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

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.

Eril, in my last reponse I forgot to address your question concerning Pre-amps that are good matchs with the X.5-amps. I'm not an individual who is to enamored with tube Pre-amps, but let me share what I have heard with my own ears regarding the matching with the 350.5 in my own system. I replaced my highly regarded ML-32reference pre-amp with a Placette dual mono active line stage. It blew away the 32 on every factor(dynamics,transparency,soundstage,timbres,extenstion of bass,etc.). Not inexpensive, but a bargain at 4,500.00 dollars. You buy it factory direct with a full month audtion period with a full money back guarantee. Mr. Placette,Guy Hammel, is a great guy and a real gentleman along with being a genius regarding his Pre-amps. The other Pre-amp which sounds gorgeous with the X-.5 series is the highly rated, rightly so, Lamm reference pre-amp which is a hybrid tube/ss two box piece. However, it sales for over 12,000.00 dollars. The combination of the Placette active linestage and the Pass LabsX-350.5 is just exceptional in my system and I'm totally happy with this duo. Finally, someone I know has just changed his Pre-amp to the Herron tube linestage with his 250.5 and loves this combination. All three Pre-amps would really sing with any of the X-.5 amps along with many other brands/types of other amps. Hope this helps.

Info just in from Pass.
Per channel continuous:
X150.5 10 watts
X250.5 40 watts
X350.5 50 watts
With higher instantaneous peaks.

teajay - thanks for your thoughts. Auditions are impossible for Pass, Herron and Placette here in N.Z. I have heard several passives and they don't "do it" for me.
The Pass pre-amps are considered a little on the dry side by the Australian importer - I will buy from him, great dealer.
So I will continue my research on suitable pre-amps.