Pass labs X250.5 cracking noise
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 |
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 |
