Water Cooled Amp?

[danielwritesbac]

Originally posted by MotoMan_Yz400
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.

See attached Excel spreadsheet

[jcx]

simply using more chips, paralleled (w/small current sharing Rs) on a conventional heat sink is likely to be cheaper and less hassle

paralleled outputs give bigger current headroom for loads with impedance dips, and the multiple packages spread out the heat over the heatsink, using it more effectively and puts the unavoidable package thermal resistances in parallel as well

as I mentioned you can't beat the surface area and air flow requirements in the end

just measuring thermal resistnace is fine, but heat pipes have a max transfer rate - when you've boiled all of the fluid off of the hot end the incremental thermal resistnce skyrockets, but I believe some of the cpu coolers must be over 200 Watt capacity to do the job, this number should be on the datasheet - requires lots of power to measure yourself

[MotoMan_Yz400]

Well looking at the numbers I see that CPU finned sinks are VERY efficient. I dont know the stock specs on the average audio heat sink (according to the spread sheet above, for basically maximum output on the chip will need a sink that is 1.5 C'/W or better. Reading some specs on CPU coolers, they have ratings of 0.16 C'/W or better. And with what people say, that a low end water coolers is equal to a high end finned sink, leads me to believe that water cooling may not be a bad choice. Now fans and pumps is a worry, maybe I incorporate a small heat sink with a water cooling as a thermal backup. When you really start pushing the amp (high volumes) the pump then kicks in and adds a bit extra. I know this sounds uber complicated, and it is. But one part of DIY (atleast for me) isnt really making something that you want to have, but more the learning process. Adding bells and whistles. Building something no one else has. If I wanted the easy out, I would just go buy an amp.

But I'm still unsure exactly the route I'm going to take here, just doing some research looking for possibilities to try something different.

[Nordic]

A good PC heatsink can dissipate in the region of 60W with a good fan speed...

Is it quiet? No

Is it hell to keep the noise generated by the fan out of the circuit ? yes

Generaly I'd do anything to avoid haveing a fan running in the background...this would include watercooling....

With watercooling the only limit is what size radiator you can connect and how much air you can push through it... There is also a tower based watercooler which drops droplets back into reservoir, cooling them in th process.... but over $200.

As far as I'm concerned it is not a matter of is it possible... is more... is it practical...?

[TheMG]

Originally posted by MotoMan_Yz400

and making a custom radiator (possibly as the lid of the chassis).

Not a good idea. All you would end up with is a ridiculously expensive hot plate.

There's a reason why passive heatsinks are vertical and not horizontal: hot air rises. You want the hot air to flow along the surface of whatever you are using to dissipate the heat. A flat horizontal metal plate is not going to dissipate heat very efficiently.

There are some very nice computer water cooling radiators you can get. Some of them even fit double or triple 120mm fans. Put some low-speed fans on there and your amp will be both reasonably quiet and cool enough.

If quiet fans are not quiet enough, you could add a temperature control for the fans, so they don't kick in until needed. Maybe even incorporate a passive cooling component into the loop so the radiator fans are not needed until you really crank that thing!

[danielwritesbac]

Hot plate? Actually that is a type of passive cooler, like this:

The aluminum top plate is up on spacers, at least 3/16" not touching the sides--there's an air gap.
And there are ordinary heatsinks hanging down from the aluminum top plate (+thermal paste between join).
And there are vents underneath the ordinary heatsinks.
The heatsinks don't touch the bottom of the enclosure.

Although the contact points between heatsinks and plate are critical, if airflow path is successful, hotplate style is a mighty effective passive cooler. Moving air surface = outside area of the plate.

For the "T" chips, this big aluminum plate can be lacquered (on top and sides, not bottom) and then the chips don't require micas.

[defect9]

If you go water, here's one of the recommended pumps for both durability and low noise

http://www.dangerden.com/store/produ...&cat=23&page=1

-Jared

[camshaft]

I put together a water cooling system for my PC several years ago, all from dangerden parts. Of course it looked cool, and I was able to overclock my 2.8ghz p4 to 3.5ghz with barely any increase in cpu running temperature. In it's final configuration I was using a 15" by 5" by 1" radiator mounted externally to the back of the case.

I grew out of my water cooling phase in the end. It was great at first, but after 3 years of running 24/7 the maintenance only starts to increase. When 2 nights before a major final exam in college a plastic seam in my reservoir started to separate and leak, I decided the gains weren't worth it anymore and just switched to one of the big zalman heatsinks. Costs several times less than my water cooling system, I haven't noticed any loss in performance, and it's been running for 2 years now without being touched once.

Basically I'm just saying I don't think the long term maintenance in water cooling is worth it. It's likely that after several years when parts start becoming brittle, and you start getting the ugly mineral deposits everywhere, you'll have wished you just went with a good old heatsink from the start.

I also just want to add some info. As others have said, there are some non-water solutions or additives you can use, but none of these conduct heat as well as water. If you use water, you should use distilled as it won't have minerals as others said. However, the water will still leach minerals off of the insides of the metal in your cooling path anyway though, so it will still just be a matter of time before everything gets a coating of mineral deposits.

Austin

[TheMG]

Just fill your entire amp chassis with oil.

[MikeHunt79]

Originally posted by TheMG
Just fill your entire amp chassis with oil.

This guy done it with his PC, and even cooked some chips (fries) while playing a game.


http://duggmirror.com/hardware/Photo...Fried_w_Fries/