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Pass labs X250.5 cracking noise

Hi all, recently bought a used X250.5 from a dealer on audiogon. Really happy with the SQ. The amp makes a crackling noise after powering down. Its a few cracks/pops - very intermittent and then it subsides. Spoke with Pass engineer and he assured me that the noise was coming from thermal contraction of heat sinks etc after normal operation. This weekend I noticed that the amp made cracking noise during warm up too. Again this is one or two and then after the amp warms up - i dont hear any more pops. Or i guess the sound from speaker masks it perhaps? I did pause music and noticed the amp for about 30 minutes and no cracking/popping noise during that period. Anything I should be worried about? I'll call Pass again this week - but wanted to see if there were any thoughts?
pistha
kosst_amojan
2,095 posts
 
My build of the F5 runs between 155F to 160F and that thing is making pinging sounds 10 minutes after you turn it on. 

The amp cools itself be convection draft. If one side is close enough to something to alter the natural flow of convection you'll have one side run warmer. 
lacaed
1 posts
 
I've owned the 250.5 and the xa series.  They both made cool down noises although the xa noises are louder and it makes more of them.  Bigger heatsinks I'd guess.  
instlouis's avatar
instlouis
47 posts
 
My 250.5's always seem to "clink" when going from standby . Under normal listening 65-72db they will get to 53C ( 127F) . Putting them back into standby after a good session they will " clink" again once as they cool down. I have always thought it was heatsink expansion/contraction.  It's never been a concern. 

@mickeyb - Pass Labs does NOT feed anyone BS.  Nelson Pass would never allow it. They listen and respond professionally and always have which is why theirs and many high end equipment manufacturers maintain their users respect and loyalty. 

Shad
cal3713's avatar
cal3713
388 posts
 
Yep, mine did this too.
ozzy's avatar
ozzy
3,650 posts
 
I owned the X350.5 and X350.8 and both exhibited the cracking sound as you described. Too me it was more of a clink sound.
Its normal because the high heat that these units generate causes the metal casing / heatsinks to expand and contract. 

ozzy
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