Breaking-in a Pass Amp

Did you audition another X150.5 in your system before buying your new amp? If so, and assuming it was broken in, that is the sound you can expect. If you did not audition one before hand, it might be difficult to know what to expect with your particular gear. I don't have any experience with the X.5 series.

I do own XA.5 amps and found that they became more effortless, smoother and more detailed after break in. They are anything but sterile and uninvolving in my system. The improvement is similar to comparing my amps right after turn on to a couple hours of warm up. My amps were demos and as I recall sounded pretty good when they first arrived. I played them for 100-200 hours before they were really well broken in and they sounded even better.

Didn't get a chance to demo before and have them on a 10-day in-home demo; no dealers within 600 miles. After only 36 hours they are already beginning to warm up, open up and relax a bit and sounding considerably better than out of the box

No suggestions, but what a nice system you will have to listen too and bring in Christmas and the New Year. Let us know when you feel the amps have broken in and are sounding palatable.

"After only 36 hours they are already beginning to warm up, open up and relax a bit and sounding considerably better than out of the box"

I think you can expect more of the same to come. That was my experience with my XA.5's.

For X250.5 told by Pass dealer; 4 days on continually, then 4 days of 16 hours on, 8 hours fully off (not standby). I also felt it improved a little more after a few weeks of regular use following the 8 day break-in.

...it's Ok but nothing exciting - good detail and opennness and very dynamic yet tonally bland, limited transparency, a bit sterile and not very involving.
What changes can I expect ..

That's the way they are. There won't be big differences but you will get used to it and after a while you will like it.

Pass doesn't do some kind of bench break-in prior to shipping ala Bryston?

Give the caps a chance to form, maybe.

"There won't be big differences but you will get used to it and after a while you will like it."

Finally! Thank you.

Thanks for all the responses and encouragement.