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Old 4th March 2011, 10:29 PM   #1
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Default Think this will be a big enough heatsink?

Hi,

This is probably amongst the most asked questions for chipamps and I guess I'm no exception. I'm building an LM3886 amp as some of you may already know. The only thing I have not ordered is the heatsinks/enclosure. I think I'm going to use a wooden case for a couple reasons, however, I still need some decent heatsinks.

I'm planning on driving about 35W (Max!) per channel, but 15-20W/channel would be more ideal.

So I bought one of these back in the day: Ultimate CPU Cooling Solutions! USA

I bought it for the mosfets on my motherboard but it wound up not fitting unfortunately. Since they are still being produced and run for about $12 each, I was wondering if anybody had any thoughts on how well it will keep the chipamps cool. The dimensions are 64mm (2.5") x 12mm (0.5") x 44mm (1.75"). Seems a little bit on the small side but it does have a copper base/heatpipe as well as a lot of soldered fins, versus just a hunk of aluminum.

There's no thermal resistance/dissipation information on the heatsink because it's meant for computer enthusiasts, not people like us.

It's pretty small but not terribly small.

Ideas?

Thanks.
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Old 5th March 2011, 06:25 AM   #2
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The LM3886's case is 20 x 17,5 mm. The flat surface of that heatsink is only 12 mm wide. You will at least need an adapter to achieve low thermal resistance between the LM3886 and the heatsink.

For worst case conditions that heatsink will probably be too small. For practical conditions it may however work, so you will just have to try. The heat dissipation depends on ambient temperature, average output power, rail voltage and load impedance and you can usually live with a much smaller heatsink than the worst case calculation specifies.
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Old 5th March 2011, 03:02 PM   #3
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Ooops. You're right.

I decided to buy two of these: Hyper 101 - Cooler Master - Leading Provider of Computer Case | Cooler | Power Supply


I have a strange addiction to computer cooling solutions. They are so pretty!

These are actually a lot smaller than they look and I've done all the measurements. The hardest part will be mounting them, but I've got that figured out too...

Should work swell. Only $15 each!
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Old 5th March 2011, 10:58 PM   #4
MunkeyQ is offline MunkeyQ  United Kingdom
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Join Date: Mar 2011
Location: Nearish to London...
Nice choice. I've got a huge box of old heatsinks for outdated CPUs, begging for an audio use...you've inspired me!

Anyway, how are you going to attach the IC? Tapping holes isn't possible due to the heatpipe embedded in it...clamps?
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Old 7th March 2011, 12:29 AM   #5
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Yeah, I'm going to try to use clips, though there seems like there might be enough room between the heatpipes to tap a hole.

I'm going to have a wooden "wall" inside the case which they will be bolted to. There will be a square hole in the wall that the base of the heatsink will go through, sort of. It's quite hard to explain, actually. When it's done, I'll have plenty of pictures. The wall will hopefully also isolate the heat.

They'll be bolted to the wood, but that will just keep them from moving around, as they will be lying down on their sides.

If I can get a clip that fits, I'll probably use that, or I could use some sort of metal band or something....or a screw. Don't have all the parts yet so this is still sort of in my head. I'm wingin it.
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Old 8th March 2011, 11:54 PM   #6
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Here's a bit of an update. Maybe some of you will be interested in using them in your own projects...Maybe...

They didn't come out as clear as I had hoped. Macro lens failed me! Or I failed my macro lens...

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Last edited by TheLaw117; 9th March 2011 at 12:03 AM.
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