Heatsinks for your poweramp

[ApexJr.]

If your intereted in HEATSINKS I have some in stock..

www.apexjr.com/Sinks.htm

Steve @ Apex Jr.

[joecool85]

If your intereted in HEATSINKS I have some in stock..

www.apexjr.com/Sinks.htm

Steve @ Apex Jr.

It's been a year and I finally revisit the thread lol.  Those sinks you have looks great, cheap and perfect for a ~50-60w amp.

[mad hatter]

I use an Ampeg SS-150 guitar head.  It has a pretty big heatsink on the back and a thermal overload cut off sensor on the inside part of the heatsink by the poweramp transistors.

I put a liquid crystal thermometer on the back and the hottest the heatsink's gotten is around 100-110 degrees F - about 30-40 degrees higher than the ambient temp.  I decided to buy a DC brushless fan from radioshack.  I attached it to a plastic clamp (plastic - so it doesn't mess up the tolex), clamped it on the amp, and aimed it at the heatsink/transformer.

It keeps my amp much cooler, only about 10-15 degrees higher than the ambient temp.

The fan does not add any hum or noise whatsoever to my signal.  You can hear the airflow slighlty if you are not playing anything, but you can't hear it whan you play and a SM57 doesn't pick it up when I mic my cab.

[joecool85]

I use an Ampeg SS-150 guitar head.  It has a pretty big heatsink on the back and a thermal overload cut off sensor on the inside part of the heatsink by the poweramp transistors.

I put a liquid crystal thermometer on the back and the hottest the heatsink's gotten is around 100-110 degrees F - about 30-40 degrees higher than the ambient temp.  I decided to buy a DC brushless fan from radioshack.  I attached it to a plastic clamp (plastic - so it doesn't mess up the tolex), clamped it on the amp, and aimed it at the heatsink/transformer.

It keeps my amp much cooler, only about 10-15 degrees higher than the ambient temp.

The fan does not add any hum or noise whatsoever to my signal.  You can hear the airflow slighlty if you are not playing anything, but you can't hear it whan you play and a SM57 doesn't pick it up when I mic my cab.

That sounds about right for how much cooler it is with a fan.  But out of curiosity, if it's only gotten up to 110 F, why did you bother with a fan?

[mad hatter]

just for the hell of it.  I was curious how much of an effect it would have and if it would add any noise.  Since it didn't add any noise & isn't hurting anything, I decided to keep it.

Plus, I figured it would come in handy if I ever played at a show at the local all-ages venue.  Their AC is pathetic and it's so hot and humid that the water condenses on the floor.  I figured a fan would come in handy there.  My amp is really important to me; it's not just an "amp".  I want it to last as long as I last.

[mad hatter]

I just thought of this.  I don't have alot of technical knowledge, so please forgive my ignorance.  It seem to me that the heatsink transfers heat from a surplus of heat to an area of lower heat.  So does this mean if you were playing in a room that was 300 degrees F, the heatsink would have the opposite effect and take the heat from the air and then heat up the defecit of heat (the componets inside) until the amp reached equilibrium with the room?

[joecool85]

I just thought of this.  I don't have alot of technical knowledge, so please forgive my ignorance.  It seem to me that the heatsink transfers heat from a surplus of heat to an area of lower heat.  So does this mean if you were playing in a room that was 300 degrees F, the heatsink would have the opposite effect and take the heat from the air and then heat up the defecit of heat (the componets inside) until the amp reached equilibrium with the room?

In theory, yes.  Luckily the chips operating temp is FAR more than what any room you would play in will be close to.

[J M Fahey]

Heatsinks are great, but they have one problem: beyond a certain power level they use too much space, and, as Teemuk pointed, the fins have to be vertical for proper convection cooling, which also limits the size. Most of them are aluminum extrusions, and, obviously, the fins must be along the extrusion axis. You can get them as long as you want (I can buy them in up to 6 meter lengths directly from the factory) but the widh is limited to around 16 cm maximum. I have seen US made heatsinks up to 25 cm wide, they were VERY expensive. The hydraulic press and dies used must be monstrous.  For me, the breaking ($$$$) point is 100/200 Watts RMS. For 50/60 W amps: just the 2mm aluminum backpanel; for 100W: 2 mm backpanel and ventilation slots in the cabinet or 115Hx50V mm heatsink with 20 18 mm vertical fins (small and very efficient), this one is *externally* attached to the aluminum backpanel . For 200W: two heatsinks as before. For 300W: a larger backpanel (500x200 mm), with 2 folded ribs reducing the apparent height to 160 mm AND a PC power supply fan (quite silent). It works far cooler (read: safer) than any of the passively cooled ones AND the transformer gets cooler too (very important in amps that work many hours non-stop).  For 600/1000W: big horizontal heatsinks, dual-fan cooled (relatively noisy 220V units, 2/4 times more powerful than 12V PC fans).  The fans pull air from the front or sides  and blow hot air to the back. In theaters and stadiums, nobody hears them.                   

[Enzo]

One source of cheap heatsinks is dead stereo receivers.  America is full of them, and they don't usually cost anything.

Much commercial heat sink material is straight extrusion, but I have been seeing in these commercial stereo receivers what I call "shaved" fins.  Instead of extruding the fins, the heatsink is more of a block of aluminum, then every centimeter or so there is a fin shaved from the block.  Imagine a piece of wood and a chisel.  You push the chisel along the wood and a shaving curls up from the wood.  Further imagine you did this every cm up the wood, you'd have a row of shavings standing out from the board.  That is how these aluminum ones appear to have been made.  Obviously the original block was shaped to optimise the process.

The fins wind up perpendicular to the base block, but at the root of each fin, the material is curved and from markings you can tell it was curled out from the block.  I imagine a block of aluminum moving down a conveyor while a large chopper slices into it as it moves, liek a sushi knife slicing a fish.  The block itself appears extruded.



Also, I would think the important question is not whether one way might cool "better" than another, but rather does the method used do a sufficient job.

For example the photo above with the horizontal fins might cool more eficienctly if the fins were vertical, but the question is: does it cool the circuits sufficiiently as is?  To make it vertical might have meant two pieces and thus twice labor to assemble.  Always a consideration in a commercial product.  For a given amount of cooling, maybe a fan is more expensive than a larger but less efficient heatsink on its own.

[dsmnoisemaker]

one of the things i hate about heatsinks is their price..
it´s prudent to make your own heat sink?
i always think to make my own using a long strip of tin and bending it like an accordeon..
would that work ok?

[J M Fahey]

It depends. I *do* make some, because I have a "guillotine" (sheet metal cutting press or shear, don´t know the exact English name) and a folding press, besides sheet metal punchers, riveters, and the like, but it quickly becomes more work than what I´m $aving. Of course, never tin , only aluminum. In fact, I've bought my machines used at broke tin-sheet workshop Bank auctions. On aluminum up to 2 mm they work lake a charm.
For thicker parts I rivet two 2mm ones, with a generous amount of heat-sink grease between them.
Cheap and reliable PC fans have made my work much easier.

[ponchojuan]

The first one could be interesting if you chimney-effect the enclosure and heatsink.  The current holes are way to skimpy.

[joecool85]

The first one could be interesting if you chimney-effect the enclosure and heatsink.  The current holes are way to skimpy.

Which sinks are you referring to when you say the "first one"?

[E]

On the subject of heatsinks, coming from a computer hardware enthusiast could you use heatsinks designed for use on CPUs? For example, the Coolermaster TX3 is only £12 new and although it uses a fan (17dB if you mod it to run on 5/7v as opposed to 12, not sure on how you would power it though... should still be able to deal with these little chips while running passive though) can deal with 130W of heat. If you had the enclosure space for it then you could even modify the circuit to allow for mounting holes.

**edit from admin**
Moved

Cheers

Thing is, it would probably be easier the way these are designed if the chip fit in a socket instead of standing up...

[rowdy_riemer]

Has anyone tried sand casting aluminum heatsinks? DIY aluminum sandcasting is supposed to be pretty easy.