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Chip Amps Amplifiers based on integrated circuits

Neurochrome LM3886DR Build
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Old 17th September 2018, 12:25 AM   #421
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by ozenfant View Post
Ah, that I do not have. Any recommendations on how to approach that? I guess literal holes bored through the side would be one approach, or perhaps routing a channel on the inside that exits at the back?
If possible orient the heat sinks such that the fins are vertical. Then either let the heat sinks poke through the side of the chassis or drill a bunch of holes below the heat sink fins and above them for the air to flow through.

Tom
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Old 17th September 2018, 12:32 AM   #422
chrisb is offline chrisb
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Ideally I think you’d want to create a open air path for convection - usually with the fins of heat sinks oriented vertically. With high efficiency class D type amps such as Hypex modules, the thick extruded side panels of something like the DIY Audio store Slimlines work great, but amps like Toms, or the class A ACAs need either surface area exposed to free air, or some other creative heatsink /cooling mechanism with which to dissipate that thermal energy.

OK, I see Tom answered pretty much the same thing
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Old 20th November 2018, 09:56 PM   #423
TioFrancotirador is offline TioFrancotirador  Poland
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Guys,
I have really strange issue. I am running stereo lm3886DR with one smps -/+24V (2x60W/24V). On each lm3886dr board instead of two 1000uf caps I put two 3300uf/50V.
When I connect the amp to the 4R speaker I works perfect. Dc offest less thatn 2mV in both channels. I measured the voltage across the caps and it is either -24V or +24V. Everything is just fine. However after some time (5mins) one of the 3300uf cap in one channel get extremly hot! (the other channel does not have this issue). I checked polarity and it is ok. I replace the cap (thining it is maybe faulty one) but a ran into same issue. Then I just removed this cap and everything works fine ...
Any ideas what might have happend? Please help. It is really strange for me. Why this particular cap get so hot?
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Old 20th November 2018, 10:08 PM   #424
tomchr is offline tomchr  Canada
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One of your SMPSes may be oscillating due to the capacitive load. That would burn significant power in the cap, thereby heating it up.

Tom
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Old 20th November 2018, 10:55 PM   #425
TioFrancotirador is offline TioFrancotirador  Poland
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Originally Posted by tomchr View Post
One of your SMPSes may be oscillating due to the capacitive load. That would burn significant power in the cap, thereby heating it up.

Tom
Thanks Tom,

But is the increased capacitance the cause of oscilation? or one of the smps oscilates because of different reason (like low ESR of caps) and increased capacitance does not have anything to do with this?

Last edited by TioFrancotirador; 20th November 2018 at 11:07 PM.
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Old 21st November 2018, 05:31 AM   #426
tomchr is offline tomchr  Canada
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If you add capacitance, you'll change the feedback loop dynamics. Many SMPSes have a max specified additional cap.

Tom
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