. I did source some pretty healthy 7199s for it from a regional source of some repute.
manual for the SCA-35 is available, e.g., at:
Speaking of value engineering: the application of PECs for the tone controls on the SCA-35 probably didn't help.
After 50+ years in this hobby, I do not find that lovers of valve amps believe they are magic at all, just different and it's a difference they happen to like. Suffering from a sensitivity to sibilance I find most solid state amplifiers more sibilant than good tube amplifiers with the right tubes. The problem with saying measurement can tell you if you will like the sound or not, is just not true. Measuring distortion at quantum above what a human can actually hear surely predicts very little.
Preference is fine - but tubes are a very expensive way to control things like sibilance. Which in many cases is a frequency response issue, easily (and much more cost effectively fixed) with DSP.
Although it is implicit in @egellings apt comments, a knock-on benefit of the simplicity and 'staging' of (most) vacuum tube audio amplifiers makes 'em easy to troubleshoot, too. That, and the ready availability of (most, many, or in some cases all) parts as new production* makes 'em about as future proof as any "technology" can be**.
Many things that nominally normal folks do all the time are extremely hazardous unless one is very careful. Driving an automobile fairly leaps to mind. 
We're kinda locked into driving automobiles in order to go anywhere, whereas tube amps are an optional hobby interest. I happen to enjoy my home brewed circlotron tube amps myself. They were fun to put together, and they reward me with music. How cool is that?Although it is implicit in @egellings apt comments, a knock-on benefit of the simplicity and 'staging' of (most) vacuum tube audio amplifiers makes 'em easy to troubleshoot, too. That, and the ready availability of (most, many, or in some cases all) parts as new production* makes 'em about as future proof as any "technology" can be**.
EDIT: Oh, that lethal voltages thing.
__________________
* E.g., the 2A3 direct heated (EDIT) high transconductance power triode, as far as I can tell, has been in continuous production (somewhere in the world) since RCA introduced the single-plate 2A3 in 1933.
** OK, mechanical clocks and watches, too -- I think the parallels 'twixt vacuum tube audio components and mechanical timepieces in terms of why they still exist and hold fascination for some folks are substantial & significant.
It feels good to build stuff that does something -- especially if it does that thing fairly well! was that humans tend to be almost amazingly poor at judging (relative) risks. This wisdom was imparted to me in a seminar by Bruce Ames (of "Ames Test" fame) in my grad school days. He was, at least as I remember the talk, kind of disgruntled by (or maybe about?) the mis-application of Ames Test data (which essentially used bacterial mutations as a screen for mutagenic compounds. The larger community (mis)took the Ames Test as a surrogate marker to predict carcinogenicity in humans, which kind of missed the point. A number of (probably) useful chemicals were thrown under the bus due to Ames Test positivity. 
simonpearce.com
Indeed, the guy who built our house had his office and shop a couple of doors down from Simon Pearce. Tropical Storm Irene totalled his offices, while leaving Simon Pearce mostly unscathed... but it looks like this year's tranche of heavy rains was tough on Simon Pearce in Queechee, too. 
