Pass labs x250.8 burn in

I cannot comment on the .8 but my new Pass 350 took about 150 - 175 hours. I have owned Pass designed amps for forty years. I also owned a couple pass preamps, and I have felt they are not nearly as good as their amps. They lack the rhythm and pace that his new amps have. 
 

If you want more midrange bloom and musicality, I would look at Audio Research. 

Agreed on the Pass preamps. I have owned both the XP 20 and 30 paired with his XA60.8 monos and neither of the Pass preamps could do the amp any justice. Anemic, sterile, and fairly lifeless. Pair Pass with a good tube based preamp and your ears will thank you.

leave it on for a few weeks, but for a few days in the middle, shut it off at night...this will get you 90% there...play a lot of music...this was the advice I received from Pass...for me the XP Pass preamps are excellent, much better than the original X series...currently using XP-22

I owned the Pass Labs X350.5. Reno HiFi sent me the X350.8 to try and I thought the X350.5 was livelier than the newer X350.8 version. So, I sent the X350.8 back.

At the same time, I also owned the Pass Labs X10 preamp. Again, not overwhelmed. But we all have different speakers, rooms, preferences etc.

ozzy