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-   -   Can L25D amps share a common large heat-sink? (http://www.diyaudio.com/forums/class-d/208851-can-l25d-amps-share-common-large-heat-sink.html)

jaistanley 15th March 2012 03:03 PM

Can L25D amps share a common large heat-sink?
 
Hi guys.

I have ordered 8 of the L25D boards to make a high power 8 channel amp to run my active speakers.

I understand that the L25D may produce wuite a lot of heat (90% efficiency at 350W is still 35W per amp) when run at high voltages/power.

Could I replace the heatsink provided on the boards and use heat-slugs to transfer heat to a common large ehat-sink? From what I can gather the fets are electrically isolated from the heat sink so this shouldn't be a problem but I don't nkow about the grounding and if eddy currents make induce noise in the amps.

I would quite like the Hifi2000 case with the heat-sinks built in, then use copper slugs instead of the supplied heat-sink to transfer the heat out.

Can anyone help?

Kind regards,

Jai

jaistanley 17th March 2012 09:50 PM

Well I've been scoping out work and I can get myself some fairly tasty looking slugs made from solid copper.. I just need to know if there's any reason not to do it???

Kind regards,

Jai

gmarsh 18th March 2012 02:39 AM

There might be a tiny bit of capacitance between the FET drains that wasn't there before, but you can calculate that pretty easily. I'm pretty sure it's negligible.

jaistanley 19th March 2012 12:09 AM

Thank you for your response. I'm not sure what the means though, at least I don't know what the consequence of the extra fet drain capacitance would be?

Kind regards.

Jai Stanley

jaistanley 21st January 2013 09:07 PM

Can anyone else offer any advice on this?

After a bit of time off from my project, I am now thinking about what case to buy. I'd like to buy one very large modushop case with heat sinks down each side, and use slugs of copper to take the heat from each amp module to the case heat sinks.

Is this feasible or will it cause me problems? There is a lot of space in the case when I put four on each side, mounted vertically inside.

Many thanks in advance..

Jai

theAnonymous1 21st January 2013 09:35 PM

I think I remember reading in an IRF document that self oscillating amps should not share a common heatsink. Sorry I can't elaborate on that or remember where I read it.

It might be one of those things you won't know unless you try, which I'm sure isn't the answer you want to hear.

doctordata 21st January 2013 10:10 PM

Quote:

Originally Posted by jaistanley (Post 2950126)
Well I've been scoping out work and I can get myself some fairly tasty looking slugs made from solid copper.. I just need to know if there's any reason not to do it???

Kind regards,

Jai

In the reference design 2 channels are mounted on a common heatsink , so why not 8? give it a try on your workbench with an aluminium or copper bar grounded to the PSU GND and see what happens .

Cheers ,
Rens

theAnonymous1 21st January 2013 10:38 PM

1 Attachment(s)
Quote:

Originally Posted by theAnonymous1 (Post 3336381)
I think I remember reading in an IRF document that self oscillating amps should not share a common heatsink. Sorry I can't elaborate on that or remember where I read it.

It might be one of those things you won't know unless you try, which I'm sure isn't the answer you want to hear.

Wow, can't believe I completely forgot I have an amp I built with two IRAUDAMP1 ref boards connected to a single heatsink. That's 4 channels self oscillating with no problems.

redjr 23rd January 2013 01:51 AM

Hey theAnonymous1,

How much does that sucker weigh? With those 4, fairly large trafos, it must tip the scale! :)

theAnonymous1 23rd January 2013 03:47 PM

45 pounds!

I built the thing over 3 years ago and have never even used it. :/


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