Where to buy heatsinks

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I too had this problem, in the end I stooped for the Farnell IMI Marston extruded ones.

Anybody thought of or tried any really different designs for heatsinks? I'm thinking water cooling or the like! Would be interested in pic's of any such implementations.

Oh, the IMI Marston cold cubes look quite good, (good degC/W/£or$), although it may be quite a bit of effort to keep the required fans quiet).
Funny you should mention water cooling...
I mentioned in another post elsewhere that I'm in the process of building a modified Aleph 2 and that I had something odd planned for the heatsinks. Water is what I've got in mind. I've got a length of the 2x4" rectangular extruded aluminum like you see framing windows and doors which I will be cutting down to four lengths--one for each bank of each channel. The trick, of course, will be to seal off the ends decently. For taps, I plan on NPT brass barbs tapped into the aluminum. I have a pump on hand that I use when brewing (RIMS system, if anyone out there is a brewer...), and being an incorrigable pack rat I have the heat exchanger out of a heat pump on hand. No reason a radiator out of an old Chevy wouldn't do as well or better, this just happens to be what I have 'in stock' in my junk box.
Brief discussion on attributes (all hypothetical at this point, as I'm still matching gain devices).
Advantages: Given enough line, I can put the heat anywhere I want: in the same room, in the next room, the basement, even outside. Also, there's no real limit to how much heat you can dissipate, just scale the system up and down--or, more elegantly, run the pump up and down. The pump was moderately expensive (food grade), but that would not be neccesary for someone starting from scratch. The aluminum extrusion wasn't expensive, either. Overall, it should be comparatively cheap compared to buying heatsinks.
Disadvantages: Huge amount of thermal mass. It'll take this sucker about ten years to reach thermal equilibrium. The easiest way to get around this will be to set up a thermostatic control to vary the water flow (same concept as the thermostat on a car engine--get up to nominal operating temperature more quickly). There is the possibility of mechanical noise from the water flow. The pump is an impeller type, so it shouldn't produce gross ripples that throb through the heatsinks, but there could be other things. And...holy mackeral, what if you develop a leak? Not a system you should consider if you have a puppy who likes to chew on things!
I am open to ideas, particularly on sealing the ends. I have two different ideas in mind, but don't yet know whether either will pan out. Unless someone's a masochist, let me play point on this one. You can learn from my mistakes.
SteveH: Have you considered visiting your local junkyard? The ones here sell aluminum by pound weight, and you don't have to pay postage on having all those heavy critters shipped in from Nebraska or wherever. I once saw two (yes, two, good for a stereo pair) heatsinks about 18" by 36" in an industrial power controller. The bad news...they'd been dropped together by the forklift and both had crushed fins. Curses! Anyway, the prices are good (that Al extrusion mentioned above was $6), although it's a matter of luck as to what shows up.
Jason: Thanks for putting previous postings back in the reply window. It makes it easier.

Watercooling, computer surplus and sheet cooling

Watercooling "hot ends" can be bought from http://www.aavid.com or http://www.fischer.de. Aavid have coolcat which is software to go with it ...

I too have been thinking about the radiator solution. Way to go! I have seen it on a Japanese site (amp built into speakers, more of a hot-end physical volume thing).

I just bough 27 nice (in that they were transverese + slotted + rippled + black) Pentium II heatsinks. I plan to strip off the fan and fix them to my box.

If you put sheets of alu with spacers, you can build your own heatsink very easily, especially if you place them on top of the whole deal as a "lid" and have a low power centrifugal fan running at nearly zero revs in the case (or holes on bottom + 2" feet.
I've seen bent aluminum heatsinks (Ham radio operators have been doing it for years). For small amounts of heat they work well and you can custom fit the metal into bizarre shapes that will fit between components on a board. My problem with the idea of stacking multiples together is the unpredictability of heat transfer between adjacent pieces. I was never able to convince myself that I'd be able to get a tight enough fit. So then what do you do? Smear heatsink grease on each and every piece? That's going to get expensive, fast. I've got some .040" Al 'in stock' but have never used it for anything other than small sinks for that reason.

Guys - Thanks for the info - but I don't think I will be getting into water cooling - a bit too esoteric.

Grey - I have just checked my local junk yard - they have lots of scrap aluminum, but nothing with fins.. so I have to look elsewhere. I'm not prepared to spend a bezillion bucks on new extruded stuff from Wakefield or Aavid - much as I would like to have it.

I am trying to keep the cost of making a Zen down as much as possible. I plan to mount is right inside my speaker with the fins on the back of the box.

I was hoping more for resources I could order from off the net. Please let me know if you know of any good suppliers.
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Home-made heat sinks

My brother is a machinist. He's been doing metal work for years. I showed him the plans for a home made chassis and heat sink and he said he can do that kind of work in his sleep. I'm going to have him make me 2 large heatsinks (2"x6"x15"). He said that he can get the materials from a an aluminum supplier.

If any of you guys are interested, he'd be willing to do something to your specs. He said he'd just need to get a materials/job estimate. You can email me if you are interested.

Machining heatsinks (as opposed to extruding them) is going to take a whopping big slab of metal to start with. Sounds like it could get expensive to buy that big a block.
That said...I'm salivating. I imagine that your brother just unwittingly went into machining heatsinks full time. He may rue the day he made you that offer...

instead of a solid block

One thing I considered since I have access to a mill is bying 1/2 thick flat stock and milling in 1/8" pockets for fins. Then place the whole thing with fins installed in the oven (cut to appropriate legths of course)at say 450 for half an hour then place on the hot stove to fill any gaps with solder. Assuming the fins and pockets are roughened this should provide a good joint with decent thermal properties. 1/2"X8"X36" $80 from Mcmaster carr and $40-$60 worth of 1/8"X2"X36" flat stock to be cut into fins, $10-15$ worth of solder and access to a mill for hours at a time. I decided to go the surplus route and I will have to add heat sinks as my experiments require. Though I'm sure it would still be cheaper than buying a 2.5"X8"X36 slab of aluminum.


It may be a simple task but it will also be a tedius one without cnc.
Hi there,

Check out R-Theta. They have a wide selection of extruded heatsinks and decent prices in Canadian dollars (so even more decent in US$).

You can choose the finish (black anodized or no finish). You can buy small quantity, pay credit card and you get them usually within two weeks. Not bad for catalog items cut to your dimensions.

I just bought a pair and I am extremely satisfy with the product and the service.

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My brother Lou said he could do just about anything, except extruded heat sinks. He may even be able to get anodizied material. He can get better prices then most people because he works for a machine co. and he know aluminum distributors. He would do it on a milling machine and drill press. 3 hours tops he said.

I will have him make me a set for my amp. I have a web page I'm working on. When it's up, I'll let you guys know.


[Edited by vdi_nenna on 03-06-2001 at 12:29 PM]
big heatsinks

The original Windscale nuclear reactor was air-cooled. This makes me wonder whether we need to resort to water cooling for amps running off the domestic mains supply...

One possibilty, free from potential water leaks, is to use finned heatsinks in conjunction with car radiator fans with a raised supply voltage of 24v or 36v. With *extremely* powerful fans it is possible to get about eight times the effectiveness of free convection cooling. A really big heatsink is around 0.4C/W in free air, so we can realise about 0.05C/W with this method. This is sufficient for about 1000 watts of dissipation per heatsink if running transistors at a reasonable temperature.

Nick Sheldon
Well, yes, fans work quite nicely for augmenting the basic convection heatsink, however...
There's this little tiny problem called noise. Fans work well for pro gear (Jan, this is your cue to drop in and back me up) where the dB level is consistently in the 3-digit category, but not so well for home use where the ambient noise level is much, much lower.
I've got a box full of various sorts & sizes of boxer fans. I used to hook two of them in series so they'd run slower (hence quieter), but even that gets annoying if the fans are in the same room.
N.B.: I haven't gotten far enough on the water-cooled idea to see how much incidental noise I pick up. It may not pan out. The pump will be in another room, so the only fear I have at this point is that there will be a throbbing through the lines. Unlikely, but possible. I have a few ideas in mind as to how to handle that, should it become a problem.
Re: Cooling towers. I believe at least some of those designs sprayed water on the heat exchangers so as to have it evaporate and help the cooling along. I'd rather keep the water contained than turn my listening room into a sauna. Of course, maybe there's a benefit there I ought to consider...

Not good at plumbing!


The main reason I prefer air-cooled heatsinks is because they do not leak embarrassingly all over the floor in front of my students! I am very bad at plumbing, and had a really spectacular flood once with a powerful pump and an imperfect seal.

The fan noise problem is not an issue for me personally, as I now contend with powers of over 10kw even with squalid-state amps (valve bias creeping in here). However, a friend (ex-Marconi) reports that multi-megawatt transmitters which use water cooling are astonishingly quiet.

I think another aspect which appeals is the impressive 8-fold degree of improvement one can get over natural convection with such simple, cheap equipment, albeit powerful, over-run cheap equipment. However, this has to be compared with a 23-fold improvement if you simply *stand* the heatsink in a large tank of water. Of course this relies on the thermal inertia of the water, and is not for continuous use.

Nick Sheldon
Now you're raining on my parade...I was just starting to get into the idea of a combined sauna/listening room.
Mind you, I may still end up going with air-cooled, but as I think I put above, water-cooled will allow me to direct the heat elsewhere. It will also be much cheaper, considering how much heatsinks would cost in order to dissipate the heat from a decent-sized class A amp. So far, I've got a whopping $6.00 invested in the water-cooled idea, albeit with a fair number of things I'll be pulling from the junkbox. I anticipate spending another $10-20 on pieces-parts to pull it all together, and will report back to you folks when I have results, either positive or negative.
With luck, I'll be able to pull the operating temperature down to something much lower than the 120 degree range. I'm shooting for 90-100 degrees. Obviously, I could make ice crystals form on the output devices if I tried hard enough (and spent enough money), but I can try the water-cooled idea for a comparatively small amount of money. Fallback position is, of course, air-cooled.
...I can't honestly say that I enjoy plumbing, per se, but I've done enough of it that I can generally get good results. Let's just hope that this isn't the time I end up with egg on my face...

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