Pass Labs:What to expect fm XA60.5 to XA100.5


Hi Guys,

Some of you may know that I have some buzz/hum issue in one of newly received XA60.5 mono blocks. The dealer diagnosed the problem and determined the transformer needs replacing. Since the XA60.5 is only few days old so I am given the chance to get a replacement set or I could top up the price difference to get the X350.5 or XA100.5s when my dealer gets their stocks in the next 3-4 weeks time.

Kudos to Pass Labs and the dealer's service for all the patience and after sales services...certainly very much appreciated and glad I go for Pass Labs.

As such, I have 3-4 weeks to listen to the current XA60.5 in my system while waiting for the stocks to arrive and make the final decision on the swap/upgrade.
elmerpoh
Pubul57,

I too have found that smaller wattage amps will generally have a sweeter/purer sound. In decision making, I always go by my ears first then work backwards with my brain to see if there is a reason for a finding, but always ears first as they are "direct coupled" to my wallet.

This has held up even with my sub-hobby of vintage receivers. I prefer the sound of the lower watt ones to the monsters of old. What I have read (but don't know first hand) is that a lot of "music lovers" prefer the sound of the Marantz 8b to the 9's and the Mac 225 to the 275. Of course the speaker, and how loud you like it, are important factors.

I have a hunch one reason might be transistors and their non-linear characteristics. The more of them you use, the more NFB you need to get the amp to "spec" right. I personally don't like NFB.

My ears like what they hear in Pass's XA.5 series and this is from a guy who loves/has 4 SET amps. I have their 30.5 and 100.5's. Don't hear much difference beween the two. From what I've read about the design, running the Mosfets in pure class A, he can put them in their most linear range and therefore use much less feedback to correct. In his paper on the "Super Symmetry" circuit, he says he uses only a tiny bit of NFB to tweak the two circuits into balance so they cancel distortion. This may be why "his" larger amps don't lose don't lose the sweetness like other designs do. His papers on the Passlabs website are a good read.
The man is on of the greats, and owning most any amp he has had a hand in is a pretty good thing. Loved his short-lived 25 watt, Aleph J which should be great with most any 89-90db or higher and smooth impedanced speaker, maybe as good as the XA30.5 with my speakers and very easy to drive with a tube preamp (240kohm input impedance).
Nice comments Pubul57 and onemug. I believe you need the appropriate power to match the needs of a given speaker. I`ve personally have never been convinced by the arguement for gratuitous power i.e. one can never have too much power.

I`ve experienced enough examples where a lower power amplifier of equal built quality but simpler design and fewer parts(less complex) just sounds better(as long as the speaker is suitably efficient).
I agree with Onemug. Somehow, the XA200.5 sounds sweet, delicate, and holographic in addition to all the other things we associate with ample power. I suspect most other solid state amps sound hard and flat as a result of their more complex design.
Sounds like there may be no sonic price to be paid as you move up the Pass like, just the cash price (when you need the power).