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New Pass Labs X.5 series versus previous X series

Pass Labs is in the process of re-dedesigning their entire X series into the new X.5 series. As of this writing X150.5, X250.5 and possibly X350.5 are already shipping. The X600.5 are expected to start shipping early in the new year. This thread is to discuss experiences with the new amps, their sound signature, perceivable improvements over the old series, and of course dissenting opinions. Everyone's perspective is welcome--X and X.5 owners, X.5 window shoppers, Dealers, and all other audiogoners with a passion for affect by the bug of audiophilia.
guidocorona
jameswei
795 posts
 
Do we know what is changed in the circuitry?

I can GUESS that X.5 series should have a sound somewhere between the X series and the Aleph series, actually probably between the X series and the XA series. Somewhat smoother and more liquid than the X series, but not as much so as the XA's. I haven't heard them yet though.
guidocorona OP
4,114 posts
 
The info on the X.5 series internal changes are still scant. The best info I have found so far seems to suggest changes in the power supply have been included. Here is an extract from an ad for the x250.5 on audiogon: ". . . addition of single-ended Class A bias, high speed fast recovery rectifiers in the power supply, and some changes to the front end circuitry have been made." I have not however seen a complete discussion of these changes anywhere yet.
guidocorona OP
4,114 posts
 
I have found the following snippet in a current Audiogon listing for the X350.5: "The new X350.5 features improved output transistors and a redesigned single ended Class A bias circuit . . . ."
jazzmeup
19 posts
 
I have owned X150, X250, X350 and now the X250.5. The X250.5 is by far the best sounding amp in the X series or maybe the X.5 too. I like the X250 better than the X350 and I assume the X250.5 should outperform the X350.5. The X250.5 is less aggressive, more sweet, relax, extended than the X250.
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