Pass X150.5 vs. X250.5

Using Vandy 3a sig with Pass 150.5 currently, and average listening level brings meters to around 11:00. Wondering if there was anything to gain by upgrading to 250.5. Just seems to get a bit harsh sounding on peaks.

I have owned two Pass amps. The meter at 11:00 isn't pushing the amp all that hard. So I'd be a little surprised if the harsh peaks you are hearing are attributable to the amp being overtaxed. I therefore think you should look elsewhere in the system for the source of the harshness, before you consider changing amps.

Perhaps not. There is not much more class A headroom between those 2 models. You would be going from 10 watts to 15 watts into 8 ohms. You'd probably need to go to the XA60.5 to get an improvement, but it depends upon the size of your room. With a big room, you may even need to get the XA100.5, or a more efficient speaker.
Kind of figured there was not much to be had by going to the 250.5. The speakers are average efficiency, around 6 ohm if I remember correctly. The room is roughly 13x18x8, so about average too. Ww carpet on floor, some absorbers at first reflection, no real furniture to speak of other than 2 cabinets on side walls. Using Pass X2.5 pre, all balanced Acoustic Zen Matrix Reference, Kimber 12TC double bi-wire to speakers. Playing with speaker position and tilt forever! Guess that is the direction to go for now!
I owned the 150.5 in the past and have spent a fair amount of time listening to their amps. I currently own an Aleph for a specific pair of speakers in which it matches well (60/90 watts 8/4 ohm, all class A). IMO, buying a/any Pass Labs amp should be based on your anticipated amount of required power being able to be driven by said amp when it is still functioning in Class A.

My experience with the Pass Labs amps is that their performance when it moves from Class A to A/B changes notably. In AB they are decent amps (not great amps) and become strident in class A/B versus their characteristic sound in pure class A.

As the poster above stated, going from the 150.5 to the 250.5, while delivering more total power, its added power in Class A that is important. In this sense, it is not a big increase (if you look outside of just the percentage increase - 10 to 15 is a 50% increase - but still not much in class A).

Have you assessed your power delivery? I owned an X150.5,
and it drove my Avalon Avatars to acceptable levels on music. It did sound somewhat worse when I drove it very loud. I decided that the (1) 15 amp breaker servicing my living room wasn't enough.
This is already after I ran a beefy extension cord from the kitchen, and put my front end and Video on that breaker.
I'm planning on dedicated lines, soon..
I have (2) James EMB-1200 subs. I'm only using (1), until my dedicated lines are in.
You may be experiencing dynamic compression, due to lack of power to your system...
Does not seem like an issue that will be solved by going from 150 to 250 watts (not much of a difference in dbs)and I think the 3As are fairly easy to drive and your room is not all that large. Is what you are hearing so apparent that it must be something other than a Class A versus B issue?
Where the meter sits is completely arbitrary, some sit at 12, some sit at 11, others wherever. What matters is if it moves. If it sits and does not move, then there is no leaving Class A. If it bounces all over the place then you need more power. The X250.5 is definitely a jump in power, but as many have pointed out it is doubtful that is your problem, it is most likely something else in the chain. Is the X250.5 a better sounding amp, to me yes, but if you have fatigue it is probably something else.
What is your source?
Acurus makes a very important point and I agree 100%.
What is the location of your volume control knob?
Does your meter move from class A to AB?
Yes, Pass meters only reflect Class A to Class A/B (unlike McIntosh meters). if it is moving a lot, you probably are underpowering your speaker.
A Vandersteen 3A? In that size room? You might be underpowering, but I would think one is listening too loud if that is the case with an X150.5 - no? - I mean, that is a lot of power for that speaker especially a 87db /nominal 6ohms (I would think)
Ok, meter does not exactly BOUNCE, but the does move up from its static position at 9:30 to about 11:00 when it is at it's loudest. Doesn't really seem TOO loud, but that's a matter of opinion, unless it's causing hearing damage..... Anyway spoke to the folks at Pass Labs today and they said I COULD be running out of power, maybe the X250.5 is the way to go but borrow one first and see if that changes things. Sensible, those guys. They felt that meters hitting 11:00 was close to running out of power. I was kind of surprised at that, but who'd know better than them? Anyway they also suggested a change of wire to the upper section of speaker an another way of taming any harshness, but I don't think that would really help based on other cable I have used in the system. Just as an aside I originally had a pair of Aleph Os, but I sold them for the 150.5 to get more detail and dynamics, and that was exactly what I got. Another reason for looking into the 250.5 is that there are currently 2 in NJ on the list, and that's where I am, so It'd be very simple for me to buy one of them. Thanks for the info so far guys!
Once again, I think you are running out of power in class A mode, not total power. You indicate that when you turn it up, it gets bright and grainy (my words), this is indicative of these Pass amps that transfer out of class A to class A/B, in my experience. The 250.5 isn't giving you much more power in class A. I understand your desire and goals in moving from the Aleph series to these, but I think if you want to stick with Pass, you need to step up to more power in class A, even if it is less overall power in A/B to get the results you want, louder volume without the sound falling apart while achieving the more detailed and attachs that you felt were lacking in the Aleph series (with its more tube-like sound in comparison and its SET based design).

I still wouldn't rule out the room as a contributing factor. Some rooms can handle a certain volume or SPL level and exceeding that level can have consequences that aren't as noticeable at lower listening levels.
Interesting theory about the room. You could be on the mark there as there are absorber panels between the speakers on the front wall,and a panel at each first reflection, but nothing behind the listening chair and nothing on the ceiling, although one can go to far there too. Thought the live end-dead end theory was at work, but I'll try some absorption in the back too. Also understand where you are going with the class A amps. I was thinking in terms of total power, not class A power when I thought about the 250.5. I'd probably need at least an XA 100.5 to make it work in class A, but that is WAY above budget.
I would not rule out XA60.5s being able to drive the 3As to VERY loud levels - but, still expensive.
I agree that you should look at the room. IME, some adverse room effects, particularly in the high frequencies, are inaudible at lower volumes, but quite noticeable at louder volumes or during peaks.

Here is a 10 second test: Standing in a couple different places in the room, clap your hands loudly. What does the decay sound like? Is there ringing? You may have a flutter echo that is bothersome only on peaks.

If you do have a room problem, then adding diffusion at this point may be a better idea than adding more absorption, but both should have a significant impact.

Bryon is right IME. Try diffusion on the back wall versus absorption.

Ceiling though is a nice area to address as it too is a first reflection point. But ceilings are a bit more difficult from an aesthetix stand point.
Adding to the room treatment remarks made by Bryan and Ckoffend, I might suggest you temporarilly take your side wall 1st reflection absorbers and move them to your back wall (behind the listening position); reflections from the back and front wall are more troublesome than side walls and ceiling due to the lower angles of incidence which reduces apparent source width and spaciousness.

Diffusion - either 1D or 2D - on your back wall works well depending on your sitting distance. Note that the diffusion coefficient depends on the angle of incidence of sound, with the greatest diffusion occurring at 0 degrees incidence, and because of the lower angles of incidence from your speakers to the back wall, diffusion can be very effective in helping to add "listener envelopment," a positive thing.

Many people mistakenly walk in a room, clap their hands and hear slap echoes not realizing it does not accurately represent what they hear from the loudspeakers when sitting down in their chairs. Slap/flutter echos will be most audible with short transient sounds - and probably inaudible with sustained music. Be sure to have someone stand next to or over your speaker and clap their hands while you listen from your listening chair to detect whether flutter echos can be heard there or not.

Good luck and keep us posted.
You might also look into your AC power. Is your Amp plugged into a dedicated line?
Update to the problem. As hard as it is to believe, I changed the power going to my pre-amp from a conditioner that had my digital front end plugged into it to one that only had an analog device plugged into it and the harshness was almost completely eliminated. This even though the MFR said the outlets were isolated. Then tried heavy curtains on part of back wall, but that made things too dull, so guess I'll live with the considerable improvement the conditioner switch gave me, until I can get some diffusion for the back wall and try that. Thanks to all! And keep the ideas coming.
Plug your amp right into the wall, and forget the conditioner.
I agree with Swanny. Amps directly into wall.

Ccanino, My Equitech unit has isolated and separate plugs for digital and analog and I still unplug my digital when I spin LPs.
Seems like separate is absolutely the way to go as far as power is concerned. Just wish it would be easier to get a dedicated line into the room, but there is no floor access to the main panel as there is a slab floor. Ceiling is floor to second level. Like I said though , major improvement with separate power sources!