Pass XA200.8 Review - Fun measurements

@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!

shadorne,
i have nearly all from Benchmark, all dac models and amps. Used the AHB2 in mono on Tannoy GRF90 through very good tube preamp. Very nice sound, fast and dynamic, which to me are the strong points of these little marvels. Tried the XA160.8 on same: so much better in just about every aspect of sound; especially tones, bass, coherence, soundstage and overall musicality. No comparison. But i still love my Benchmark gear. They are better adapted to other speaker types, and Pass is very well suited to Tannoy in general. Nelson Pass does lots of evaluation on Tannoy, and Desmond Harrington, president of Pass has Tannoy at home!! As much as I think we can say Pass XA are not adapted to the Wilson.