Syntax, I have never listen to the xa30 and 30.5. I would have like to do the comparison myself. one thing the new pass amps are more complicated design than the orignal aleph designs. The thing that made the aleph sound the way is does was the simplicity of the circuit. to me the purity of the signal is more preserved in the alephs than the new amps, this is what I believe and read about. I believe the xa.5 series amps has 3 gain stages vs 2 for the aleph and the xa.5 will go into class ab and the xa.5 I believe are push-pull amp, alephs are single ended. The alephs I believe has a shorter path to the output. Nelson pass made the xa series with the alephs output stage and the super symmmetry "x" front end, so what does that mean? I think he wanted to get the aleph sound back because, the "x" series did not have the sweet sound the aleph series did. I did listen an x150 and was not impressed, it sounded clean and dynamic but, it sounded more solidstateish, that is the word that comes to mind.
pass labs xa30.5 vs aleph 3
Stereophile reveiwer Erick Lichte has done a head to head review of these pass amps in August 2009 issue. Erick uses the aleph 3 as his main amp feeding a pair or Revel f30 speakers, he also uses Benchmark Dac1 to feed the alpeh as I do as well. He was asked to do a comparison between the pass amps as a follow up to the great reveiw of the xa30.5 which was reviewed by Brian Damkroger in which,I quote "absolutely, positively,and enthusiasticallly recommended" the xa30.5 and, Brian sounds like he perfers high powered amps in the review. In the review Erick thought the Xa30.5 sounded more resolving and a little bit better bass control and can sound louder than the 30 watts. It was leaner in the midbass than the aleph 3 but, had a slightly more presents in the top three octave. he still is in love with is aleph 3 and sound like he is not planning on replacing the aleph 3 with the xa30.5. Anyways I have been waiting for a head to head review of these pass amps since the xa30.5 was released. If anyone would like to see the head to head review send me an email and I will take a high res pictures of the artical and send it to anyone. Also Erick Lichte did a head to head review of the Musical Fidelity's 550k supercharger amp and the Aleph 3 in a December 2008 issue. He concluded the aleph sounded better than the 550's by itself. He then supercharged his aleph 3 but did not like the sound. Very interesting articals about my beloved aleph 3, and a great read for aleph 3 owners. In my opinion the aleph 3 is still a giant killer and is a legend when it comes to amps.