Pass Labs XA30.5 and ModWright KWA150

Has anyone directly compared these two amps, who could describe the differences in sound? Both are said to be among the most "tube-like" SS amps, and are about the same price.
Post removed 
Thanks Tvad for the response. Indeed I was asking on the assumption that the speaker load was not a major factor in the comparison. However, your descriptions of "superiority" and "class of its own" are not really helpful because I am looking for a neutral and detailed account of differences in sonic flavor using various kinds of music.
Post removed 
I never heard the Modwright but I have heard the XA-30.5 and all I can say it is one sweet amplifier. I heard it through a pair of Salk HT3 which is a very difficult speaker to drive and the Pass handled it effortlessly.

I know Modwright is also great stuff so this would be a hard choice for anyone.

Good luck.
Why not just get a tube amp if you are looking for "tube like" sound?

In my system I was able to directly compare the Pass XA30.5 to Atma-Sphere M-60's and MA-1's and there wasn't a single area that the Pass came out ahead from a sonics perspective. The Pass will come out ahead in being more compatible with a wider range of systems when compared to the similarly priced M-60's.

The Pass amps are excellent and right up there as my favorite ss amps, but I'll take the Atma-Sphere amps every time.


I too had the XA30.5 and M60s at the same time driving Merlin VSMs. The Pass is by far the best SS amp I have ever heard. I kept the Atma-sphere M60s, as it was the best amp I have ever heard driving the Merlins. I have not hear the Modwright, so I have nothing to say about it, but I do get the feeling that the XA30.5 will be remembered as one the very best amps Nelson Pass has ever made, and that says alot.
I also agree with some posters here that Pass amps don't really sound tube-like (I had a 250.5 though, not the XA series)

The SS amp that sounds like tubes to me is McIntosh.
you are looking into "the most "tube-like" SS amps " then you MUST check Spectron amplifier !!!!!!!!!!!!!

I owned a number of tube amps and the last was a McIntosh ...but no comparison with Spectron.

As a Spectron owner, it is not tube.

I have owned McIntosh MC 501, it's far from a good tube amp.

Bottom line, tube rules. I am keeping my BAT 150SE.
I've not understood the need for a low-powered SS amp. If my speakers just needed 30 watts, I'd get a tubed amp.
As Semi said, the Spectron sounds nothing like a good tube amp. I am not saying the Spectron sounds bad or is a bad amp, just that I can't see anybody remotely saying it sounds like a tube amp.

My statements are based on having the Spectron amp in house for an extended audition. During this audition I was able to directly compare it to Pass and Atma-Sphere amps.

Tube-like to me means: Dimensionality of images, bloom and decay, a sense of instruments actually present. Then why not just get a tube amp? Well, issues of maintenance and heat, along with typically lower damping factor. Some pure class A solid state gear gets you part way toward tube sound (but never all the way of course).
Right. The Pass will run near as hot as a tubed amp with similar power. The Pass is overbuilt and is essentially no maintenance. However, if you have a speaker that can work well with a tubed amp, and you are looking for something that sounds like a tubed amp, then buy a tubed amp. You will spend more time trying to get the SS amp to sound like a tubed amp, than time spent with any maintenance issues that are likely with a tubed amp in the first place.

There are some good choices with autobiasing, good customer support, and very good build. You can often find something with an intact warranty at a used price from dealers.

SS amps can work very well, but they take much care and effort.
A Pass amp that works a bit more like a tube amp, especially in terms of damping AND being a very easy load for the tube preamp would be the First Watt Aleph J if you can find one used. I think it works extremely well with smooth and highish impedance speakers (tube friendly speakers).
If you want tube-lie or better amp then look at Spectron amplifiers. One of the reviewers wrote:

"...when the original Musician III arrived for a review, I took the opportunity to ship the [VTL] Siegfrieds back to the factory"
- W. Donnelly

I amnot saying "run and buy it ASAP" but investigate, IMO, you must

All The Best
"Tube-like to me means: Dimensionality of images, bloom and decay, a sense of instruments actually present... "

According to these criteria Spectron is the best "tube-like " ss amplifier I auditioned or owned. (There are very few other ss amps standing at this level or may be above but all are much more expensive)

Two people disagreed with this statement:

1) Semi who found combination of Athma-Shere and Merlin speakers to be better: YES, I AGREE WITH YOU. I visited Merlin room at last RMAF where it was matched with another OTL amp, Joule-Electra - YES, it is match made in heaven. BUT - OTL demands large degree of maintaince and OTL cannot drive well speakers with low impedance. For these reasons I do not own OTL and I presume many, many others too.

2) Zybar who compared it to simply excellent BAT VK150SE (at $18k retail, last time I checked). In order to compare more or less fairly "apple-to-apple" he must have Spectron monoblocks with all upgrades (about $11k last time I checked) and he did not specify it (yet...).


Please go back and re-read my posts.

First, I compared the Spectron to Atma-Sphere amps, not BAT.

Secondly, I compared both the Atma-Sphere MA-1's (which are around $18k) and the Atma-Sphere M-60's (which are similarly priced to the Spectron amp). So there was indeed an apples to apples comparison in regards to price.

I also had Pass gear (XA30.5)in which to my ears had more "tube like" (as defined above) qualities than the Spectron.

One last note...yes, OTL amps do require more careful speaker matching, but you can use minimize that issue by using a Speltz Zero Autoformers.


Hi Zybar,

Yes, you are correct. While I do stand by my writing but I have toi admit an error: instead of "Semi" I wrote "Zybar" and vice-versa.

As I said I love sound of OTL amp when speaker can be matched appropritely. What is rather strange for me is your statement:

"One last note...yes, OTL amps do require more careful speaker matching, but you can use minimize that issue by using a Speltz Zero Autoformers. "

So designer of OTL amp believes that output transformer is BAD (for his varous reasons) and did everything he could to create...OTL (OutputTransferLess) amp and you saying basically to him - you did huge job to eliminate output transformer but I will install it into the signal path ANYWAY and destroy your intention and your goal...and your sound.

You surely has any right to do whatever you want but.... logically isn;t it better just to buy amp WITH output transformers already installed and voiced by the designer? Here we mentioned, for example VK150SE amp... there are others also good but less expensive
Post removed 
I agree, though I have never heard the ZeroFormers with the M60s (don't need them), there is something about the very idea of it that doesn't quite feel right - even if they work.
Because it might still sound great with an autoformer. For instance, it is still a Class A, triode amp. But I do agree with the general idea (not based on any technical knowledge at all)that there is some dissonance in the idea of using an autoformer when you have purposely decided on an OTL amp.
I agree with all of the statements about using an Autoformer (I don't use one and this is one of the reasons I went from M-60's to MA-1's) with Atma-Sphere amps.

When I ran tests with and without the Speltz Autoformer, I could always pick out when the Speltz Autoformer was being used. Anybody who tells you that it doesn't have a sonic signature is definitely fooling themselves - it is there.

However, Atma-Sphere amps + the Speltz Autoformer still sound better to my ear than most amps I have tried. The sonic penalty you pay for inserting the Speltz Autoformer isn't huge and is far less significant than the sonic improvement one gets by raising the impedance that the amp sees via the Speltz Autoformer.


OP, if tubes are out of the question for you, I would go with the Pass XA.5, it really does not get better than that if 30 Class A SS watts is enough to drive your speakers.
Post removed 
All good points Tvad. I tried the Speltz Autoformers with the following speakers:

Vandersteen 5A's
Emerald Physics CS2's
Omega Revolutions (8" Alnico driver)

Ultimately, trying things at home is always the best course of action.