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

In terms of the more power means more complex circuit with more stuff going on, so less good sound, that was certainly born our with the original Pass Amps, where the Aleph 3 was considered the best sounding, although very low on watts.

I'm going to be moving from an Aleph 5 to XA60.5 (I think) soon - I have Maggie 3.6s, so very hard to drive and damping factor means a lot in my case. I'm tempted to actively bi-amp and use Spectral or NuForce on low end. (Crossover is 225 Hz on Maggie 3.6), that is the only reason I'm not sure if I'm getting the XA60.5s. So, even if I'm still underpowered, it should be a massive difference from the Aleph 5, the XA60.5s have sooo many more Volts and Amps.

Overall I think I agree that a smaller Amp - *if* you have met your dynamic requirement - will sound better. In my case Maggie 3.6s seem to take any amount of power and still want more, so I am considering X350.5s too, and that might actually sound better in my case. Really take control of the bass panel...

Okay - this is my main comment. Add a Supratek or Joule-Electra pre-amp. With the rest of your system as it is, you'll be shocked by what happens! And then you will really have a system that plays with the big-boys :). I think it will be completely different than what you hear now.

Light,
Maggies are generally not a bad load for a good amp like Pass. IF the new 3.7s follow Magnepan pattern, there should be NO impedance dips to weird lows OR any huge phase angle stuff to deal with.
OTOH, they ARE fairly low sensitivity which is made up for by being dipole. Damping factor? Anything over maybe 20 will be fine. Even low damping tube amps work well, if enough power. The air damps the mylar pretty well, and being a single sided driver, not as coupled to the magnets as a good cone driver. The push/pull 20.1 may be slightly different.
You are right about dynamics and power, though...

Power users of panels like some of the big 'd' offerings. Spectron? massive.

Also, if Pass amps thru the line are anything like the XA 30.5, while it is 30x2 into 8, pure class 'a', the redline is almost 200x2into 4 in a/b. If the XA 60 does the same thing, it should be quite sufficient. Whoever said to look at the meter had it right. If the bias stays in 'a', or just a flicker periodically or on crescendos, than that is probably enough juice.

Given my listening habits (important for all to consider) I'd probably be quite happy with the XA30.5 level amp. The 60? WOW! OR if I had really deep pockets, a pair of 30s, as biamp!

Are the 3.7s fused? My 1.6s have a 4amp mid/tweet. I doubt the whole panel draws 8 amps at the limit. Thats just over 250 watts RMS..... How would that work out for dynamic power? Lots, I suspect.

Yeah - Spectron - that is what I meant when I said Spectral :).

"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......