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
I know that there are some very knowledgeable Pass owners here on Audiogon, so I will not comment, as I found out that different models may sometimes use different topology.
Amarg, Kosst, Charles1dad, any ideas?
Bob
The Pass amps all share similar technologies but have slight differences in flavor.  As stated here many times before call Pass Labs they will be glad to discuss this and not pressure you into buying, extremely nice people and they also have exemplary service.

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.”

I’d strongly suggest you also listen to a couple of other amps:

Parasound - I like the sound better or equal for a lot less.

Ayre - I like the sound MUCH better than Pass

Personal preferences and speakers matter. My one point is, don’t get hung up on a brand unless you have auditioned the alternatives.
@erik_squires .
Good point!
Sometimes people get caught up with a name and don't consider the alternatives.
I love Ayre as well, but they work incredibly with the Vandy's. I don't recall if the OP mentioned his speakers? 
As has been mentioned often, synergy between components is something that must be addressed.
Bob
To be fair, I think Pass is a great designer. I wish I could afford his amps.
B
Post removed 
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. YMMV

If you can get one if Pass XA Amps, absolutions go with that. The class A amps are absolutely stunning and MUCH more powerful than the rating suggests.
There is a good thread on audio aficionado forum under Pass, were OP compares pass 250.8 and 260.8 monos. He clearly prefers monos. But 350.8 is different animal. Based on my conversation with Kent from pass the 350.8 a little more resolving and not as liquid as 250.8
agree that X250.8/X350.8 is personal preference, not one better than other...also many prefer the X series to the XA...Kent from Pass or Mark from Reno HiFi will get you as well informed as can be without an actual audition...
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?
XA Mono's > XA Stereo > X Mono's > X Stereo

Well relatively speaking anyway... Let your wallet decide.
I am auditioning the Pass Monoblocks 260.8 and sounds very promising with the Harbeth 40.2 speakers giving them the power that they need and bass I didnt know the speakers could get.  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..
what preamps are you trying karma ?
I was able to audition the Pass X 350.8 against the older model X350.5. 
I thought the 350.5 was more livelier.

ozzy
Good comments all, thanks and please keep sharing
I agree with ozzy in that I preferred the 350.5 to the 350.8.
I am auditioning the pass labs xp-22 and xp-12 to hear what an all pass system sounds like......I like the xp-12 but the xp-22 is easily better.....there must be a better combo out there than the xp-22 and 260.8 but not sure can be had without spending more perhaps much more......this just sounds so right....radiohead sarah vaughan david bowie john coltrane miles davis all sounding glorious on vinyl.....
It’s a great combo
karmapolice, can you please describe what differences you hear between xp-12 and xp-22? Is xp-22 in a different league in compare with xp-12 when  paired with 260.8? I am considering pass 260.8  but not sure if I want to have 2 pieces xp-22.
If you never hear the xp22 you will be very happy with the xp12....however the xp22 just sounds a little better in every way .....imagine a good pair of shoes versus your most comfortable.....

I didnt want a two box preamp....I wanted a one box preamp with phono built in but cannot deny I now finally love the harbeth 40.2 ....
@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)



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." 
Something we all forget about is combination. During auditions, I've heard the same amp sound substantially different based on speaker type, wire, source, pre-amp etc.
On many occasions I've heard the same amp that sounded awful on one speaker, sound pleasant on another. Change the pre-amp or source and they same can occur.
I am running the 260.8 amps on a very revealing speaker with dual AMT tweets per side and think this model is a great combo and mimicks the tubey warmth of other amps I've run.Other SS amps on these speakers can easily be too forward and/or thin.But the same amp in my theater (different speakers) sounds well balanced, dynamic and has great bass punch.
Scott