Brent Jesse rebirth?

@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%. "