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Old 14th February 2008, 02:35 PM   #1
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Default Water Cooled Amp?

Has anyone tried to implement a computer water cooling system to a chip amp? I know CPUs can put out some serious heat, and people have said for very high end computer systems, to run water cooling for maximum cooling. I see when you buy a WC kit, it comes with copper pads for the CPU, could someone retro-fit these onto their amp ICs and potentially run cooler?
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Old 14th February 2008, 03:51 PM   #2
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You're late to the party, but welcome nonetheless.
Remember that silly "Did you search?" button when you started this thread? You might have tried searching.
I started the first (as far as I know) water-cooled amplifier thread here years ago and there have been a fair number of threads since--roughly one every six months or so. Going with water wasn't my first choice, but I live in a nearly Stone Age part of the country and heat sinks simply don't exist. As the expression goes, "Necessity is a mother..."
I had monoblock class A amps that needed to dissipate 300W of heat per channel and later built a second pair. That's 1200W of heat, or about the same amount put out by a hair dryer. Yikes!
The good news is that the water cooling system could not only swallow that 1200W whole, but that in real terms its cooling capacity for home audio use is essentially infinite. The gooder news (yes, I know that ain't gud English) is that it was far cheaper than an equivalent number of passive heatsinks.
The bad news is that it's not portable, but I don't lose a lot of sleep over that.
My system isn't based on CPU coolers. I don't even know that there were any commercially available at the time. I just used things that I had on hand. Since then some pretty fancy looking CPU do-dads have come on the market and I have no doubt that they can do the job.

Grey
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Old 14th February 2008, 04:43 PM   #3
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Well i know one thing everyone on here is concerned with these chip amps is heat. I'm working with the LM3886T chip, and those little suckers can really handle some power, it's just they over heat quickly. So they say 65W output, which is limited because of the heat needed to sink is just crazy. So I was figuring using those CPU coolers, (single CPU cooling pad per chip) and running water cooling. That way (hopefully) you can push them a little bit harder, just providing you can get the heat out. I guess my question is, does water cooling provide more heat loss then a standard finned heat sink? Even with a fan? I think that would mad cool to have an external heatsink with a single fan cooling my amp. But mostly I want to see what peoples reactions are. If its better performance, or even worth it.
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Old 14th February 2008, 07:40 PM   #4
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We use liquid cooling of various sorts where I work, both straight water and water and glycol mix. The cooling limitation is really only a function of your flow rate and the temperature of the water before it enters the heat exchanger that your device is mounted to. The last company I worked for used a large liquid cooling system to cool a high volume semiconductor test system. This machine used a 480vac 3 phase supply at 100 amps per phase, so you can guess that the various devices could produce some heat. These machines were used to test memory chips and microprocessors to verify that they meet spec.
The only thing I worry about with using a water based coolant is its proximity to electricity. If you can spring the money, using a nonconductive liquid like flourinert is a safer thing, but it's expensive. Alternatively, if you can keep it from getting contaminated, distilled water is not conductive, its only when it has impurities that it conducts electricity.
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Old 15th February 2008, 05:43 AM   #5
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Water cooling would probably be a good solution, but there are several problems. The first is safety, but if you have your mains side in a separate enclosure, good grounding, and good fuses this shouldn't be a problem (still, be careful). The other problem is noise - water cooling requires a pump to run the entire time. You would probably get equally good results spending the same cash on a bigger heatsink and some big, slow (120mm or bigger) fans.
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Old 15th February 2008, 05:46 AM   #6
defect9 is offline defect9  Ireland
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A few good places to get computer-based watercooling supplies that you can easily use for amp-based projects are:

Dangerden.com
Petrastechshop.com
sharkacomputers.com
sidewindercomputers.com

Also, they have non-condictive fluids available in multiple colors, and even some de-algae solutions for if you use water.

They also have peltier+water cooling solutions, if you want to go overboard

-Jared

quick, guess what one of my side jobs is?
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Old 15th February 2008, 06:17 AM   #7
jcx is offline jcx  United States
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Heat Pipe cpu coolers look way easier to apply, finding hard # for degree C/Watt, max Watt isn't easy though

these just move the heat to a fan blown fin array so you can achieve very high power density at the copper chill plate but are not "magic" when it comes to air flow, surface area and temp rise for ultimately dumping the heat into the air

also remember you can't "beat" the junction-case thermal resistance heat dissapation limit without acutally chilling the case below the 25 C "infinite" heat sink rating

and SOA current limiting inside the chipamps will limit available power with likely only modest gains for "infinite" heatsinking
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Old 15th February 2008, 10:15 AM   #8
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Even easier is the "big fan" versions of Zalman CPU coolers. That company specializes in quiet cooling. Larger fans turn more slowly--so its like much less noise than a water pump's nonstop throbbing growl.

Also, LM3875T, no detectable difference in decibels, but less heat output.
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Old 15th February 2008, 01:25 PM   #9
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Quote:
Originally posted by jcx
Heat Pipe cpu coolers look way easier to apply, finding hard # for degree C/Watt, max Watt isn't easy though
You can find it experimentally -- I use a screw mounting Dale 50 watt resistor with silicone grease -- put enough current through it to draw 10 watts -- I attach a thermometer to the heat sink, measure ambient temperature and the temperature about 10 minutes later. Air flow should be unobstructed and still. Just measure the temperature gradiant and le voila.

Ive mentioned this article before -- the "Stanley Steamer" was a ham radio 2 kW amplifier described in QST in the 1960's.
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Old 15th February 2008, 03:39 PM   #10
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Quote:
Originally posted by jcx
Heat Pipe cpu coolers look way easier to apply...
Yeah I was thinking that. However I'm going stereo in one chassis, and I'm going to have 4 chips per channel (maybe more later). For some reason I see computer cooling devices as ALOT more efficient source of cooling than standard audio heat sinks. I'm going to be putting alot of power in a small case, I really dont have the room nor budget to put 8+ CPU heat sinks in the case. So I was thinking of using CPU water cooling pads, one for each IC, and making a custom radiator (possibly as the lid of the chassis).


Quote:
Originally posted by danielwritesbac
...Also, LM3875T, no detectable difference in decibels, but less heat output.
What do you mean by that? Whats the difference between the LM3875T and the LM3886T? They both are a single mono amps non insulated right? They look as if to have the same specs.
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