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Pass Labs A/B amps vs Class A amp and Actual Power

Dumb question; how can you compare the actual power or ability of an amp to drive a tough load (such as a Magnepan) when looking at a Pass Labs A/B design such as the X250.5 or X350.5 vs one of the full class A amps like the XA60.5 and XA100.5? For example, which amps would (from a standpoint of just pure power/grunt) drive 3.6's better, an X350.5 or a XA60.5?
stickman451
unsound
7,329 posts
 
Stickman, many if not most amps that are touted as doubling down Class A amps actually halve their Class A out-put as they do so. Including Nelson Pass' previous Threshold designs:
http://www.stereophile.com/solidpoweramps/1290thresh/index1.html
stickman451 OP
553 posts
 
For me it's probably a mute point; the XA100.5 is most likely more than I can/would spend even at used prices...
unsound
7,329 posts
 
All the more reason to make sure your buying what your expecting. Mind you, the same might be true re: doubling down power/halving Class A bias for the amount of Class A bias in the Class A/AB amps.
rtn1
535 posts
 
Let's be clear. The XA.5 doubles its Class A power. The XA100.5 would provide 200 beautiful class A watts before going class AB. This is indicated in the specs on the Pass website. The older XA series kept the output fixed at lower impedences.
stickman451 OP
553 posts
 
Rtn1, that is exactly what Pass told me today. All of the XA.5 amps will double their Class A output into 4 ohms.

Guys, any thoughts on the absolute minimum room width for Magnepan 20.1's?
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