What Difference between Pass X150.5 and X250.5?

I assume the new Pass ".5" series of amps was only from the X250 and up, i.e. the current X150.5 untouched correct?

Teajay, you say: "X-150 became the X-150.5 when Pass decided to add the blue meter to the front of the amp, which the X-150 lacked. Otherwise, the amp was exactly the same." The Pass site seems mostly to confirm this, but they do give one measurement which is significantly different from X150 to X150.5: something called "Balanced CMRR" is given as " -85 dB @ 1 kHz" for the X150, but "approx. -70 dB @ 1 kHz" for the X150.5. This suggests that the amps do in fact have some significant internal differences, not just a meter on the front...unless you have heard otherwise from Pass themselves?

Calanctus, I have no information that would put in doubt what you stated on the Pass Labs website. I remember a long time ago that I talked to someone in Pass's office who said their was no sonic difference between the 150 without the meter compared to the 150.5 with the meter. The new 150.5, along with the whole new X-.5 series, is a different matter entirely. Remember, Eril, its not just class A biasing in the new series, like your Cairn amp, but single-ended class A biasing for certain amount of watts before going into regular class A. This gives some of the sonic virtues normally associated with tube SET amps. The 250.5 lives in a different sonic world than your Cairn Intergrated amp, which is great for its cost, but is not is not really competitive with the 250.5. But remember your comparing amps that are a least $4000.00 different in their prices. In this case more $ really brings a much higher level of performance, often more $ doesnot = better.

Thanks again Teajay.

Yeah I sort of appreciate the difference in the Class A stuff. I live in New Zealand. We get stuff all here so I import. The Cairn Fog 2 CDP and 4808A were my first venture into good audio. Loved it so now moving up. Started with Combak Reimyo CDP-777 - which is outa-this-world-wonderful - I don't want valves in a power amp and can't afford XA series. But I am also wanting a great valve pre-amp . Any thoughts on what works well with Pass X -5 series?

Two different Pass dealers say internals are the same between X150.5 and X250.5 - power and Class A bias are only real diffs - X150.5 goes over at 15 watts - X250.5 at 25 watts.
Nelson Pass himself says "authority and control are only big difference. The other audible differences are subtle."

Eril, you live in a beautiful country! The closet I have gotten to New Zealand was a trip I did to Tasmania two years ago. If the MAN himself, Mr. Nelson, says that's the major differences between his amps, who am I to argue. I would just add that as you go up in the X-5. series you get more and more of that special "organic" sense because of the higher single-ended class A biasing. I wrote a review here on the Gon about my experience which lead to me replacing an Edge-NL10 with the PassX-350.5 in my system. You might want to take a look at it. This "organic" sense is subtle in the Pass amps but after you hear it, its hard not to want it in your system. I think its time for you to have a home audtion and let your ear's decide what you like. Please share what your experience/decision is after you listen with us. Thanks.