Review: Pass Labs X250.5 Amplifier

Category: Amplifiers

My past reviews have focused on preamplifiers, particularly the offerings of Conrad Johnson, the CT6 and the CT5. I have used tube preamps for about 10 years now, as I find their musicality superior to transistor designs. As no transistor preamps were used, I cannot comment on how the amp under review, or any of the other amps used, sound with a transistor preamp.

My listening tastes cover a wide range from large orchestral works, to jazz, to vocalists. For critical listening and comparisons, I use mostly CD recordings with exceptional sonics, and ones that I am intimately familiar with. I also use vintage recordings of less than perfect quality, as they reveal how a component will make such recordings more or less listenable.

In sound, I hate thinness, brightness, recessed perspectives, texture, grain, bunched images, constricted dynamics.

I value musicality and naturalness, along with clarity, resolution. I want some body to the sound, without having an overbloated effect.

I encourage you to read my reviews of the Conrad Johnson CT6, and then the CT5 before reading this review.

Since those reviews, I have changed speakers to the Von Schweikert VR4-SR, replacing the B&W Nautilus 802, which are retained in a second system.

I find amplifier reviewing both a pleasure and a pain. Contrary to what some claim, I find the differences in amplifiers immediately noticeable, and perhaps the easiest to zero in on, because they are near the end of the system chain, second only to the speakers.

Amplifiers do sound different. Some of this, of course, is due to speaker interface, but more of these differences are due to the designs themselves, in my opinion.

It is necessary, indeed imperative, I point out the substantial differences between the B&W and the VR-SR speakers. The B&W has a metal tweeter that emphasizes and brings forward upper midrange and lower treble. The VR-SR has a silk dome that is quite detailed and extended, even more revealing than the B&W, and this tweeter does not emphasize the upper ranges to any appreciable amount, though it is far from a laid-back or recessed sounding speaker. I did not find the combination of the Pass and the B&W to be as good of a match as the Pass and the VR-SR. I attribute this to the B&W's somewhat bright metal tweeter and forward response. I would not term the Pass a highly upfront amplifier, but neither is it retiring, and it seems the combination of the B&W's frequency deviations and the Pass not the ideal of combinations. Plus, realize the 432 that I was using with the B&W's is a rather laid back amplifier, hence a better match, as was the CJ 11a tube amp. The VR-SR has made me question metal tweeters. They seem to add their own sound, and it is one that needs taming by a tube amp or a laid back transistor amp. Hence, my comments below are based mostly on using the VR-SR.

Being familiar with the sound of the Levinson 432 and the JC1 on the VR-SR, the Pass presented some interesting differences.

Beginning with the suave and delicate Levinson, the Pass distinguishes itself as a different beast. I was somewhat slack-jawed immediately at the bass authority and weight of the Pass. Nelson Pass has said that MOS-FETs are capable of great bass, it's just that few designers know how to design a circuit that properly implements them. Based on the results of his design, I definitely agree with him. This amp crushes the Levinson and the JC1 in the bass department. As good as the JC1 bass is, the X250.5 is levels better.

The Pass has control, authority, weight, tightness, resolution, detail and dynamics. And I'm not talking about overdone, bloated bass. This bass is simply of the highest level I have yet encountered. It makes the 400w JC1 and 432 sound less powerful than the Pass' 250w.

Listening to an acoustic bass player running up and down the frets sounds as realistic as I have yet heard from any amplifier, and as integrated - top to bottom. The pluck, the size of the string, the overtones, the stage image -- it's all there.

In contrast, the JC1 could not define an acoustic bass line nearly as clearly and realistically as the Pass. Neither could the 432. On the JC1, the plucks were not clearly defined much of the time. The attacks were hearable only part of the time, indicating that bass definition and detail were missing in the JC1. This was a surprise to me, for prior to the Pass, I thought the JC1 bass quite good. I did many detailed and repeated comparisons on the numerous differences I heard, so I stand confident in my opinions.

Staging and Imaging.
The 432 is a champ at separating musical lines and placing images in a defined soundstage. The Pass does very well in this department, though the 432 has a more delicate and diffuse approach, whereas the Pass has a bolder, more fleshed-out persona. The JC1 tended to always sound pleasant with a subtle 'Halo' around the sound, which was always pleasant, but also obscured ultimate detail. The JC1 had some of the delicacy of the Levinson in instruments like flutes, triangles and vocals. On the Levinson, one could hear the breath on the attack more realistically and refined than on either the JC1 or the Pass.

On the JC1, cymbal clashes sounded somewhat splatty and died out too quickly, giving a somewhat lifeless or dead quality. Cymbals on the Pass were clearer, and perhaps a bit more upfront, though not excessively so, or objectionable. The Pass reproduced cymbals with a clear attack and a long, natural, expanding ring.

The JC1's percussion did not sort itself out as well as the Pass. The Pass excelled at unraveling all elements of the percussion, making the JC1 sound more confused, weaker, with less body, and more of a glassy edge at times.

The dynamics of the Pass let things grow more than either the 432 or the JC1. It always sounded more dynamic. This is ironic, as the JC1 are monoblocks, and the 432 is totally dual-mono, while the Pass channels share one extremely large transformer.

Since I love massed brass, the Pass brought me great pleasure. It recreated brass ensemble passages superior to the other amps. Instruments possessed a 3D image and clarity of separation I did not hear in the JC1, which sounded congested by comparison. Brass instruments swelled out into the air, expanding and blooming into the space, as they do in real life. The 432 was also capable of this, but did not possess the body of the Pass, opting for a lighter, more delicate detail, which showed again the deficiencies of the JC1 amps.

Vocals sounded good on all amps, but slightly different. Voices on the 432 were delicate and nuanced, but a little thinner with less color than the Pass. The JC1 is a good vocal amp. It gives a nice, natural sound to voices that sounds coherent. The Pass is very good, but sounds like the singer is a bit further away from the microphone, making the lip and mouth elements not quite as defined as the other amps. Don't overreact to this, as it is a small thing, and only noticeable when switching between amps.

The Pass does so much right that I must say it is the finest transistor amp I have had in my home, and it is now my reference amp. It is free of any grain or texture, has clarity and definition, yet is not bright. It has a huge soundstage with great lateral spread and very good front to back perspective. It gives almost a tube-like body to instruments; a lovely weight that sounds natural and not overdone. It is unique in that it has this lovely body and natural weight, yet it does not color the sound in achieving this. Indeed, poor recordings will reveal their flaws, but they will also reveal what is good about them as well.

Many others have stated on this site and other sites and in magazines that this latest .5 series weds the Aleph design with Nelson's newer X series design, and I believe that is true.

I don't think this review would be complete without mention of the physical attributes of this amp. It is a gorgeous, imposing piece, with a faceplate nearly as thick as a dictionary, beautifully finished, combining modern with industrial. And the beautiful geometrically sculptured faceplate that has the haunting round blue meter that is mesmerizing and beautiful.

The X250.5 has gained a permanent place in my system. Thank you, Nelson, for making a piece of electronics that allows me to just want to sit and listen to the music and forget about the equipment......!
Zear, excellent review, Mr. Pass really hit a sonic "homerun" with both the X.5 and XA series amps. I felt the same way about the 350.5 when it was my reference until I moved on to the XA-100's that even give a little more magic if you don't need tons of current. Thats's even be addressed in the new XA.5 series that does double down into lower impedance loads. Thanks again, for a wonderful well written review.
Thanks for your kind words, Teajay. I know what a Pass fan you are, and you have shown your enthusiasm in sharing it through your many forum posts and reviews. I would go further to say I find your postings honest, with no self-serving interests behind them, doing it out of a sense of audiophile generosity and sharing that needs to be commended. Not all who post here have that attitude. So, thank you for that.

I did not mention the XA series, as I have no experience with them, though I have read your comments and praises. Unfortunately, we all have price limitations and must stop somewhere!
Somehow during the posting of my review, my equipment list got eliminated. So here it is:

Von Schweikert VR-SR speakers
Conrad Johnson CT5 preamp
Conrad Johnson CT6 preamp
Northstar transport and DAC
Mark Levinson 432 amp
Parasound JC1 amps

Various cabling
Fab review Zear!! TeaJay, any plans to taste test the XA100.5 or any other XA.5 models?
Guidocorona, I again talked to Kent last week regarding if their is sonic difference between the XA and XA.5 series if you do not need to double down into lower impedances, his answer was you cannot tell the difference if you do not need the extra current for your speaker load.

So, my XA-100's are going to stay, remember I biamp my MG-20's and the XA-100's have no problem powering the ribbon tweeter and midrange panels.

Thanks a lot for this great review. Being a fan of Nelson Pass myself and especially of X250.5 amp (mostly because of its excellent price/value relation) I can only confirm your experiences with this amp. Really great peace of HiFi kit ...

Thanks for the compliments. I tried to describe the very fine sonics and benefits this amp design has to offer. The price has also increased to $7,500 as of June 1.

I recently found out that Pass dropped all their US dealers, and are in the process of slowly rebuilding a new dealer base. So, there are only a few authorized Pass dealers in the US at this time. It is said they have so much business overseas that it isn't hurting them to revamp things here to more tightly control their product distribution.
There are many on this site who own and praise Pass amplifiers. There are also those who do not personally like the Pass. As I recently posted on another thread (McIntosh 402 or Pass X150.5), I believe the matching of components and cables plays a larger role than some realize. In addition, people listen and hear differently, and have sonic preferences.

For those who do prefer other amplifiers, I am glad they enjoy them. But I also don't agree with some of their criticisms, particularly that the Pass is bright. It seems that a number of those feeling this way are McIntosh lovers.

Although I haven't heard the latest McIntosh solid state amps, I am familiar with the MC352, which I believe the 402 evolved from. I found the McIntosh sound to be somewhat dark, veiled, rolled off in the highs, and not as expansive in soundstaging or imaging.

Now, if you have a speaker with a bright and/or forward sounding tweeter, particularly metal domes, you may have a better match with the McIntosh. Having said that, there are a number of Pass owners on this site who have speakers with metal domes and find the Pass anything but bright. I myself did find it bright on Nautilus 802's, with hot or bright recordings. That's where the rolloff in amps like the McIntosh can produce a more pleasant sound.

What people forget is that their cabling needs to compliment both their equipment and the recordings they listen to. Some will say this is going away from neutrality and using colorations. Well, if it is, so what? The recordings we listen to are not neutral and accurate in most cases. Ideally, we might have two sets of interconnects and speaker cables to swap out for our wonderful sounding recordings and our tipped up, equalized, compressed recordings.

I like my Pass, because it gives natural body to the sound. Yet, at the same time it recreates a wonderful soundstage with height, width and depth, while it unravels details in a natural, unforced manner, and never in an overetched or overdefined way. Add its striking dynamics and bass reproduction that is levels above any other amplifier I've heard in the $10,000 or under range. At its prices on the used market, it is an absolute bargain.
Very good review. It reminded me of a listening session I was involved in where the X250.5 and four other amps were compared ---the Parasound JC1, a Krell, a McCormack DNA500, and a Belles 350. I picked the Pass amp as the best sounding of the bunch. It was just more natural and realistic sounding. I agree with you that it has a full bodied sound, which I think was part of its realism to my ears.