Geoff is correct. The Aleph current source varies. It is driven by a signal derived from the resistor network at the output. Yes, this can also be contrued as local feedback. He would prefer more global feedback, perhaps? The patent would be good light reading for your acquaintence.
Regarding feedback. I've got two pairs of Aleph 2s and a Mini-A (actually at the moment, it's a Mini-XA, but that's another topic entirely...) on hand to play with. In particular, I have tortured the Mini-A in ways that I wouldn't treat a 'normal' amp; since the parts cost is so low, if I blow something I won't shed any tears. Among other things I've tried: running the amp with the feedback loop disconnected entirely (open loop--something I normally only try with tube circuits) and various other ratios of closed loop feedback. Nary a problem. In fact the only thing that has given me a moment's trouble is the placement of the negative power lead from the power supply. For whatever reason, this can cause the circuit to get twitchy. I hooked a 1uF cap across the output and the amp didn't even notice. How much more capacitance the fellow might want to put on there, I don't know, but even the Mini-A can handle some capacitance. Note that this is something I wouldn't care to try with a lot of other solid state amps.
Granted, I usually think in terms of tubes, but I seem to recall seeing a number of schematics without Zobel networks. If the circuit can be contrived to be stable, there's no reason to put one in. It certainly isn't graven in stone that every amp shall have an output network. They interfere with the sound and are to be avoided if possible.
Grey
