I would sincerely suggest to the OP to listen to an example of a modern high negative feedback solid state amplifier as described above and compare its sound quality to the Renaissance 70/70 and be your own judge. I’m not convinced that the "modern " high feedback would be superior sounding.
Emphasis added
I completely agree with this advice, although not his conclusion :)
IME the distortion spectra (the distortion signature) has to be right; too many designers ignore this simple fact.
Most speakers today are designed assuming that the amplifier is able to behave as a voltage source (meaning it can make the same voltage output regardless of load). Some speakers in high end audio are not designed for this behavior- and for those few, sometimes an amp with a high output impedance will sound better.
some modern super low distortion amps can produce a somewhat harmonically lean, clean-white, antiseptic kind of sound that may be not be favored by listeners used to a more saturated, rich, bloomy type of sound that some tube amps deliver...
Once any frequency response issues are sorted, the differences we hear between amps is the distortion signature. You can think of any amp as having a perfect amplifying aspect and also a distortion aspect thru which the signal travels. That distortion aspect is the 'sonic signature' of the amplifier. SETs have a pronounced 2nd and 3rd harmonic, which masks the higher orders (SETs actually have more higher ordered harmonics than any other kind of amp, but when masked you don't hear them), giving them a lush, smooth sound. Some amps which do not have such pronounced 2nd and 3rd have unmasked higher orders, which contribute to the description in the quote above.
That's not just a subjective thing; these aspects are easily measured; and if the proper distortion spectra results in the amplifier design, no matter if solid state or tube, the amp will be easy to listen to, involving and relaxed. So an SET might have the right distortion signature, but imagine two or three orders of magnitude less. you'd hear more detail with no downside (no brightness or harshness).
I know how hard it can be to understand that this is so- for the last 70 years we've simply had to listen to know if an amplifier was going to be musical and satisfying in our systems. That's a lot to overcome! But also for most of that time, building an amp with enough GBP wasn't possible, and the industry really didn't want the market to know that. Heck, that wasn't too hard to sweep under the carpet because of how hard it is to explain what gain bandwidth product even is!
