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Old 14th September 2001, 10:14 PM   #1
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Hi All,

I was just looking at Tom's Hardware page http://www.tomshardware.com/ where they describe a DIY CPU water cooler. With the power levels involved in modern Class A amps, esp Single ended designs, and the problems associated with getting rid of that heat, what are peoples thoughts on water cooling.

With the design described, the pump and radiator could be located a long distance from the amp, thus elminiating any problem with pump and fan noise (Radiator inside for winter, outside for summer). The size of the enclosures could be dramatically reduced with the heatsinks eliminated, and with regards to portability, self sealing, quick release connectors may be used so the tubes containing the coolant may be diconnected quickly and without spillage.

The other option for those who are not billed by the amount of water they use, the water supply could go straight to the amp, and then to the drain, eliminating the need for the pump and the radiator.

Has anybody experiemented with water cooling. I'm especially interested in making it as socially accpetable as possible (i.e. as invisible and unnoticed as possible)

Thanks, Adrian
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Old 14th September 2001, 10:45 PM   #2
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This topic has come up in the past. One of the best examples is 'Water cooled audio circuitry'. I'm sure that other threads can be found with the 'search' feature of this web site (Thanks Jason).

Grey did a good job documenting what he had done, and there are several ideas from other people in the thread. Personally, I'd like to use a different liquid (Flourinert), but water is the only functional, inexpensive, alternative.

I have personal experience with large (over 100KW) liquid-cooled computers (including liquid immersion), and I can tell you that it's a hassle. You have to consider such things as corrosion, bacteria growth, evaporation and expansion/contraction of coolant. This doesn't include such things as filters and flow control valves. Also, fault detection should be included, or your amp will SMOKE when the pump fails, or a hose breaks.

On the scale that's required to cool an amp for your house, most of the above issues become smaller, but they never go away. There are simple solutions for most of them, but you have to recognize that the problem exists, or you'll never look for the solution.

Good luck.
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Old 15th September 2001, 02:20 AM   #3
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I am just starting up building a pair of Pass Aleph 1.2's and have thought about the exact same thing. Water cooling is really the most eficient way to get rid of heat. I have also thought of Peletier cooling devices as well but after weighing all aspects of things a large heatsink is still really the practical way to go plus it looks better if the right(designer type sinks are used. With water there is always the chance of water leaking and one HAS to use de-ionized/distilled water to cool with other wise a scum buildup will occur. Other things such as keeping water level topped off and cleaning the cooling system are a reality.
I work with high wattage Xenon lamps and projectors that are water cooled and for these it HAS to be de-ionized/distilled water...nothing else and it has to be extremely pure.
With Peletiers you always will have moisture buildup and some method has to be sought up to deal with the moisture problem other wise you'll have a corrosion problem. Overall, Peletiers were a pretty big failure for CPU cooling.
Mark Gulbrandsen
Salt Lake City, UT
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Old 15th September 2001, 09:08 AM   #4
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The problem with Peltiers is the same as any active cooling system. All it really does is move the heat around, adding to it in the process. Water cooling is the active cooling method that adds the second least amount of heat (the power into the pump; usually 10-20W). Forced air cooling (low speed) adds the least (power for the fan motor; 2-5W), but it's harder to get a quiet fan than it is to get a quiet water pump.

Peltiers are very limited in the way they can function. They are limited in the number of watts they can transfer, and the temperature difference between the two sides. If properly controlled, they can be used to cool CPUs, but they dump still more heat into the case. This is, in my opinion, a net loss.

Using a Peltier to cool an amp makes no sense. You'd need at least 2 large units in parallel for a ZEN (8-10 for a big Aleph). The power drawn by this is VERY high (1x-2x power moved), and would have to be disipated by the heat sink, along with the initial power (from the amp). Also, you'd have to closely monitor the 'cold' side of the Peltier. If it gets too cold, you'd have to shut down the Peltier (condensation is BAD for electronics). If it gets too hot (Peltier failure), you'd have to shut down the amp. NOTE: Peltiers seem to be less reliable than amplifiers.

If you have room, and can stand the heat, plain old heatsinks are still the best way to cool an amp. If you can move the amp into a remote location (like a closet with ventilation), forced air cooling will work. Otherwise, liquid cooled is the only acceptable way left.

There are chemicals that can be used to keep growth down, reduce corrosion and increase the acceptable heat range. The most common is plain old anti-freeze (50/50 mix with tap water). You'd be suprised at how much heat a truck radiator can disipate, even without a fan.
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Old 15th September 2001, 11:26 PM   #5
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My Alephs are still water-cooled and running like champs.
No, you need not use de-ionized water. No, you need not top the system off if it's a closed system. I've been going for six months or so, and loving evey minute of it.
So far, I'm still running without forced air on the heat exchanger, but as I'm assembling a second pair of Alephs and plan on using the same water-cooled system, I anticipate that I'll need to install a fan once the second pair is operational.

Grey
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Old 15th September 2001, 11:56 PM   #6
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In the motion picture industry where we use water cooling on large xenon lamps the Xenon lamp manufacturer specifies that one has to use de-ionized/distilled water to keep the lamp warranty valid and to eliminate the possibility of a mineral scum form forming in the cooling circuit. This is a very common procedure in Imax and several 8 perf 70mm projection systems. It is also done in high power UHF TV transmitters as well where any buildup of scum would only lessen the cooling efficiency. Once a scum forms it is really hard to get rid of it. I have seen countless 35 and 70mm projectors film gates that had plugged cooling circuits from not using at least distilled water. In normal projector operations I reccommend using 50% distilled water and 50% antifreze. Not only does this make the cooling more effficient,it eliminates stuff growing in the water. It however only delays the formation of scum but it does not eliminate, or stop it completely. So perhaps you understand that if I did a cooling system it would use de-ionized/distilled water only...same as an Imax pojection system uses. Over the long haul there would be no problems at all. I'd love to see pics of your water cooled amp.
Mark Gulbrandsen
Salt Lake City, UT
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Old 16th September 2001, 03:46 AM   #7
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Grey:

have you thought about improving the performance of your cooler by adding a "wetting" agent similar to the automobile radiator performance additives you can buy at Pep Boys etc.? The performance boost for cars is claimed to be significant...
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Old 16th September 2001, 03:48 AM   #8
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actually, i've been thinking about water cooling an amp of my own, and it just occurred to me after that last post that perhaps an old car radiator could be a cheap solution. hmm... i'll have to go back and re-read that old thread.
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Old 16th September 2001, 11:13 PM   #9
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Default re: Water cooling


Another option might be to use forced-air cooling with the fan sitting outside the room where the amp is located and 'pressurized' air is supplied thru some hosing to the bottom of the heatsinks [eg make a small box under the shelf the amp is sitting on and make a slit in the shelf in the position of the heaksinks] and so support the normal convection. I have no figures available about the reduction in R<sub>th</sub>.

It is 'less' critical than water cooling in a sense that no things have to be 'water tight'. In case of failure of the fan, failure of the amp will occur depending on the 'normal' R<sub>th</sub>.

Jos
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Old 17th September 2001, 01:55 AM   #10
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Mark,
Since other peoples' approaches to water-cooled systems may differ, I can't speak for everyone, but my system--with a single pair of Aleph 2s on it--only runs about 105 degrees or so, maybe less. I don't remember exactly, but it'll be in the Water Cooled thread. The point being, that's less than the temperature of hot water coming out of a tap. Tepid water just isn't subject to a lot of precipitation of calcium salts, etc. Antifreeze isn't necessary because I don't need to keep the water from boiling, and the metal parts of the system are all copper, which is quite stable in the presence of water, else houses wouldn't have 50 year-old copper water pipes. Someone with a system that runs hotter or needs corrosion protection might need to consider the use of antifreeze, but I don't see any benefits--only negatives.
C. Simpson,
I haven't looked into any additives because the system runs very cool as it is. I suppose you could argue that it might be nice to get it down a degree or two more, but it's already running at or below the temperature of my old Thresholds. If, after hooking up a second pair of Alephs (or possibly a SOZ variation), I discover that I've run past the cooling capability of the system as it is, the next thing I'll do is add a fan to the heat exchanger. So far, I'm still running passive convective cooling there.
Jos,
The idea of running air in from another room (or even a cool basement) has been tossed about before, possibly in the Water Cooled thread, possibly somewhere else. I think it's a good idea, myself. My problem was that I couldn't find big heatsinks for any reasonable sum of money, and I was determined to run the outputs as cool as possible. Unfortunately, not having heatsinks, there wasn't anything to blow air past. Perhaps someone will discover a cheap, reliable source of big heatsinks so I can go air-cooled. Until then, I'll keep fiddling with the water-cooled thing. I just did it as an experiment. It worked even better than I expected, so I'll stay with it for the time being.

Grey
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