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Pass Labs heatsinks temperature

Hi all

I have Pass Labs xa60.5 monoblocks and they are always warm to the touch at the heatsinks and not as hot as other class A amps I'm familiar with. A friend from the US that has the same model visited my place and told me his amps ran very much hotter than mine. I got concerned and looked at the manual where temperature was estimated at 55 degrees Celsius. I estimate mine at around 40 Degrees. I'm concerned my amps are not biased to pure class A as they should be. I contacted Pass and while they repeated that heat should be around 55 deg. they had no idea if my concerns are valid and they sounded quite mysterious about it. Did anyone has a xa.5 series model ever measured its temperature or has an idea what can I measure without opening the amps (with a technician) that will prove that they are working only in pure class A ?
Thanks in advance
icorem
rtn1
535 posts
 
Mine measure 150-152 degrees at the heatsink midway down its length. After 6 seconds, a touch definitely becomes quite uncomfortable. It is the same between the 2 amps. The heatsinks at the front and back are around 140 degrees.
jdoris
972 posts
 
Your 200.5s are a lot more amp than some being discussed here, Rtn. Could that be a factor in heat output?

John
magfan
1,583 posts
 
All this temp measurement stuff has me thinking.
It is important in trying to get comparable data to take the data the same way using the same warm up procedures in the same location.
Sticking a baby thermometer up agains the fins is not the best technique. At work we measured hot chuck temperatures using a temp 'Puck'. A flat sensor connected by cable to a handheld device.
Some FLUKE meters can use a thermocouple, too. You just need the right 'type' so MV ouput matches the appropriate temp readout. A 'Type T' may be just the ticket.
johngp
225 posts
 
I am not using a baby thermometer, using an infrared. I've checked the temps up and down, front to back and all the different fins and the highest I got was the 119.8F. It's warm but not hot to the touch. I'm going to run them all day today and then check again just out of curiosity(sp?).
magfan
1,583 posts
 
John,
Good. Now if others use similar equipment with similar competence, the data could be compared.
As it lies? Well, 3 or 4 others have measured, with unknown means and accuracy, while getting results which confuse me.
No relation to bias condition has been stated, though all are on 'a' amps.

I've read, on the Pass DIY site the bias setting procedure for a Pass designed amp, and it was thorough enough that I have trouble believing an amp could leave the Pass factory and be mis-biased.
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