Pass Labs 350.5 or 600.5 owners--breakin time.....

I just bought a pair of Pass Labs 600.5 monoblocks which now have about 25 hours playing time on them. They are starting to finally open up in the upper registers and in detail. Still kind of veiled though... They sound better after 4+ hours of play. Could anyone comment on the total breakin time and what they may sound like after say 100 hours? Thanks! Stan
I had a 350 & now the 350.5. They both took 250 to 300 hours. The .5 was the shorter of the 2. In my experience they take you on a bit of a roller coaster ride, great one day, bad the next until the break in. But they will in time. Be patient.
I agree with HiFiguy, the relationship is a little rocky in the beginning, but after about 300 hrs they sing sweet like a bird. Well worth the wait.
i found the same. it took abour 300 hrs. for my 600.5's to really break in. its tough but be patient, it is well worth the wait.

Talon4, I have had the 350.5 and now run my system with XA-100's, both took about 200 to 250 hours to reach burn-in, after that there is a slow process of change towards their final performance signature. I would love to hear your final opinion regarding your 600.5's, I believe that Nelson Pass and his crew really "nailed it" with the .5 and XA series amps.
Thanks for all your responses! I'm just wondering what kind of time I'm looking at and the stages of change, which is fascinating. I'm looking forward to the final system sound though. Each monoblock is massive (21x19x11.5) and weighs 150 pounds. A friend was going to help me put them into the system, but I didn't want to wait. I put them on their amp stands myself. I'm glad I didn't blow out a disc in my back. Next time I'll wait for some help. The amps on their amp stands make my Egglestonworks Andra 2's look smaller than before... Pass Labs also rebuilt my X 0.2 preamp, which I bought used from a dealer about 8 months ago... new volume pot, new power supplies, plus alot more... no charge! Very nice people! Thnaks Pass Labs!!! I love hearing about the .5 amps. Very few actual reviews on the 600.5's... Thanks again guys!... Almost forgot--my wife likes the looks of the amps. She says "the blue lights look cool". So the WAF is good. A big plus.
My experience is a little different. I've found that most Pass amps level out after about 100 hours of use once the caps are fully broken in. The XA series take a little longer perhaps 150 hours total. I've not noticed much change after that. Do not be shy about pushing them if matrimonial harmony permits.

I recommend leaving the amps powered up 24/7 but in standby mode when not listening. Exceptions are vacations, thunderstorms, visiting nosey children, etc.

Disclaimer, I sell Pass products.
Hello, I've waited a while to make sure of my findings... My Pass Labs 600.5 amps now have about 900 hours on them. At 650 hours the amps started to became more musical, clear, detailed, layered and 3 dimensional. It took another 100 hours more after that for the changes to be permanent. Since the amps haven't changed for 150 hours now, I would say about 750 hours for full breakin, probably due to the large power supply of each amp. Take care. Stan
Thanks for the reply Stan. My XA160s now have about 75 hours on them. I am hoping they do not need 750 hours??? Just out of curiosity, do you yuse aftermarkets power cables with your pass amps?
Hi Tboooe, At about 300 hours on the amps, I tried a Shunyata Anaconda Alpha Helix on each amp-(borrowed from the Cable Company).The Anacondas made the bass fuller with more bass "sustain" and detail, helped the mids somewhat in clarity and musicality, but rolled off the highs. The highs were already slightly rolled off at that point, due to breakin. I'm using the stock power cords right now, but I want to try a pair of Anacondas again to see how the amps perform in the upper frequencies now that they are broken in. It may be a pretty good match. Best wishes. Stan