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-   -   to much heat! (http://www.diyaudio.com/forums/chip-amps/126306-much-heat.html)

kanifee 13th July 2008 12:43 PM

to much heat!
 
I'm getting a little concerned as my new LM3886 chipamp.com amp gets a tad warm on the heat sinks after 2 4 minute songs on full volume, hot to the point you cant touch them for more than a second.
The amp itself seems to be working pretty much spot on apart form the heat problem, i have a 225va 230v 2x25v secondary transformer with a p4 heat sink on each chip. is it just a case of not enough heat sink or is the supply to big or some other problem?

woody 13th July 2008 02:07 PM

Are you using a peniem 4 heat sink ? Are you using it with a fan?
One of those won't do much at all without a fan the fins are too
close for use without a fan.

Nuuk 13th July 2008 05:33 PM

A lot depends on how much work the amp has to do to drive your speakers.

My VBIGC works fine on PC heatsinks (one per chip) but my speakers are over 95 db efficient and an easy load.

kanifee 14th July 2008 01:57 PM

Checking the specs for mine shows they are 89db efficiant.

bego2 14th July 2008 03:58 PM

it`s ok. my heatsink is like yours. hot as hell :D lm3886 has thermal protection, dont wory.

AndrewT 15th July 2008 08:27 AM

if you run the chip hot then Spike protection triggers much earlier than the cold specifications (Tc=25degC).

If you require good performance then run the chips as cold as possible (Tc<=40degC).
If you want better performance use higher impedance speakers.
If you want better still, then use high efficiency, high impedance speakers.

owen 15th July 2008 08:46 AM

A little simplistic.

High impedance isnt the main issue - as impedance is a vector sum, and not a linear sum. So you can have a speaker with high efficiency and high impedance, that has a nasty as hell phase pofile that amps really do not like....

Back to the question in hand.

the 3886 is a dual power opamp. so that little heatsink will be dissipating 50+ W insufficent area will make its temperature rise quickly... Not a great plan, as SPIKE sounds truely nasty.

So a bigger heatsink is in order if you regularly use it at full tilt. It will need to be large, black, and expensive, but the chip will love you for it.

I do however feel the need to ask what kind of ear protection you are using - even with a mid 80s db efficient speaker, you will be cranking more than enough volume to cause long term damage, especially if you repeat it on a regular basis...



Owen

AndrewT 15th July 2008 08:54 AM

Quote:

Originally posted by owen
.....High impedance isnt the main issue - as impedance is a vector sum, and not a linear sum. So you can have a speaker with high efficiency and high impedance, that has a nasty as hell phase pofile that amps really do not like....
and a low impedance high reactance speaker will be even worse trying to reproduce the same SPLs.
Now exacerbate the problem with a low efficiency speaker and the reactance problem is worse still.

Be kind to your chipamp is as simple as it gets - KEEP IT COOL.

kanifee 15th July 2008 09:19 AM

Im using full tilt when working in other rooms/garden but at the moment i feel the need to keep poping back to check she is ok, i havnt invested in a case yet so i suppose ill have to treat my GC to a prezzy and get one of these

http://i12.photobucket.com/albums/a2...ack3u_0000.jpg

i take it that will do the job nicely?
this one is from modushop.biz does any one know any other companys that ship cases like this to the uk?

artquake 15th July 2008 09:34 AM

you find them here and even here (but a little more expensive, because he get's it from the first link)

i've bought the same but with This Frontplate ... :)

regards
artQuake


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