pass aleph vs x series

Aside from power, do they share the same sound characteristic and general design/specs?
To some degree. The original X series sounded lean and cold, very much like stereotipical SS amps. But the .5 series adopted the Aleph topology for the first 50 or so watts, and added some of the signature sound that the Aleph are known for. I have an Aleph Os and an X350.5. When I upgrade to a new pair of speakers which allows for biamping, I am planning on trying to use both amps and see how it sounds.

But I think the air and dynamics are better on the X .5 series. (Take a with a grain of salt as I cannot compare them side by side. The Aleph Os just doesn't have enough juice to run my Thiel 3.6s)

Got to jump in here. I own the Pass Labs X-150 amp(not the .5). I think "lean and cold, very much like stereotipical SS amps" is a bit harsh, but I understand what the previous response was trying to say. The X series is a little on the lean side through the mids, but it is not cold sounding to my ears. I have compared this mp to an older CJ amp, and while the CJ amp is much warmer and tube like it is not in the same league. I have had many amps in my system including some hybrids. The Pass amp has been my favorite. I have also heard the Aleph series, and while it is more natural and tube like through the mids it is not as extended on both ends and not as dynamic. I don't doubt the .5 series bridges the best of the original X series with the Aleph series if you can play in that price range, I'd go for a .5 series (or better yet a XA.5 series - real big $$$). I think the original X series sound great when mated to a warm sounding preamp that can drive the lower impedance of this amp. Happy hunting.
I am an Aleph owner and have heard the X series on several occasions. I have never heard the X .5 series. While "lean and cold" is a bit of an exaggeration, it is clear to me that the X series transmitted a small bit of electronic artifact that the Aleph series did not. This characteristic of the X amps was clearly apparent when listening. If the X series had more slam, more dynamics, more power, a little better bass control and certainly better looks, I had a hard time understanding why people were paying up to own it over the amps which delivered neutrality, smoothness AND resolution, all at the same time. The fact that Pass upgraded the X to the X .5 while describing the .5 as more "Aleph-like" in his literature and publicity is his acknowledgement that something was missing in the X series. I do not agree with anyone who says that the Alephs are not extended in either the bass or the highs. My Aleph 4 has plenty of bottom and can easily rattle floors with plenty of deep bass. The extreme high end is sweet, detailed and has beautiful clarity. Triangles and cymbals ride on top of the music with clarity and detail. They are simply present when in the music and you don't hear them when they are not. The high end, particularly the upper midrange, is not as prominent as some other amps and you do have to be careful as to what equipment and cables you mate the Aleph with, but all the music is there. This amp remains as natural and neutral as any that I have heard.
The Pass Aleph power amps in general sound very natural and have great tonal balance accuracy verse the Pass X series.

The Aleph 0s power amp is one of the best sounding amps I have ever heard in my lifetime. The Pass Aleph O's verse a Pass X250.5 is night and day differences. Had both series amps in my system for a long time and I found that the Pass X250.5 has strengths in bass and definition, but honestly you can not listen too long without getting a listening fatigue. Verse the Aleph 0s power amp you can listen all day and feel very musical and warm sound. The Aleph 0s has a very impressive finesse midrange and plenty of transparency.

Now I am not saying the Pass X250.5 is a bad sounding power amp it's just very analytical and at times very overbearing which tends to give you a fatigue listening experience.

In essence the Pass Aleph 0s amp is a modest 40W pure class A power amp but 3-gain stage that can drive almost any speaker with ease. It seems to me that Pass gives you a trade off of more power with the X series amps and less finesse and natural accuracy. Vers the Aleph amps are more modest in ratings but have tremendous musicality and never a listening fatigue factor.

I still use both amps because the Pass X250.5 is in my home theater system for boom and bam type movie sound special effects.

The Pass Aleph 0s amp is in my dedicated reference 2-channel system when I want to do serious jazz & classical music listening for hours at a time.
I listened to quite a lot of the new Pass amps and honestly, they are boring compared to the Aleph 0 (when used with a proper speaker).
No life, no breathing, no body, no holographic picture, just normal clean hifi. I can not listen to them longer than 30 min, then I need a break.
But they look cool :)
I would have to agree with Rayhall with comparison between the Aleph Os and X350.5. Since my last post, I had upgraded my speakers to a pair of Verity Parsifal Encores. After consulting with Verity Audio to make sure that the Aleph Os has enough juice to drive these in my room, I hooked them up thinking that the X350.5 was probably an overkill (in terms of power) for these speakers.

The Aleph Os sounded exactly like what Rayhall had described. But my suspecion, confirmed by other Parsifal owners as well, is that these speakers required more power to make them sing then what's stated on the spec sheet. So our observation may be attributed more to the Aleph Os running out of steam than anything else. Once I hooked the X350.5 back, the speakers were singing again.

Since I have the Aleph Os out, I've meant to hook it to some smaller, more efficient speakers just to double check to make sure the amp is OK since it's more than 10 years old.

FWIW. I prefer the sound of the X series to the Alephs, but, I prefer the looks of the Alephs to the X series.
i was thinking about to trade my alephs O Monos for a x350.5 without ever have heard one. It would have been a 0$ exchange, more or less.
Just because of the fact that i have immense faith in what Mr. Pass is developping.

Here's what went through my head

1. my speakers don't need more than 70 watts, they are 89db, 4 ohms floorstanders with no critical impendance moves... I've ran them on 70w on 4 ohm tube gear before.
2. my room is just big enough to cool down the alephs. :)
3. i have a 1to1 comparison of my speakers with other gear in the quality range of the 350.5, according to high end magazines, and would NEVER trade the amps.
4. my amps came fresh out of overhauling at a certified dealer when i bought them a year ago

for all that, i refused to trade them... all the time i was investigating on the internet i was playing my gear plenty loud, without 1 minute of getting tired of what they did. This was in fact the most important reason why i stopped my trading activities.
Nevertheless, i would love to compare the Alephs to the new Pass amps. especially the xa 160(.5). Unfortunately it's kind of hard finding them for a reasonable price and with support getting them into your house. Maybe, one lucky day...