OK thanks, it sounds pretty thin to me at the moment, I will try it again at 8 ohms, but I must say the 663 gets pretty hot even when run just as a preamp, whereas the xpa2 stays completely cool. I originally tested the 663 at 8 ohm setting but as I said it was a minimal fuse that blew not the amp that cut out, 2nd test was at 6 ohms but if it's distorting when volume is set a few dbls above zero wouldn't that be the same regardless of impedance setting? Guess I'm still confused.

"If you try to turn toward it, you go against it."