Pass XA200.8 Review - Fun measurements

I think that the Pass X series is their best all around amp. I have the new Pass XP-22 preamp and the Pass X350.8 amp. They produce a very detailed and somewhat tube like sound with excellent sound stage. 
While this system is expensive, you are paying for excellent sound, reliability and product support that is second to none. In fact I had Mark at Reno Hi Fi steer me away from their class A amps because of their lower power and high heat output. I run this system with an 
Allnic H 7000 phono amp (tubes) and achieved an excellent result. 
The trick with a Pas system is to have a tube phono amp like a Herron,
Audio Research or Allnic.

Finally, to me, tube power amps are a real hassle to maintain. Their reliability is far below that of a Pass which is built to last and maintain its sound level. Tubes (especially power tubes) deteriorate over time.
And they have reliability issues because of poor QC in the factories that produce them. 

 

@shadorne - Agreed. 

30 years ago I made a purchase primarily based on measurements and it turned out to be something I was not happy with. Since that time only purchase based on how it sounds, but will look at specifications for component compatibility.

To the OP's question, I think there is undeniable distortion in the amplifier's output. This appears to be by design. In the review of the 200.8, Pass is quoted: 

"The lesson of the Xs and SIT amplifiers was that a small amount of second harmonic of a particular phase character gives a desirable sonic result. To get that effect, we altered the arrangement of the constant-current sources in the output stage to better duplicate the sound of the Xs output stage. While the .8 amplifiers still have low distortion, they do not suppress second harmonic as much as the .5 series, giving a mostly second-harmonic character at ordinary listening levels and segueing into third harmonic at higher power."

Also: 

"I don't think the audiophile wants technical perfection. He wants to be happy.—Nelson Pass"

Read more at https://www.stereophile.com/content/pass-laboratories-xa2008-monoblock-power-amplifier#EuGPmgvtCD4uc...

Great points about the distortion though. I own a Pass amp and am extremely happy with the euphonic distortion. I personlly appreciate Pass's approach to amplifier design. 

yes, it is, and they say so themselves, but a bit in a disguised way. They built amps for what one hears, not for measurements. If one likes the sound, who cares of measurements?? which even excellent sounding tube amp measures well... none!!
either you buy on sound quality/performance, or on specs/measurements. My Benchmark AHB2 are good amps and measure brilliantly well, but in performance against the Pass, not many will choose the Benchmark!