2. amps-preamps
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Is my Pass amp overheating?

The amp is an XA30.5.

Yesterday I was doing some tinkering and the amp was turned off for a couple hours (unusual for me). When I was done, I sat down to listen while the amp was still cold. To my surprise, it sounded BETTER than I'd ever heard it.

The amp is Class A, so according to conventional wisdom, it needs to warm up before sounding its best. Yet it definitely sounded better BEFORE it warmed up. So I'm wondering if the amp is overheating. To test this, I took the lid off the amp. Three things happened:

1. At idle, the bias needle moved from 11 o'clock to 1 o'clock (unprecedented).

2. The cooling fins became much HOTTER (not cooler, as I would have expected).

3. The sound quality of the amp remained "improved" even after several hours.

Can someone please explain what's going on?

Thanks,
Bryon

P.S. The amp is in a closet. But I don't think that's the problem, for the following reasons: The amp is on the top shelf of an equipment rack, so there is two feet of open air above it. There is a large fan in the ceiling of the closet that sucks air and sends it through a duct to the outside of the house. So the closet stays very close to the temperature of the rest of the house. Also, I can reproduce all the effects described above with the closet door open.
bryoncunningham

Showing 1 response by duke40

duke40
1 posts
 
Hi Bryon

Thank you for posting this thread, it lead me to try something a bit different to try to achieve a similar result.

I can not remove the lid or try a fabricated one like you designed with copper mesh and aluminium (very impressive by the way)... as I have roadworks near my house causing a lot of dust & dirt in the air.

*** So I tried ... elevating my amp. ***

Aim was to improve better/cooler airflow from under the amp, thus improving the chimney effect, hopefully to achieve a similar result to you.

My amp is similar to yours , though it is an integrated, the Pass Labs INT-30A. I was in the hardware store and found 3" high door stops made of stainless steel (also 3" diameter). I purchased 4 of them for a total of $12 as an experiment. Placed under the existing feet of my amp, it increase the space under the amp from 1" to 4".

I have also noticed that the heat sinks now run hotter and a improvement in sound (it is minor, though easily heard).

Also, thank you for posting your system. I have Focal Micro Utopia Be and reading your system was one of the things that gave me confidence to try and buy a Pass Labs 30wpc Class A integrated amp a few months ago.

John
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