There is nothing obsolete or absurd about physical truth. Feedback was not solved…it’s not solvable as it is fundamentally flawed. Also, you cannot fix issues with 99% of amps, which are Class AB, with feedback because zero crossing distortion cannot be eliminated this way…only running in Class A works.
Do you read what you write? JFETS are more linear than tubes?
Points of correction: first, he said
some, not
all. So this is a strawman.
Feedback is known as 'control theory' in the rest of the electronics industry. It is
very well known, effective and not fundamentally flawed. There are several things that, if ignored by designers, will result in feedback sounding brighter and harsher. One is the practice of sending the feedback to a non-linear node where distortion is added to it as its being mixed with the audio. This causes it to do things its not supposed to, sort of like someone tugging on the steering wheel while you're trying to drive. The way feedback is applied in opamps solves this problem. If you treat an amp as a black box and run the feedback around it in the same manner you avoid this problem.
Another issue is that many amps with feedback (including tubes) lack the gain and bandwidth to support the feedback and gain (together known as loop gain) they have. When they run into the limit of the gain bandwidth product, the feedback decreases on a slope usually about 20dB/decade (6dB/octave). This causes distortion to rise 6dB per octave and can cause it to be unmasked. If you pay attention to this fact then the amp doesn't sound brighter with the feedback applied (this is because the distortion on that slope is perceived by the ear as brightness, since it tends to be higher ordered harmonics). This issue has been solved in a good number of modern amplifiers.
The class of operation is not relevant to zero crossing. We've had this go around before and yet you persist with this falsehood. If the designer is paying attention to the design, artifacts do not occur. OTOH even if the amp is class A, there can be problems- its all up to the design. ElectroVoice made some very interesting amplifiers in the 1950s that were push pull and biased so close to class B (which does not exist in real life, its either AB or C as class B is theoretical only) that they were able to get double the normal output power out of a pair of tubes. I recently restored one of these (A-20C). I put it on the analyzer recently and its residual distortion is a sine wave indicating a 2nd harmonic.
IOW your post above is entirely false.
The divide between SS sound and tube sound, particularly SETs, is as wide as it’s ever been.
Depends on who you talk to. We've had a number of customers dump their SETs in favor of our class D amps, not because they sounded like the SETs but with less hassle, but because they sounded
better (with less hassle).
The question you should ask is WHY don’t big, powerful SS amps sound good on those kinds of speakers that sound good with SETs or as you say SS amps that are closer in design to SETs?
The answer is that the speaker itself isn't designed for amps with a low output impedance.
The speaker is Power paradigm technology and the SS amp is Voltage technology. So they won't sound right when played together.
I had Martin-Logan loudspeakers for about 26 years. There was no solid-state amplification on Martin-Logan electrostatic panels that I did not find fatiguing and "dry."
We must have different definitions of the term "liquid."
That's what makes this a subjective and fascinating hobby!
FWIW ESLs don't behave according to the Voltage rules (described at the link above). For one thing, there's no box. They need an amp that does not double power as the load impedance is halved. Many SS amps make more and more power as the load impedance goes down, and ESLs typically have about 1/9th to 1/10th the impedance at 20KHz as they do at 50Hz or so. So a solid state amp will usually make way too much power in the highs and so will sound bright and because of this tilt to the highs, the ear will interpret that as 'dry'.
A Quad ESL is the benchmark when it comes to resolution and midrange anyway.
ESLs don't suffer thermal compression on account of no voice coil. They also don't suffer compression due to a weakening magnetic field on the voice coil gap on account of no magnetics. The only magnetic means to keep up with them is field coils. But to use them effectively, I think the ESLs (like the old Quads) must be a reasonable impedance such that they are easy to drive. The new Popori ESLs seem very promising as they not only benign load but also high efficiency. Their flagship has a 96dB sensitivity. As anyone working with panel speakers knows, you have to add about 6dB to that rating to know what they really are, since at one meter most of the sound of the speaker is not picked up by the microphone doing the measurement. That puts the flagship Popori at 102dB! We've been able to drive that one quite nicely with our little 5 Watt tube amplifier.
That's why my operating hypothesis is that the much higher gain of the new Incito S (Stavros predicted the high gain setting would be best) is somehow taking pressure off the Italians.
Its not. They have to make the same power regardless. A simpler explanation is the new preamp sounds better
I would be curious to determine a conclusively what was the source of the edginess.
It could easily be tubes. Microphonics in tubes can cause them to sound edgy.
You could try moving the tubes from the old preamp to the new one (if the same tube types are used) and then see what you think. If you don't do this then you're leaving a lot on the table in terms of finding out what happened, since tubes can have such a dramatic effect on the equipment in which they are used!