Recommend Class a Amp

03-28-15: Abrew19
If you value bass quality, ignore what Tjassoc wrote above regarding the low wattage Pass full class A amps. While I haven't owned the xa30.5 I do own the older Aleph 5 which is a 60wpc full class A model. AND I also own the newer x250.5 which is the 250wpc class A/B behemoth. So I do direct comparisons frequently. While the full class A Aleph delivers absolutely delicious mids and high frequencies, the bass quality isn't great.

I would not extrapolate any conclusions about the bass quality or any other aspect of the sonics of the XA30.5 from experience with the Aleph 5. They are completely different designs, starting with the fact that the XA30.5 is a fully balanced design while the Aleph 5 is not only not balanced but is not even push-pull, being single-ended.

That said, I am not asserting that the XA30.5 would be a suitable match for the QLS-1. I couldn't find efficiency or sensitivity specs for the QLS-1 (although I note that it is recommended for use with amplifiers rated from 100 to 500 watts), but I suspect that its efficiency and sensitivity are much lower than those of the Wilsons Tjassoc referred to, as well as its impedance characteristics being difficult. FWIW my guess is that the XA30.5 would often be struggling to some degree when driving the QLS-1, especially with recordings having loud orchestral peaks or other instances of wide dynamic range. I say that despite Stereophile's measurements indicating that the XA30.5 can provide 195 watts into 4 ohms (more than twice as much as the Aleph 5, btw), although not in class A above about 60 watts.

Regards,
-- Al

I drove Martin Logan CLS IIz for years with McCormack monoblocks and they never failed me. Best sweet sound I ever experienced, and those speakers were not exactly ballerinas.

As stated, a Pass INT-30A owner:

While I've not heard other low watt Pass designs, I completely agree with Abrew regards the trade off: even with high efficiency speakers (Al, I'm now running the Ulysses :), you are trading low end authority for super yummy mids and highs. The very fine Odyssey dual mono that my Pass replaced was conspicuously superior down under (up the range, not so much :)

I mostly listen to "small" music, particularly of the "girl with guitar" variety, so as Mark at Reno HiFi promised, a good trade off for me.

But I think, not for everybody, depending on speaker preference and listening habits.

John

Wow! Congratulations, John. I seem to recall that you were thinking of the Ulysses a while back. Hope you are enjoying them as much as I do mine!

And re the INT-30A, I **would** expect your experience with it to be likely to have relevance to the XA30.5, in contrast to what I said about the Aleph 5.

Best regards,
-- Al

Almarg, yes I know you are right when you said we should not lump the Aleph and XA.5 designs together. For that reason, I almost didn't comment at all on the post about the xa30.5. But I have heard too many commentaries from xa30.5 owners that sounded similar to my own experience with the A5 to ignore a conclusion. Even Pass factory folks themselves are aware of the pros and cons of both A and AB designs (hence the reason they offer 2 separate designs of course) and they are always interested in 2 things when you probe for recommendations, especially regarding their class A amps: what kind of music you will be listening to, and what speakers you will be driving.

I own B&W speakers that are not inefficient but which respond well to the grunt that the AB designs deliver. They specifically recommend the AB designs in my specific application over the class A models.