Brent Jesse rebirth?

@hilde45  I'm sure your right. My earlier experiance was with class AB. Nothing wrong with those but I learned that I have a taste for that 2nd harmonic distortion or whatever it is that tubes and, apparently, SITs have. I have come to accept that hifi is the skillful creation of a desirable audio illusion and we get to choose what elements we want in our illusion. I also buy into Nelson Pass's zen proposition that less can be more, so simplicity appeals. In that respect class AB is usually quite a bit more complex circuit wise so maybe a bit more distant from the music. Class D contradicts this, it would appear and I have to admit I had a Rogue Sphinx and now have a ClassDAudio Gan amp. The Rogue, of course has tubes in the preamp section and Hypex in the back so it's no surprise that it appeals to folks like me. But the Gan fet amp Really has that same sweetness that I like, though it leans more to a "clean" sound. I think Ralph is talking mainly about Gan fet amps when he boosts Class D.

@bruce19 

I hear you about tubes and SITs having a distinctive second harmonic character, but that character isn't entirely absent from Class AB. Pass XA-25 is Class AB and there are others that produce second harmonic distortion too. It may come down to degree and consistency. As I understand it, in Class AB, odd-order harmonics tend to creep in more as the amp moves through its crossover region. Very design-dependent.

On simplicity, the Sphinx is actually a pretty complex design: tube mu-follower preamp, Hypex Class D output stage, discrete MOSFET headphone amp, and a MM/MC phono stage all in one chassis. Three different technologies interacting. That's not a knock against it but it's not simple.

@hilde45...pretty sure the XA-25 is Class A, not A/B?

https://www.passlabs.com/products/xa25/

@mofimadness Right. My mistake.

I was confusing it with other Pass units and also the exceptional ability of the XA-25 to go well beyond 25wpc.

Atkinson:

"Pass Labs specifies the XA25's output power as 25Wpc into 8 ohms and 50Wpc into 4 ohms (both equivalent to 14dBW). However, as you can see in figs. 4 and 5, the amplifier exceeded its specified power output at the clipping point, which we define as when the THD+noise equals 1%. At that THD+N percentage the XA25 delivered 80Wpc into 8 ohms (19dBW) and 130Wpc into 4 ohms (18.1dBW). It appears from the shape of the traces in these graphs that Pass specifies the XA25's power as when the THD+N is close to 0.01%. "