Pass Labs:What to expect fm XA60.5 to XA100.5

"Are the 3.7s fused?" Yes, 5 amp mid and 2 1/2 ribbon.
I really want to try the XA100.5s on my 3.7s, seems like a great match.

Light:
'More power means more complex circuit' is not necessarily true for Pass amps.
I've seen an amp on his DIY site, which you can adjust output power of simply by continuing to parallel output devices. Of course, some additional changes need be made, perhaps a higher VA rating on the main transformer and a higher current bias power supply. More devices DOES mean an additional opportunity for component failure, but SS devices ran within normal parameters have a very high MTBF. I'd bet as much as 20 Pesos that the higher power amp is at least 98% as rellable as the lower powered version....other things being equal.

I heard it said that the XA30.5 and the X150.5 are the SAME amp, save for some bias circuitry adjustments. I'm not sure, but it is feasible, I suppose. Though, if it were ME making these amps, I'd have an A-A/B switch so you could CHOOSE the mode which suited you or your mood.

Good news about the 3.7s and fuses. Ribbon fuse veterans of Magnepan refer to the Ribbon as the 'fuse protector'. Pretty fragile when presented with hi current distortion. Depending on the low / mid crossover point, the entire panel may be capable of sinking 12 amps...perhaps 50% more than the 1.6 with which I'm most familiar. My ancient MG-1 fuse was a paltry 1.5 amps above an unknown crossover. Based on the current capability and advertised sensitivity, even with all the stuff I said.....above.....I'd never try the 30.5, but go to at least the 100.5s......

Has anyone tried either the XA60.5 or the XA100.5 with the Vandersteen 5A? I'm wondering if either Pass amp has enough power for medium sized room and moderate listening levels (@10 ft).

Nicks,

I use a pair of XA-100.5s with my Vandy 5As in a 14 by 24ft room. The meters on the XA-100.5s rarely move (leaving class A) unless I am playing fairly loud (above average 90dB) or listening to something with quite a bit of dynamic range (symphonic music) -- in either case on peaks above 98-100dB. My listening position is about 12-14 feet back from the plane of the speaker baffles.

I originally purchased a pair of XA-60.5s for my system after running a pair of ModWright KWA-150s in bridged mode on high bias. I really liked the tone of the ModWrights and thought I'd like to try full class A. Given that the 5As have powered woofers, I thought that the XA-60.5s would be sufficient for my system, room, and listening habits, but I found them swinging out of class A (moving meters) more than I liked. So I traded up to a pair of XA-100.5s and have been very, very happy. That said, if I find myself with extra cash lying around after upgrading my front end and preamp, I would love to have a pair of XA-160.5s just because.

Based on my experience, I think the XA-100.5s would be more than adequate in your situation.

I have thiel 2.4 speakers. I am curious as to how you compared the modwright amps to the pass xa100.5. I very much appreciate your input.

Tom