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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
elberoth2's avatar
elberoth2
1,223 posts
 
Icorem - I though you are from the US. If you are from Israel, sending them back for sth as trivial as biasing, would be a total waste of money and effort. Just take the amps to your local tech, or ask one to come over.

Here is XA-30.5 bias procedure for reference purposes only - it is really easy !

(pls note that you need XA-60.5 biasing manual to perform this task on your amps !)

1) Measuring across test points adjust bias for each channel to 125mV. Pay attention to DCO across the two speaker terminals and from each terminal to ground, aim for as close to zero as possible. (P1 and P2 on the socket mounted module adjust offset.)

2)Replace cover allow unit to warm up to 53 degrees C at the heatsink, which wil take a couple hours.

3)Final adjust which will take several attempts with time lapse to allow For stabilization of temperature, and bias which tracks temp as a NTC.

4)Target Bias is 135 mV, again paying attention to DCO, absolute and differential

PS. From what I remeber, I needed 4 Digital Multimeters (you can get the cheapest one you could fing from ebay - no name ones are ~ $10 each) to perform biasing on my XA-30.5:

- one to measure DCO across the two speaker terminals
- one to masure DCO from each terminal to ground
- one for each of two bias test points (A nad B)
james123
61 posts
 
Hi. Im not sure if this helps at all, but i have a pass xa30.5 and it just gets warm to the touch. After an hour or so the whole thing is warm, certainly not hot. even the whole thick metal front panel is warm as well as the fins. im no expert on amplifiers, but it seems fine and has always reached that temperature since the day i acquired it five years ago.
i observe that the sound quality is not optimal until it is warm. i would be very cautious about opening a piece of kit like that. i wouldnt attempt it.
regards.
map
25 posts
 
I have had two XA30.5 amps and I can/could keep my hands
on the heatsinks for as long as I want/wanted. Not sure
what temperature they actually get/got to, but it definitely
is not as hot as advertised. My hot water heater is set
to around 120F and our hot water is much hotter (by the time
it gets to a faucet).
jdoris
972 posts
 
I've had the same experience with James 123 and Map with my Pass INT-30A: warm to touch (including the beefy face plate), but not hot.

John
johngp's avatar
johngp
226 posts
 
This thread got me a little curious so last night I measured the temp on the cooling fins on both of my amps(XA-100.5's). I could find no area that was over 119.8F, the amps have been in stand-by mode for several days and had been fully on and running for several hours. Not sure if this will help but thought I'd toss it in the mix.
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