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Pass Labs - 350.8 stereo vs. 260.8 monos

I have never owned Pass labs amps. However, someone as successful at designing/manufacturing Class A and AB amplification over the long haul as Nelson Pass has to be close to perfecting their craft. I prefer mono amps for the usual reasons but am not against a great-sounding stereo amp. I currently own big Class A mono amps as well as a Class AB stereo amp and based on my listening experience I believe there are sonic trade-offs that make both Class A and Class AB amplification attractive for different reasons.

I am curious about the sonic differences between the Pass X350.8 and X260.8 monos. I noticed with the exception of the obvious power differences, the two amplifiers (and all the amps in the P8 line) have similar specifications. A couple of differences in specifications that stand out to me between the 350.8 and the 260.8s are maximum current (35A vs. 28A) and the wattage at which the amplifiers leave Class A and transition to Class AB (18wpc for the 350.8 and 34wpc for the 260.8s). In this area, the big X600.8 monos seem to be the best of both worlds as they do not leave Class A until 100wpc! I just don’t need that much power.

Although I found a review of the X250.8 stereo amplifier, I cannot find anything on the X260.8 monos so I am hoping some of you have auditioned or own the 260.8s and/or 350.8 and can share your impressions and maybe comparisons to the P5 line or comparable amps by other manufacturers. Thanks for any insights.
mitch2

Showing 5 responses by mitch2

mitch2 OP
4,236 posts
 
Thank you @gdnrbob and @shannere
I will give the folks at Pass a call next week but I would also enjoy hearing from any Pass owners here on the forum. The amps are so well made, it would be nice to go a step up in the prior line (i.e., 600.5 monos) but it seems the P8 series amps have used technology from the XS series amplifiers to significantly improve on the P5 series as indicated by the following comments taken from two different reviews of the X600.8.
The design of the X600.8, and indeed, all of the .8 series, is similar to the Xs 300. The differentiating factor of the .8’s and Xs from the .5’s is the presence of a high power current source that is separate from the output devices. This allows deeper and punchier bass.
and
In the owner’s manual for the X600.8, Nelson Pass writes that his goal was to advance the key elements of the older amps to the next level. This wound up involving more of everything. The X600.8 uses bigger hardware that is biased more deeply into the Class A operating region. The front-end circuit is more sophisticated and customized for each model. The power supply also is beefier. And, finally, there are those heat fins – larger and more abundant to carry off the extra heat. The solid-state front end uses a mix of JFET, MOSFET and bipolar devices made by Toshiba. The parts actually have been discontinued, but Pass believes so strongly they are superior to anything else that he ordered a deep stock to allow both construction of new amps and repairs. “The result is a front end with high stability, low distortion and (low) noise,” Pass says. “It has a very high input and is DC-coupled. There are no compensation capacitors — in fact, there are no capacitors in the amplifier circuit except across the shunt bias regulators and the power supply.”

mitch2 OP
4,236 posts
 
Not really interested in the 250.8 but I like the thought of 34wpc of Class A from the 260.8 monos.   Anybody here own the 260.8s and can comment on their drive and bass capabilities as well as overall musicality?
mitch2 OP
4,236 posts
 
Good comments all, thanks and please keep sharing
mitch2 OP
4,236 posts
 
@karmapolice  
"As for its musicality that is the most subjective aspect of the audition and am trying various preamplifiers to determine if it has that specialness for my room......so far looks like a keeper.."
Have you yet resolved your question about the musicality and "specialness" of the 260.8s?  I am a little concerned with the comment by @rsf507  
"I've heard several Pass amps over the years, great build quality but each time they never moved me. It's like there was no soul to the music."
I have owned Class A, AB, and D that all sounded pretty good.  Currently I have a pair of high-powered Class A amps that do most things very good but I am interested in a slightly different sound.
The amps must have;
-power - at least 250/500 wpc into 8/4 ohms
-dense, rich tonality
-dimensionality - particularly in the midrange (Class D fails this one)
-deep, powerful, well-defined but not overly damped bass
-realistically extended high frequencies (not overly feathery or unnaturally extended or emphasized)
-fluid - cannot have a hint of an electronic or hard sound (Classes A and D have done a better job of this than Class AB in my experience)
-sense of "aliveness" particularly on music that is recorded to sound exciting - Class AB does a pretty good job here IME (the Class D amp I owned with stock NC1200 boards fell short here)



mitch2 OP
4,236 posts
 
Maybe this quote from the Dagogo review of the X260.5 amplifiers describes what @rsf507  was referring to in his description of the Pass sound....
"Another thing I noticed about the Pass Labs X260.5 amplifiers was that, even though they were powerful and dynamic sounding as well as musical, there seemed to be a sense of a type of “restraint” on the music, a sort of “holding back”. Sort of like a power/speed governor on a lawn motor engine, it seems to restrict the amplifier from fully “letting go”, of blooming and expanding unrestricted and quite possibly, preventing the amp from distorting. This invisible “ceiling” seems to somehow restrict the energy and flow of the music “downwards”, by not “letting it go” and allowing the music to flow out, just like it does in real life." 
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