A review Bound for Sound for Pass Labs fans

I take all reviews with a "grain of salt" perspective. After all, their just someone's hopefully honest and somewhat informed opinion regarding the sonics of that piece in their system. However, I cut Martin G. DeWulf, publisher/reviewer of Bound for Sound, a little more slack then most for at least two reasons. 1) He has no ads so he does not have to "suck up" to any manufacturers for $. 2) He often prints negative reviews, if that's what he hears.

In the most recent Bound for Sound, DeWulf reviews the Pass LabsX-350.5, the first "professional" review that I'm aware of, regarding any of the .5 amps.

He states the following:

1) He thought that in the past that the X-250 was a great piece, but did not care for the performance of the X-350. DeWulf gives great credit to Pass Labs for not getting defensive regarding his past review that was negative towards the X-350 and being more then happy/fearless in sending him the new X-350.5. for review, he believes many other companies would not, if they recieve a negative review from him in the past.

2) He states that even with all the "Buzz" regarding the new digital amps, class D amps, class LMNOP amps, when people come over to hear his system, they all first get caught up in the "eye-candy" regarding the X-350.5, and then respond with, "That thing sounds awesome!"

3) He goes into great details regarding the build quality and new design changes that filtered down from the XA amps into the new .5 series.

4) DeWulf has auditioned many highly regarded Solid State amps such Ayre, Edge, Parasound, PBN Sierra Olympus and does a fine job of comparing the 350.5's sonics to these other reference single chassis or mono-blocks.

5)His final verdict regarding the 350.5's place in the hierarchy of world class solid state amps, "This is the finest solid state power amplifier that I've had in the Big Rig to date-long live the new king.

Well, I'm a big fan of Nelson Pass and the other guys at Pass Labs, I had the 350.5 as my reference (did a review of it here on the GON) only to be replaced by XA-100's, and am glad that this amp finally got the credit it deserves in a well done and through review.
Teajay, he must have been thinking of me amongst others. I could say my Pass amps just couldn't hack 1ohm, except that I ran them on 4 ohms, as well.

I haven't tried the .5 amps, although the X600 amps were always running on class A. They didn't need to be bias adjusted. The Pass guys are great. They are just up the hill from me. In cozier times, I dropped in on their headquarters. I would love to have them hear my amps, oh, and preamps.
Could you explain what you just posted ?
I am a Pass Labs fan. I'm happy to hear of a positive, even glowing review from Mr.Dewulf on the .5 series. But his review giving the nod to the X-250 over the X-350...I have to wonder if he had a case of that nasty wax buildup!
I also thought the X-150 sounded better than the X-250.The X-350 runs in class A for the first 50 watts. At most listening levels I'm in class A with my 350. I believe the 250 is rated 25 or 30 watts class A. Chalk it up to equipment senergy and personal preference. I have not heard a bad sounding amp from Pass, but I have heard Pass Amps that sound unique in their own way. I'm surprised that there are so few Professional reviews out on Pass Labs equipment. The Aleph series seemed to get the most attention.
Teajay, I'm in total agreement with your opinion of the Pass Labs crew... outstanding!
Wasn't the 350 supposed to have been the sweet spot in the pre-.5 lineup?

I wonder how much the eye-candy and impressing his friends had to do with the positive review.
Ozzy, check out my system. I ran the X-150 on 4 ohm speakers. When I got larger, less efficient 4 ohm speakers, the X-150 had no problem with those. The X-150 was running AB all the time.

In anticipation of getting my present speakers I upgraded to the X-600 amps, jumping over the 250 and 350. The 600 runs class A to 150 watts. The meter shows when it crosses into AB. It was warmer, and fuller than the X-150. Most of us liked the 600 better, but at least one favored the 150 on the 4 ohm speaker.

Then came the infamous amp eater. The powerful 600 stepped gracefully to the plate. I had no reason not to believe I was hearing the best.

On a report from another 1ohm speaker owner, I tried an ICE amp. The specs show the 600 a clear winner. S/N was 150 compared to 115. Power was 600 watts compared to 250 watts. Well, specs don't tell the whole truth.

With 93% efficiency, the ICE amp was actually in better control of 1 ohm. the ICE amp was far clearer too.

I sold that amp to a very happy deep pockets guy, whose awesome system is featured at Audiogon. Look for the third floor view.

Now, well just read my system review. There just is no looking back.
From my limited experience I thought the X250 sounded better than the X350. When I contacted Pass in Oct. 2004, just before the release of the X350.5, Peter said the X350 was not their best sounding stereo amp. He also mentioned at this time that out of the new .5 series amps the X350.5 was at the top of the heap. He has it in his own setup in his home.
I did purchase the X350.5 after my conversation with Peter Perkins and would agree with what has already been said about this amp. I used it with Thiel CS2.4 and the X600 with Thiel CS 7.2. As an experiment I tried the X350.5 with the big Thiel's and preferred the X350.5 over the X600. The X350.5 gave up a little in the bottom end, and I say a little, over the X600. However, the midrange and top end with the X350.5 was clearly better. The music just flowed and the top end was silky smooth.
Regarding the X600.5 I would like to hear from others who have auditioned this amp.
Ah, thanks for setting the record straight. It was your post about this some long time ago that I mis-remembered.
Thank you TeaJay for pointing out this new thread to me. . . looks like I will have to acquire a new amplification furnace for the Sweltering Austin Summers in some future. . . . or will Nelson Pass eventually create his own X.ICE amps? I am positive that if he ever decides to design them, they will sound just scrumptious.
Iris65... Peter would never endorse an amp in order of power. Nelson Pass himself said the 600 was the sweet spot in the X-series. Nelson Pass has also stated his new X.5 series and XA series just gets better with output!
"Nelson Pass has also
stated his new X.5 series and XA series just gets better with output!"

Gandme, could you please clarify the above? 
I'm not sure I know what you are saying. What I do know is the conversation I had with Peter concerning the X350.5. He said it was the best sounding amp in the .5 series. At this time the X600.5 was not out.
It was my opinion that the X350.5 was more to my liking than the X600. Nelson may favor the X600 over the X350.5. I do not know I did not talk to him about it.
Guidocorona, Irish65,
In a recent conversation with Peter Perkins of Pass Labs They feel the .05 an XA series get better with size or power, I don't know how else I can say it. Nelson Pass did say in the past that the X-600 was the sweet spot of the X series and The Aleph 2 was the sweet spot for that series. So that means they feel the X-1000.5 is tops and the XA-200 is best of that series. Good enough?
Yes thank you, I've got it now. This is interesting because in the past, the original X.1000 was not deemed to be the best of the old series by any stretch. But the X1000.5 is the very latest of the lot, so it will likely incorporate the learning curve from all previous models/efforts. Thanks again. Guido
Yes this may be true with the XA and .5 series but not with the X series. I think you might find more people preferred the X250 to the X350. This may also apply with the X600 compared to the X1000.
Gandme and Guidocorona, when I was communicating with Peter at Pass Labs at great length regarding if the XA amps, which did replace my 350.5, could power my MG-20r's in by-amped mode, one item that was clearly covered was that the overall sonic signature of the monoblock XA series amps does not qualitatively change, only the power/watts ratings.

This was very important, in that I noticed that the 350.5 at my loudest listening levels almost never left their Class A rating, which is around 50 to 60 watts. Therefore, it was decided that the XA-100's could drive my rig without distortion or compression. Otherwise, it would be on to the XA-160's at a cost of another $5000.00. Well, I'm no cheap skate and would have bite the financial bullet if I had to, in order to get the extra power if I needed it.

Well, I did not need the extra 60 watts of single ended Class A watts, to have the magic of the XA series in my listening room. But the major point regarding the three top XA models, 100's, 160's, and 200's is that their overall sonic signature is the same throughtout these monoblocks, the difference is their ultimate power ratings.
TeaJay, did the friendly crowd at Pass indicate to you if any member of the XA family could power the MG20R speaker by themselves comfortably, or if a byamping configuration is always recommended when applying XA amps to Maggies?
Guidocorona, the opinion was that if you were going to run MG-20's or 20.1's with their passive crossover and not bi-amp you would have to go up to the XA-200's. However, Peter believed that a pair of 600.5's might sound better because of the loading of the speaker, but no one I know has run the experiement comparing a pair of XA-200's to a pair of 600.5's on either MG-20's or 20.1's run in a passive mode.

I think its apparent that I believe the 350.5 is just a wonderful sounding amp, if I was not a nutty audiophile/music lover looking for that last bit of "magic" I could have lived with the 350.5 for a very long and happy time. However, the XA-100's are the most beautiful sounding amps I have ever had in my system.
Hrrrumpf, we truly need someone to run the experiment. . . in the meantime. . . I'll be checking real estate listings in Juno Alaska! The idea of being kept nice and toasty by a pair of X600.5s, listening to Herbert Von Karajan conducting Sibelius's 2nd Symphony whilst pulling up Whitings in my very unique music-room-ice-fishing-hut-combo sounds mighty attractive all of a sudden. . .
Mr. DeWulf also thought that the DK Design Group VS-1 Signature sounded just as good as the Pass, except he thought the Pass was MAYBE a bit better in the bass:

"I had to insert the Pass X350.5 with the Symfonia Opus 8 preamplifier to improve on the bass response of the Signature. That’s about $14,000 worth of solid state to surpass the bass performance from $6,000 of hybrid LSA Signature. And that’s not figuring in midrange and treble performance, where the Signature sounded more up front and immediate than any solid state system I could put together (including a solid state system incorporating the $25,000 XLH M-2000). "

I thought this would be interesting for all you avid DK bashers out there.
Nelson Pass said he thought the X-600 was the best in the series, confirmed by many owners of the X-series. But Nelson Pass never said the 250 outdid the 350. I think the 250 could matchup better in some systems & rooms...but not in most, including mine. I am not saying the 250 is not a capable Amp...but I enjoyed the match w/my equipment useing the 150 and 350. Tighter Bass, rich mids and detail galore at the top end!
Fair enough. We can both agree that Nelson makes some great amps.
If you get the chance you really need to hear the X350.5 if you havn't already.
I would upgrade to X-600s or the X-350.5 in a heartbeat! About the same price point used.
I'd like to know how many of our members have A/B those amps or owned them both.
I was just telling mitch4t, who has 4 X-600s and a X-0.2 on the gon... My wife would kill me in my sleep if I upgraded! I'll have to stuggle through the next year with my X-350 and X-1 combo!
It is a good thing to agree. They are great Amps!