Pass Labs A/B amps vs Class A amp and Actual Power

Stickman51, I would suggest having at least mininumly a foot and a half off the side walls. You could always put the Ribbon tweeters on the inside to avoid sidewall distortion. The space between the 20.1's should at least be five to six feet apart between the inside edge of the speakers. My 20's were set up this way in my old place and they still sounded great, now I have them more then six feet off the side walls and about nine feet apart and they sound even better. Hope this helps.

Remember, you want at least four to six feet off the front wall behind the 20.1's so they can breath.

So, roughly, with 1.5 ft from each side wall and 5 ft spread, a minimum room would be 13ft wide since 20.1 is approx 2.5ft wide...

Adding another 1.5 ft on each side (total of 3ft) would make that minimum 16ft wide and one more foot spread between the speakers would be a 17ft room...

Rtn1, I was merely asking a question, and based upon Nelson Pass's (albeit different) previous Class A designs, the question was appropriate. The Pass web site does list the XA 100.5 as "Leaves Class A at pk Watts: 200". I'm assuming pk means peak. Does that mean sustained power or short term peak headroom power and into what impedance load? It doesn't appear to be all that clear to me.

I just bought a new speaker which is a very demanding load - 87dB, 4 ohms, sealed enclosure. I first heard it with the XA30.5. It sounded OK. My XA100.5 made it sound much better, but still a bit closed-in during complex passages. I traded in the XA100.5 for the XA160.5 and what an improvement! Open, nuanced, dynamic and effortless. I don't understand it, but the control is better, scale and staging are better and ultimately, I'm more involved with the music.

I would buy the largest XA.5 amp you can afford. If it is not large enough, try the X350.5. Contact Reno HiFi for an in-home audition.

Unsound, there are detailed measurements in the review by Stereophile and further explanation in the Soundstage review. The Stereophile measurements on the XA30.5 estimate a maximum 150 watts into 8 ohms, and 200 watts into 4 ohms after converting into AB. So, this little guy in 4 ohms provides the first 60 watts in class A, and the last 140 watts in class AB.

Peter, your description parallels what I hear. I believe many people underpower their speakers. The XA200.5 sounds incredible at high volumes. There is no strain whatsoever. It is relaxed, effortless, perfectly dilineated, and majestic. I think that recorded music has an intrinsic optimal volume, but now it sounds so good even when blatantly too loud. If I play Mahler 8 or Gotterdammerung for the neighborhood, the needles on the front will flinch slightly at 400 watts into 90db speakers at 4 ohms. The other thing that is remarkable is how good it sounds at very low volumes, even the bass. Whether at a whisper or a roar, the Pass maintains a firm grip on all the drivers.