Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: joecool85 on April 05, 2006, 07:37:26 PM

Title: Heatsinks for your poweramp
Post by: joecool85 on April 05, 2006, 07:37:26 PM
First - Have a good power supply circuit and a big enough/proper voltage transformer
Second - Big heatsink, there is no such thing as too large of a heatsink

Proper heatsink size for two LM1875 chips, or one LM3886:
(http://www.thatraymond.com/imagehost/lm1875inside.jpg)

Overkill(which isn't a bad thing though):
(http://www.thatraymond.com/imagehost/overkill_heatsink.jpg)
Title: Re: Heatsinks for your poweramp
Post by: skey on June 14, 2006, 11:36:54 PM
Neither of the above heatsinks above seem to take advantage of thermal airflow. 
Sometimes smaller is better if it's less bulky.  Is there any convenient way to figure out a useful minimal size you'd need?
Title: Re: Heatsinks for your poweramp
Post by: RDV on June 15, 2006, 07:14:06 AM
Neither of the above heatsinks above seem to take advantage of thermal airflow.
Sometimes smaller is better if it's less bulky. Is there any convenient way to figure out a useful minimal size you'd need?
The one in the 1st picture does not take advantage of thermal airflow(though it's big enough to not need it), but the 2nd one is outside the cabinet. How much airflow do you need? It's in free air.

Please don't say that a smaller heatsink is better because it's not. The smallest heatsink you can get away with is best for space saving purposes, but there is no heatsink that is "too big".

There is no convienient way to calculate heatsink size other than doing the math from the datasheet.

Regards

RDV
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on June 15, 2006, 08:11:52 AM
The first one does, maybe poorly, but it does.  I drilled 16 holes in the bottom, then 9 holes in the top to allow cold air to come in the bottom and hot air to rise out the top.  It works, trust me I've never had it over heat.  That amp is my computer speaker amp and I've had it on 3/4 volume (really really loud btw, I had no neighbors at the time  :tu: ) for 2 hours or so and no problems.
Title: Re: Heatsinks for your poweramp
Post by: teemuk on June 15, 2006, 08:14:04 AM
The one in the 1st picture does not take advantage of thermal airflow(though it's big enough to not need it), but the 2nd one is outside the cabinet. How much airflow do you need? It's in free air.

Free air means no "concentrated" airflow. Imagine this: Do you feel cooler on a sunny day when it breezes or when it doesn't? It's the same thing with heatsinking, thus fans are the ultimate solution. If you channel the airflow through the heatsink fins (hot air automatically tends to rise up when cool air replaces it) it will be a lot more efficient than when the heatsink is just in free air. For same reason vertical fins are better than horizontal. (Unless the air flows horizontally for some reson i.e. fan). In the first pic I see some holes at the bottom of the chassis, which means there will be a cooling airflow through the fins. IMO this is better than picture 2 solution. However, the heatsink in picture 2 is massive and therefore dissipates more heat. Same size sink in picture 1 configuration would dissipate heat even more efficiently. If you want a very efficient cooling, channel the airflow up through the fins and use a fan to push a huge amount of air for the heatsink. The cool air would replace the warm by itself but the fan just speeds up this process. If the cool air has paths to "leak" away from the fins you loose efficiency. Thus free air heatsink is always less efficient. However, temperature in the chassis may rise higher than temperature outside it. Best solution would be to isolate fins to a separate and well ventilated (airflow from down to up only) compartment in the chassis.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on June 15, 2006, 08:20:54 AM
We know what you are talking about, but there are several problems with fans in guitar amps. 

1.)  You need to get power to it (not a huge deal)
2.)  They make noise, and who wants fan noise in their amp
3.)  If not done properly you will lose your chip from overheating
4.)  Even if done properly, if the fan fails you will overheat your chip
5.)  Big heatsinks look cooler (this is the most important one)

And yes I know about using fans on CPUs and controlling air flow.  I have a dual 2ghz G5 powermac that (if it would let you) run with the case open it would overheat and toast it's CPUs due to improper (or non existant in certain areas of the case) air flow.

* Ok, so I was kidding about #5, but it is true.  Who wants a girly CPU fan in there when they can have a monster like I have on the back?
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on June 15, 2006, 08:22:00 AM
Oh, and both of those amps up top are mine.  The reason for the inefficient huge monster is because it was all I could find on eBay for a sufficient heatsink at the time.  I haven't changed it because I like the comments I get when people see it  :P
Title: Re: Heatsinks for your poweramp
Post by: teemuk on June 15, 2006, 08:58:40 AM
I agree that fans have their problems. I wouldn't stick a fan anywhere near the preamp sections and a separate supply should be used to isolate fan noises. My intention was not to imply that one should save in heatsink size by using a fan. Of course it can be done but I'd rather use both huge heatsink and a fan. IMO, this combination looks even cooler than a massive heatsink alone. But regarding of saving costs, I'm quite certain that a well-built forced cooling solution would cost as much as someone would save in selecting a smaller heatsink - so why bother. However, a configuration that switches the fan on (with hysteresis) when the heatsink temperature rises to a certain level plus a thermal relay to switch off the power when the heatsink temp is too high is the most failsafe solution, don't you agree.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on June 15, 2006, 09:04:10 AM
I think the most failsafe fan solution would be to have a heatsink that is just barely large enough to use passively, then put a fan on it.  This way, if the fan dies, you can still limp along till you fix the fan.  And yeah, a big sink with a fan on it would look cool.  I didn't bother on mine since it is so huge, plus I wanted a simple solution.  And there is nothing more simple for a heatsink than just grabbing the biggest one you can afford and bolting a chip to it lol.
Title: Re: Heatsinks for your poweramp
Post by: RDV on June 15, 2006, 09:44:56 AM
With proper design, filtering, and load, these amps run fairly cool though really. A huge heatsink is really not neccessary but doesn't really hurt either. If you run two chips bridged or parallel, there almost isn't a big enough heatsink period, and fan cooling is almost a neccessity. This is more true as a guitar amp than in music reproduction however due to the dynamic range of the guitar.

RDV
Title: Re: Heatsinks for your poweramp
Post by: teemuk on June 15, 2006, 11:39:37 AM
I wouldn't trust only on heatsinking a high power amplifier in gig situations. The ambient temperature on stage is huge. It's safe to assume the power dissipation might start from heatsink temp of 40 degrees of celcius not nominal 25.
Title: Re: Heatsinks for your poweramp
Post by: RDV on June 15, 2006, 12:14:49 PM
I didn't bother on mine since it is so huge, plus I wanted a simple solution. And there is nothing more simple for a heatsink than just grabbing the biggest one you can afford and bolting a chip to it lol.
The only way you'll overheat that one is to actually outdo the heat transfer rate. It's possible with a 4 ohm load but unlikely with an 8 ohm load. The Spike protection would finally kick it at that kind of level.

RDV
Title: Re: Heatsinks for your poweramp
Post by: RDV on June 15, 2006, 12:17:12 PM
I wouldn't trust only on heatsinking a high power amplifier in gig situations. The ambient temperature on stage is huge. It's safe to assume the power dissipation might start from heatsink temp of 40 degrees of celcius not nominal 25.
If I ever use a DIY chipamp for gig purposes it will be fan-cooled. I doubt it ever happens though. There's too many inexpensive commercial amps out there. I just use them as stereo equipment and practice amps.

RDV
Title: Re: Heatsinks for your poweramp
Post by: Stompin_Tom on August 23, 2006, 03:22:06 PM
uh... I was looking at this guy's site (he sells kits and completed amps) and his heatsink is pretty small (about half way down the page):

http://www.audiosector.com/chassis_integrated.shtml

Is there something special about copper that you could use a chunk like that instead of the standard heatsinks like Joe used? AND what *possible* effect could the heatsink have on the audio performance of the amp!?!?!?
Title: Re: Heatsinks for your poweramp
Post by: teemuk on August 23, 2006, 04:59:59 PM
Copper has a better heat transfer than aluminium. A cool amplifier would perform better than a hot one (at least the semiconductors would live longer if nothing else).

But anyway, in my opinion that heatsink doesn't look very efficient: It is indeed pretty small and even more, it has no fins! I bet that piece of copper has also been a lot more expensive than a "less sexy", but adequate aluminium heatsink. The most stupid part is, who's going to see it when it's inside the chassis anyway! And speaking of the chassis, where are all the ventilation holes! Got to admit that the chassis looks pretty sturdy though, I bet it acts as a heatsink itself. Doesn't look that impressive IMO. Also, I wonder what "the possible sonic improvements" and "better damping" are... So far no-one has been able to prove that heatsink material, aside effects of heat transfer of course, would do anything to operation of the amplifier.
Title: Re: Heatsinks for your poweramp
Post by: ApexJr. on January 16, 2007, 03:05:16 PM
If your intereted in HEATSINKS I have some in stock..

www.apexjr.com/Sinks.htm

Steve @ Apex Jr.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on January 14, 2008, 08:58:09 AM
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.
Title: Re: Heatsinks for your poweramp
Post by: mad hatter on April 29, 2008, 03:11:46 AM
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.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on April 29, 2008, 07:27:33 AM
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?
Title: Re: Heatsinks for your poweramp
Post by: mad hatter on May 02, 2008, 10:25:26 PM
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.
Title: Re: Heatsinks for your poweramp
Post by: mad hatter on May 02, 2008, 10:31:43 PM
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?
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on May 03, 2008, 07:28:32 AM
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.
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on May 31, 2008, 10:55:12 PM
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.                   
Title: Re: Heatsinks for your poweramp
Post by: Enzo on October 16, 2008, 12:30:20 AM
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.
Title: Re: Heatsinks for your poweramp
Post by: dsmnoisemaker on January 01, 2009, 12:30:19 PM
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?
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on June 13, 2009, 03:15:25 PM
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.
Title: Re: Heatsinks for your poweramp
Post by: ponchojuan on September 16, 2009, 12:35:36 PM
The first one could be interesting if you chimney-effect the enclosure and heatsink.  The current holes are way to skimpy.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on September 17, 2009, 06:28:42 AM
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"?
Title: Re: Power amps - and power supplies
Post by: E on January 26, 2010, 03:18:05 PM
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...
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 09, 2010, 02:53:27 PM
Has anyone tried sand casting aluminum heatsinks? DIY aluminum sandcasting is supposed to be pretty easy.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on December 09, 2010, 02:58:32 PM
Has anyone tried sand casting aluminum heatsinks? DIY aluminum sandcasting is supposed to be pretty easy.

Nope.  Do you mean actually smelting aluminum and pouring it into a cast?  Also, not sure you'd be able to get a flat enough surface when done.  The side the chip mounts on needs to be like glass ideally.
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 09, 2010, 05:03:25 PM
You could flatten the mounting surface afterwards. Or better yet, build a mold template and use lost wax casting.
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 10, 2010, 12:11:26 AM
Well, in fact I *did* something like that, back in the Stone Age.
There were extruded heatsinks available, but fins run along the extrusion axis, and I needed transversal ones, to make my own vwersion of "big" US/Japan rack power amps, where they were used as the sides of the rack cabinets.
*Huge* heatsinks !!!
I made a wooden model, sandcast them, cleaned the very rough surface by airsanding (casting sand adheres to the surface) and last but not least, had to find a guy with a machine that mills aluminum engine blocks, I needed *one* surface quite flat to mount transistors.
Truth is: a lot of work, and the engine block guy charged more for his work than al, the other costs put together. Not worth it.
What I still do, is cut, bend and rivet 1/16" aluminum sheet, to build quite fancy heatsinks.
That *is* cost effective.
PC 12V fans have made the problem much smaller; any heatsink is 300/400% more efficient if blown cold air, and PC fans are very cheap and reliable.
Sometimes I buy surplus CPU fans and heatsinks and bolt them to existing amps (think Bandits, Fender M80, etc.) which use the chassis as heatsink.
Title: Re: Heatsinks for your poweramp
Post by: phatt on December 10, 2010, 03:36:40 AM
Sand Casting,, jeezz mate long gone :lmao:

If you ever see how fast Ally comes out of an extrusion machine you will instanly see the folly of the idea.

Casting Only used now for specialised applications.

Trust JMF to try it,,,  ::) Somehow that does not suprise me as he has been known to try the impossible.  :lmao:

Re Fans,
= Cheap crap in my opinion,,, If one cares to look at almost any industry a proper heat sink is not cheap and in this day Fans are proly 10 times cheaper that a heat sink.

A fan might look trick but WILL ONE DAY STOP!!!  Whereas a correctly designed heat sink will NEVER FAIL.
Phil.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on December 10, 2010, 08:16:19 AM
Sand Casting,, jeezz mate long gone :lmao:

If you ever see how fast Ally comes out of an extrusion machine you will instanly see the folly of the idea.

Casting Only used now for specialised applications.

Trust JMF to try it,,,  ::) Somehow that does not suprise me as he has been known to try the impossible.  :lmao:

Re Fans,
= Cheap crap in my opinion,,, If one cares to look at almost any industry a proper heat sink is not cheap and in this day Fans are proly 10 times cheaper that a heat sink.

A fan might look trick but WILL ONE DAY STOP!!!  Whereas a correctly designed heat sink will NEVER FAIL.
Phil.

I agree I'd rather have a nice (read: large) heatsink than a fan, but if cost/time/space is the issue, fans can work.
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 10, 2010, 09:15:34 AM
Well, in fact I *did* something like that, back in the Stone Age.
There were extruded heatsinks available, but fins run along the extrusion axis, and I needed transversal ones, to make my own vwersion of "big" US/Japan rack power amps, where they were used as the sides of the rack cabinets.
*Huge* heatsinks !!!
I made a wooden model, sandcast them, cleaned the very rough surface by airsanding (casting sand adheres to the surface) and last but not least, had to find a guy with a machine that mills aluminum engine blocks, I needed *one* surface quite flat to mount transistors.
Truth is: a lot of work, and the engine block guy charged more for his work than al, the other costs put together. Not worth it.
What I still do, is cut, bend and rivet 1/16" aluminum sheet, to build quite fancy heatsinks.
That *is* cost effective.
PC 12V fans have made the problem much smaller; any heatsink is 300/400% more efficient if blown cold air, and PC fans are very cheap and reliable.
Sometimes I buy surplus CPU fans and heatsinks and bolt them to existing amps (think Bandits, Fender M80, etc.) which use the chassis as heatsink.

You rock, JM, you've done everything!!!
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 10, 2010, 09:20:58 AM
Sand Casting,, jeezz mate long gone :lmao:

If you ever see how fast Ally comes out of an extrusion machine you will instanly see the folly of the idea.

Casting Only used now for specialised applications.

Trust JMF to try it,,,  ::) Somehow that does not suprise me as he has been known to try the impossible.  :lmao:

Re Fans,
= Cheap crap in my opinion,,, If one cares to look at almost any industry a proper heat sink is not cheap and in this day Fans are proly 10 times cheaper that a heat sink.

A fan might look trick but WILL ONE DAY STOP!!!  Whereas a correctly designed heat sink will NEVER FAIL.
Phil.

If only we all had extrusion machines.

As silly as it might be, I might give sand casting a go. I've been looking for an excuse to sand cast something anyway.

Well, I might only dream about it. School is eating up all my free time. Next week, I have to take a calc II final exam that is big enough that I have to show up on two different days to take it. Then, it'll be time for two more classes, including Calc III.

If I ever do give it a go, I'll set up a power transistor whose only job is to get hot, and I'll try to measure it's effectiveness. If I can't get a flat enough surface for mounting, it'll no doubt get warmer than it should.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on December 10, 2010, 09:58:10 AM


If only we all had extrusion machines.

As silly as it might be, I might give sand casting a go. I've been looking for an excuse to sand cast something anyway.

Well, I might only dream about it. School is eating up all my free time. Next week, I have to take a calc II final exam that is big enough that I have to show up on two different days to take it. Then, it'll be time for two more classes, including Calc III.

If I ever do give it a go, I'll set up a power transistor whose only job is to get hot, and I'll try to measure it's effectiveness. If I can't get a flat enough surface for mounting, it'll no doubt get warmer than it should.

Keep us posted if you do, could be interesting at least.
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 10, 2010, 10:40:30 AM
A *large* thick toothed file will work wonders, and be it's own reference as to what "flat" means.
That said, "home" sandcasting doesn't strike me as particularly easy.
I had them made at a casting shop, which already had the melting pots, ovens, "sand boxes", sandblasting equipment, grinders, etc.
As to why I made a lot of things, Argentina was a Tariff protected market until 1976, where we "opened" our Economy, under bayonet pressure, paying 30000 "dissapeared" to make it possible.
We also went from 4% to 35% (real) unemployment and increased our External Debt to 50x the original one.
In 1965 *we* sold electronics to Korea, made everything (including Mallory capacitors, CTS pots, Jensen speakers, FAPESA tubes, Texas semiconductors) except color picture tubes.
*Anything* which had a market could be made locally at a profit.
There was a short "Spring" in the 80's where we even made submarines, Saddam's missiles, AMX tanks, sold nuclear reactors to Canada and Australia, etc.
Then our Industry got clubbed to death in the 90's, until now.
Oh well.
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 10, 2010, 10:54:52 AM
There's actually A LOT of guys who do their own sand casting. There's a lot of stuff on instructables.com about it.  Check out this example: http://www.instructables.com/id/Ultimate-Guide-to-Making-a-Cheap-but-Effective-Alu/ (http://www.instructables.com/id/Ultimate-Guide-to-Making-a-Cheap-but-Effective-Alu/) I've got a large and small coffee can and some quickcrete saved up. I still need to get the stuff for the mold.
Title: Re: Heatsinks for your poweramp
Post by: phatt on December 11, 2010, 05:56:04 AM
Hi Rowdy R,
Just remember your sand has to be DRY and I mean Really DRY.
Any mosture and boom it will explode in the cast and destroy itself.

Remember this is molten metal you are playing with,,,
YES I've Worked in both a Steel foundry and also a small Bronze Art foundry.

Lost Wax (done correctly) will yeild extremly accuate results,,, far better than sand.

If you just can't help yourself ( and it sounds like that might be the case LOL )
Then consider taking on pedal cases!
These can be made from *Monks metal* which melts at fairly low temp.
(about 400 deg C from memory,,, been a long time)
 A soft "Zinc based Alloy" used to make door handles and automotive parts,,,and Yes the Boss pedals also.

You would then have something Totally Original and likely worth selling :tu:
just look at the Mayer Octavia pedal as example,,, very unique and oh so cool. 8|
Cheers Phil.
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 12, 2010, 01:06:47 AM
Nothing like steam explosions. Heheh  xP

I've considered doing pedal cases, too. I've read on one site about using zinc with aluminum as a strong alloy. Actually, I may have read this from one of the Gingery books. Making a wooden model would be fairly easy. Whatever I do, I'll try to remember to post the results however good or bad they may be. (hopefully no hospital trips from shrapnel)
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 12, 2010, 07:04:13 AM
Making pedal cases would be *great:
Just 2 points to consider:
1) since the metal will fill the mold only by gravity (not aided by high air pressure or centrifugal force) and
2) sand mold walls are cold, prematurely cooling and "freezing" the metal,
you will have to make box walls somewhat thicker (say 3 or 4 mm vs, 1.5 mm as in Hammond boxes) and preferably use a zinc alloy instead of pure aluminum.
You can buy zinc parts to melt for cents a pound at car graveyards (old carburetors, windshield motor cases, handles, water and gasoline pump bodies, etc.)
Just go there and fill your trunk for peanuts.
Check: http://en.wikipedia.org/wiki/Zamak
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 12, 2010, 09:05:29 PM
I can also use American pennies. It would not be as cheap, but they are easy to find. I'm, of course, not going to do that, though, because that would be illegal.  0:)
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 13, 2010, 12:09:59 PM
Don't think so.
If anything, making pennies out of Zamak, or even better  silver Dollars (Zamak takes *any* metal plating beautifully, including silver and gold) would.
Of course, it might be more profitable too.  ;)
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 13, 2010, 01:20:07 PM
Not talking about making pennies, but using pennies as a source for zinc to make zamak. :)
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 13, 2010, 01:58:26 PM
Sorry, JM, I might have misread your post.
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 14, 2010, 12:09:39 PM
You *read* it right, but I think you missed the
 ;)
 ;)
 ;)
 ;)
 ;)
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 14, 2010, 12:28:16 PM
Hehe.

It seems like I figured out one time that using pennies as a source for zinc would cost about twice the market value for zinc. I imagine the negligible amount of copper plating wouldn't hurt anything. I think some Zamak alloys even contain a bit of copper. But it certainly would be cheaper to find scrap zinc.
Title: Re: Heatsinks for your poweramp
Post by: spud on December 15, 2010, 12:45:13 PM
Hey I'm new here and I'm wanting to build a chip amp but when I started doing some reading and I realized that a heat-sink would be essential if I wanted any real power.  I did some searches and I found these guys:

http://www.heatsinkusa.com/storename/heatsinkusa/ViewDept-269591.aspx (http://www.heatsinkusa.com/storename/heatsinkusa/ViewDept-269591.aspx)

Has anyone used this vendor?  Also, what size would be appropriate for a LM1875 chip amp implementation running about 15 - 20w? Probably 24v or so.  I figure the small 1 inch one would suffice since it's rated at 2.15o C/W/3 or am I not understanding the rating they give? 

Some background: I've built a few pedals (BSIABII, Double D) and have prototyped a few others (Plexi-izer, UBEscreamer, Hot-harmonics), finished 2 tube amps (AX84 HO and a Firefly) and still have 1 on the bench (a 5E3).  I've been considering taking a pedal like the ROG DD  and mating it to a chip-amp for some time but never taken the plunge.  I've got a bunch of parts (Caps, Res, Trans, Op-amps, etc) I've collected (I try to buy in bulk) and I started looking around for amp chips and I realized I needed a heat sink - but most are pretty pricey for what you get (did I mention I'm a cheap) which is a hunk of metal - but I found these guys and was wondering if this was a good source and what size(s) to get.   Optionally, if anyone can help me with doing the calculations to figure it out myself, that would be great.   

BTW - this seems like a real cool site and I'm jazzed that I found it.  Been reading a lot of the threads - great ideas and projects.

Thanks -

Jim
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 15, 2010, 01:24:44 PM
I know this isn't related to the OP, but what did you think of the firefly? I'm kinda considering building one.
Title: Re: Heatsinks for your poweramp
Post by: spud on December 15, 2010, 02:31:22 PM
Hey - well I like it, here's my implementation of it - called the Small Fry to avoid confusion with the original:

http://s252.photobucket.com/albums/hh7/spudjds/Public/Builds/AMPS/SF/ (http://s252.photobucket.com/albums/hh7/spudjds/Public/Builds/AMPS/SF/)

I added a tone control (By-passable) with a scooped switch.  Also added a switch to allow use of a ECC99 in addition to the 12au7 - rest of it is stock.  I recently re-did the grounds and I have a problem to debug with the boost - no work.  Oh, well - I can't leave well enough alone  ::)

My mods are all documented in the layout and the schematic there. 

Jim
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 15, 2010, 03:08:54 PM
Cool deal. Thx for sharing that.
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 15, 2010, 05:51:56 PM
Hi.
You somewhat misread the data but no big deal.
That last "3" means that this heatsink provides those 2.5ºC/W for a 3 inch length; they do not state it for a 1" length nor provide the dissipation vs.length table, which amazes me.
Anyway, on experience I cantell you that the actual value will be around 4ºC/W and even more important: it will be enough for a 25W chipamp.
In fact I use a slightly better 20 fin , 2 inch length one for my 100W amps with excellent results.
You will also be able to use a piece of 1/16" flat aluminum sheet, 4" by 6" size, which you may scrounge for even less money.
Title: Re: Heatsinks for your poweramp
Post by: spud on December 15, 2010, 06:50:47 PM
Hey JM thanks - so I can go to Home Depot and get a 1/16" sheet and cut it to 4 x 6" and use that for the LM1875?  Wow - cool idea.  I like that. With about a thicker piece like 1/8" - would that mean a smaller size?  By what proportion?

WRT to the heatsinkusa product: so I can use a 1" sized one for the LM1875 or does it need to be 3"?   I may go with the 5.x size if it means I can get smaller piece - it's rated at 1.15 vs 2.3 for the 4.x" one I linked. 

So is there a formula to calculate this or some rule of thumb to go by?

Thanks for the info -

Jim
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on December 15, 2010, 11:38:52 PM
Basically yes.
Aluminum is a great heat sink material.
I make my own chassis and have always used aluminum, so by just bolting transistors or chips to the chassis (using proper micas, grease, etc. of course), I have "free" heatsinks. WOW !!.
Your 1/16" is fine and still can be bent without heavy machinery.
You may mount a flat sheet with spacers or bolts and nuts "in the air", remember you want free flow of air around it, but being able to bend it in an "L" shape makes mounting easier.
1/8" will work better because heat across it will be more uniform, good, but you still need a certain surface because the last link of the chain is heat transfer to air.
Commercial heatsinks have the added advantage of providing a lot of surface in a smaller size.
There are formulas, which I have not found very accurate for everyday work, or empirical dissipation tables provided by heatsink manufacturers.
Title: Re: Heatsinks for your poweramp
Post by: rowdy_riemer on December 16, 2010, 12:56:00 AM
The first thing I noticed when I first opened my Crate GFX-212 was that the transistors were mounted to the chassis.
Title: Re: Heatsinks for your poweramp
Post by: scooperman on March 28, 2011, 09:11:11 AM
for bench testing circuits, an old lawnmower or motorcycle finned cylinder head works fine as a heatsink.  Bob Pease used a VW cylinder head when testing new chips.
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on March 28, 2011, 10:12:58 AM
for bench testing circuits, an old lawnmower or motorcycle finned cylinder head works fine as a heatsink.  Bob Pease used a VW cylinder head when testing new chips.

Great idea.  You could use it as a final product I'm sure as well, albeit much heavier than a more traditional solution.
Title: Re: Heatsinks for your poweramp
Post by: spud on April 07, 2011, 12:06:38 PM
How about an old CPU heatsink from a dead computer?  Would that be usable given that you have some thermal goop to put on there.

Jim
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on April 07, 2011, 12:47:20 PM
How about an old CPU heatsink from a dead computer?  Would that be usable given that you have some thermal goop to put on there.

Jim

A computer CPU heatsink is good for a small 5-10w amp without a fan.  With a fan it should be good for 50-100w depending on the heatsink.  That said, I never recommend using a fan on a heatsink.  It's one more part that could fail.  Lots of companies do it though, mostly with good success.
Title: Re: Heatsinks for your poweramp
Post by: JPHeisz on April 07, 2011, 12:55:45 PM
I've used heatsink USA (barrredboss on Ebay) a couple times and his stuff is excellent and good value.
A great (cheap) source for heatsinks are old amps/receivers at Goodwill, thrift shops etc. They don't need to be working. These are also good for a wealth of screws, standoffs and other hard to get items - transformers too. Worthwhile grabbing a couple or more to scrap for parts.

The side heatsinks of this monster are from HeatsinkUSA:
Title: Re: Heatsinks for your poweramp
Post by: spud on May 04, 2011, 04:25:10 PM
Hey all,

This link was posted over at AX84 -

http://homepages.which.net/~paul.hills/Heatsinks/HeatsinksBody.html (http://homepages.which.net/~paul.hills/Heatsinks/HeatsinksBody.html)

Interesting article. 

Jim
Title: Re: Heatsinks for your poweramp
Post by: RubberSalt on November 01, 2011, 04:25:56 PM
Why not just use bad ass cpu heatsinks? :-p or water cooling:-p


Most computer fans will operate on 5 volts - you wont hear that at all, fan wise.  I'd run 2 of them for a push pull set up, if 1 failed... still got 1 to go on.  Set up some LED indicators for each fan, if fan fails to start led lights up or something.

You could also go as far as using thermo resistors, higher temp would allow for more current/voltage flow.  Means fan will go faster. If its hot enough to make it go fast - you wont hear it mechanicaly.  Computer fans are also brushless, so not difficult to silence the eletricty.

If i build any high powered amps soon, I'll be using heat pipes.
Title: Re: Heatsinks for your poweramp
Post by: Evil_Food on November 02, 2011, 01:33:58 PM
My main worry with brushless DC motors would be EMI... haven't tried anything myself though.

Has anyone had any experience with that?
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on November 04, 2011, 09:29:27 AM
I always use 12V CPU power supply type fans (not the small microprocessor ones but the 3 1/4" ones) on my 300W amps.
Yes, they *do* cause some interference, not RFI type (they are brushless) but magnetic: the rotor itself is a rotating multi-pole magnet, plus the coils are being switched on and off by squarewaves very quickly.
So: no reverb pickup heads close to them, and no sensitive preamp inputs either.
I put them on an end of the cabinet, and "shielded" from the electronics by the power transformer, which itself is a noise source, so both "live" on the opposite end of the inputs.
No problem at all with my Bass amps; but on my Powered Mixers, with inputs all over the place, sometimes I have problems with some buzzy hum injected in the Master section ... the culprit is easily found just by blocking rotation with a finger.

Title: Re: Heatsinks for your poweramp
Post by: polo16mi on November 11, 2011, 08:48:32 PM
Silly question:

Why cant i use some piece of steel framing (steel galvanized) as heatsink? I have a lot of pieces of them, and it comes in several sizes...
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on November 11, 2011, 10:14:57 PM
No, not steel.
Buy *aluminum* rails used to make doors and windows, they may be used, if at least 1.5 or 2mm thick , plus having at least 10x10cm (4"x4"), preferrably 10x20cm (4"x8") or larger.
If *somewhat* narrower (say, 3", they should be proportionately longer.
Somebody who makes such doors and windows may have lots of leftover pieces, in small sizes useless for him, but good for you.
At least part of the surface where you bolt the chip must be flat and make good thermal contact.
Always use thermal grease.
Some examples of extruded aluminum which can often be had for free , or peanuts, if leftover useless for the metal shops:
(http://www.metalesgalvani.com.ar/proceso/perfiles.jpg)
(http://suelos-fachadas.com/PERFIL-DE-ALUMINIO.gif)
(http://www.bricopage.com/como_se_hace/decoracion/imagenes/metal-aluminio.jpg)
Title: Re: Heatsinks for your poweramp
Post by: teemuk on November 12, 2011, 10:01:39 AM
^ Cool idea, cheap, I like the recycling aspect of it, and with some thought process it likely could also make a great aestetic design detail in the vein of another aspect I really like: function defines form. Have to store that to my brain and use it when I run out of cannibalised heatsinks.

Oh, generic trash metal yards will be packing literally tons of this stuff.

But I think I wouldn't use that stuff for any heavy-duty heatsking, though; my impression with those leftover frame pieces is that they are kinda flimsy (effective heat spread throughout the heatsking requires a thicker baseplate) and the convection would be somewhat diffucult to arrange since that stuff doesn't have too many "fins" and overall the shapes are pretty weird. I had some of that stuff around and actually thought about heatsink purpose for e.g. regulator chip but back then (and still) I had a good supply of small heatsinks scavenged from equipment found from trashpiles.
Title: Re: Heatsinks for your poweramp
Post by: Roly on May 02, 2012, 11:27:30 AM
Also, what size would be appropriate for a LM1875 chip amp implementation running about 15 - 20w? Probably 24v or so.  I figure the small 1 inch one would suffice since it's rated at 2.15o C/W/3 or am I not understanding the rating they give? 

Just to take these numbers as an example.

Amps power output = 20 watts
Heatsink rating = 2.15 degrees C per watt

Assuming the amp has a pretty typical efficiency of 50%, then the heatsink has to dispose of 20 watts.

20 * 2.15 = 43 degrees C

This is the temperature rise at full power over the ambient temperature.  Normally we would assume 25 degrees C ambient, but on-stage under lights a much safer assumption is 40 degrees C.  To get the actual operating temperature at full power we add the rise to the ambient;

40 + 43 = 83 degrees C.

We haven't accounted for the thermal resistance of the chip to case, or case to heatsink (via any insulating washer), so we can guess that the actual chip temperature will be closer to 100 degrees C.

As a rule of thumb the absolute maximum chip temperature shouldn't be hotter than 100 degrees C, so this setup would be shaving it a bit too fine for comfort (or overall chip life), so really a heatsink with a much lower thermal resistance is required.

The quoted thermal resistance of 2.15 degrees per watt also assumes optimum mounting of the heatsink, fins vertical, in genuine free air, and not exposed to any external heat source (such as stage lights).

Heatsinks are made the shapes they are for good reasons, thick where the devices(s) mount so they conduct heat well out to the thinner fins.

A couple of "rules" of heatsinking are that you always need more heatsink than you think; and quoted thermal resistances tend to be optimal, or even optimistic.  On the plus side, even a small amount air movement from an under-run fan makes a large difference to heatsink performance; however even a strong blast of air won't turn a seriously undersized heatsink into a wonder heat dissipator.

First design for sufficient passive cooling, then add a thermally controlled fan to cover those nasty extreme situations that crop up.

Here's my indicating proportional "thermofan" design that has been used in several amps including a re-creation of an Acoustic 360 by J.C.Maillet;

http://www.ozvalveamps.org/techsite/thermofan/thermofan.htm (http://www.ozvalveamps.org/techsite/thermofan/thermofan.htm)
Title: Re: Heatsinks for your poweramp
Post by: joecool85 on May 03, 2012, 11:52:55 AM
Here's my indicating proportional "thermofan" design that has been used in several amps including a re-creation of an Acoustic 360 by J.C.Maillet;

http://www.ozvalveamps.org/techsite/thermofan/thermofan.htm (http://www.ozvalveamps.org/techsite/thermofan/thermofan.htm)

VERY cool!  If you don't mind, I'd love to have you start a thread here about this and include schematics, diagrams, pictures, whatever you can. 
Title: Re: Heatsinks for your poweramp
Post by: bry melvin on May 05, 2012, 01:28:39 PM
On using computer heat sinks: I've been adding these (P4 or socket7 heatsinks  to Fender15G/R amps that I fix (TDA2050) on a regular basis.  I've been using a pair of these on 4ohm cabs in my studio. I've been buying returned  Fender squier/amp/guitar combos( repair and resell) for a while most of these have a burned out TDA 2050. For larger amps I've found the massive P3 passive (no fan) heatsinks Compaq used to use in P3 Servers and business desktops work quite well.

Also STAY AWAY from some of those Silver Computer heat sink goops some of them are CONDUCTIVE electrically.
Title: Re: Heatsinks for your poweramp
Post by: nachus001 on September 05, 2016, 10:41:48 PM
Hey

What do you think of a design like this one? An aluminium chassis (2mm thick Al sheet) with sides bent to 6 cm
The power board with it's transistors attached to the chassis, and the back side of the chassis with riveted fins
made of an U shapes structural Al bar.

This design may be useful? Or are the fins useless because of the poor thermal contact with the rest of the chassis?
I've seen this kind of heatsinks used in 7.1 surround sound equipment, (aluminium plate with riveted fins, but the PA
for this equipment is a class H chipamp that should run very cool all the time, or most of the time.
Title: Re: Heatsinks for your poweramp
Post by: J M Fahey on September 07, 2016, 03:58:22 AM
IF the chassis is 2mm thick, power transistors are near the back panel and U shaped channel aluminum is not only riveted, but you add thermal grease between them and the back panel .... yes, they will work very well.
Title: Re: Heatsinks for your poweramp
Post by: flester on December 10, 2017, 05:49:31 AM
Does an opamp  like the lm386 need a heatsink? While testing a breadboard build i pressed down on the chip and suddenly went ouch! as it had got pretty hot. (It may have been connected wrong ny the wau)t least I willl remember the name of the chip as its branded on my finger.







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Title: Re: Heatsinks for your poweramp
Post by: tonyharker on December 10, 2017, 12:57:54 PM
The LM386 is not an op amp but a power amp, albeit low power.  It could be getting hot because it it is oscillating. It should be cool if it is idling ie not passing a signal.
Title: Re: Heatsinks for your poweramp
Post by: Jazz P Bass on December 10, 2017, 01:55:41 PM
The LM386 is Not simply an opamp.
It is a power amplifier in it's own right.

The quiescent current with a 12Vdc supply is in the milliwatts.
So that wont make you say ouch.
The power dissipation of the package is 500 milliwatts (1/2 watt).
Again, no need for a heatsink.

If the device got that hot, it is hooked up wrong.
Most probably it is now bad.
Title: Re: Heatsinks for your poweramp
Post by: flester on December 11, 2017, 09:22:07 AM
The LM386 is Not simply an opamp.
It is a power amplifier in it's own right.

The quiescent current with a 12Vdc supply is in the milliwatts.
So that wont make you say ouch.
The power dissipation of the package is 500 milliwatts (1/2 watt).
Again, no need for a heatsink.

If the device got that hot, it is hooked up wrong.
Most probably it is now bad.
Thanks. Almost certainly was mis-wired but have sorted it out and runs fine on the breadboard and no longer gets hot. Seems to still work but I have spares anyway

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Title: Re: Heatsinks for your poweramp
Post by: Jazz P Bass on December 11, 2017, 10:45:07 AM
Those are nice Ic's.

Good to know that they are robust enough to survive being 'hooked up wrong'.

Any idea what mistake you made?

Title: Re: Heatsinks for your poweramp
Post by: GB on August 09, 2018, 06:38:37 AM
Hi Guys... notwithstanding the (very valid) point about them failing... Cooling Fans can be very effective... potentially reducing the size of a given heatsink by 50% - or more.
Attached is a pic of a 100 watt with a relatively small heatsink - but with two 40mm fans directed down the cooling fins. The amp runs of a nominal 50 volt supply so these are two 24 volt DC units - with a little bit of additional circuitry to ensure that the voltage is equally distributed between them.
Bottom line it works very well.
PS. I have contemplated adding some sort of thermal protection (fuse or breaker) as a last line of protection - but haven't got that far yet.

GB