Pass labs X250.5 cracking noise
If it were an XA- model then yes having far more class-A bias on them you would expect a certain amount of expansion and contraction with warm up and cool down noises. But your’s is an X which is lower in bias than the XA, and should be getting that warm, unless you are driving it hard into difficult to drive low impedance/high -phase angle speakers. What are your speakers and do you push the amp loud? Also are the heatsink/s hot to touch after a couple of hours? Be good if you could measure the surface temp in the middle of the heatsink on both sides as they should be equal. Cheers George |
George, I dont drive them hard - I dont think i ever exceed low 80db spl. I also notice that the bias meter doesnt ever leave class A for my listening level. I drive a pair of wilson sophia 3s. I dont think the sophias swing wildly in impedance either (per wilson). I've gota be honest - dont know what a high phase angle speaker is! I'll give the temperature measurements a shot - thanks for the suggestion! Ragav |
Between 60hz and 180hz the Sophia 3’s are a hard load 3ohm with up to 50 degrees of negative phase angle (the dotted line is the -phase angel), it could make the 3ohms look like 1.5ohms to the amp. . https://www.stereophile.com/images/211Wilfig01.jpg Measure both heat sinks after a couple of hours playing normal level bass’y music. The heatsinks should never go over 60C. and that’s on the XA., the X I would expect to be less. Cheers George |
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Called Pass and the engineer assured that this was just the heat sink making the noise from thermal expansion and contraction. Apparently the heat sink can be more tightly secured with a couple of bolts behind the faceplate. btw George - i measured the temperature on the fins and they were reading 100F & 110F on left and right sides. I mentioned this on the call with Pass and they didnt think it was a wild swing. Now i know this is a minor annoyance at best - am not going to do anything but enjoy music! thanks everyone. |
btw George - i measured the temperature on the fins and they were reading 100F & 110F on left and right sides. I mentioned this on the call with Pass and they didnt think it was a wild swing.This is fine one side could be in a draft more than the other no biggie. Just wanted to make sure the bias didn’t go out of whack on one channel. I’ve had much experience with amp heat, making quite a few massive (two man lift) 150w pure Class-A amps with self contained water cooling systems. BTW: Also not having the bolts too tight can allow movement without creaking. Cheers George |
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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 |
i have recently bought a pass labs xp.30: connected to 2 different amps i hear a crackling noise from the right speaker. Either on warm up or also later. Then it may totally disappear, but when i thought it was gone (i made some more order in the cables) today i heard it again. When on muting of course the noise cant be heard. |
@fabio3181 I would just contact Pass directly. They're great even if you bought decide hand and will help you diagnose and fix. Not that I think you need another source for fixing, but the community at https://www.diyaudio.com/forums/pass-labs/ is also super knowledge and helpful. |
@tonyptony - i've moved on! the cracking noise from the x250.5 doesnt bother me any more. It only happens during the first 10 mins and then after powering down the amp. @fabio3181's problem seems to be unrelated to thermal expansion - i wouldnt expect the pass preamps to have any measurable thermal contraction/expansion. |
