My earlier comment about sound superiority when compared the XA60.5 against a Stereophile Class A amplifier was based on using single-ended connection. My preamp is also in the Stereophile Class A category. Its manufacturer has a radical viewpoint that balanced connection does not make a difference in light of their well crafted circuitry. So back then there was that lingering thought about perhaps my preamp could be eclipsed by an different preamp of equivalent pricing but with balanced connection. I am known to be picky and difficult on just about anything, even as my preamp sounds pretty good and is well respected by enough professional reviewers. Yet after getting the pair of XA60.5 and am so surprised at their performance, I have resigned my concern.
The point here is more about Class A amplifier than about Pass Lab. I just dive right into Pass because they are the measuring stick and the bridging gap when people attempt to compare solid state amplifiers to tube amplifiers, with each category having its own strengths. But I would think a few upper-end Class A amplifiers beside Pass could somewhat portray what I am talking about.