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Old 19th June 2008, 03:37 PM   #1
thoronx is offline thoronx  Yugoslavia
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Default 2 x LM3875T on the same heatsink ?!

Hi,

I'd like to ask for an advice, I have a plan to build an amp using lm3875T (non-insulated case with -Vcc on its tab) and I want to mount both of the chips on the same heatsink, without any mica insulation between the chip and the heatsink, is it possible ? I see no reason why not to do so, 'cose both of the tabs of the chips are on the same potential.

Insulate the chip from the heatsink or not , this is My question.

ThanX.
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Old 19th June 2008, 04:40 PM   #2
thoronx is offline thoronx  Yugoslavia
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something more to add to my thread

... of course the heatsink will be far from touching anything inside the amp's case.
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Old 19th June 2008, 05:17 PM   #3
Nordic is offline Nordic  South Africa
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You will need to Isolate the 2 chips that is all... if the sink is not exposed You can give it a try without... Of course the sink then needs to be insulated from the case...
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Old 20th June 2008, 06:22 AM   #4
ratza is offline ratza  Romania
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On my system I have 2 LM3886T on the same heatsink, without any isolation, which are running at least 6 hours per day without any problems.
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Old 21st June 2008, 09:04 AM   #5
AndrewT is offline AndrewT  Scotland
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Hi,
single PSU or dual?
If single, then the sink will sit at -Ve and must be insulated from the case and also protected from objects falling onto it.

Direct chip to sink with Thermal compound is the way National (and probably others) specify their best performance figures.
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Old 21st June 2008, 12:09 PM   #6
ratza is offline ratza  Romania
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Single PSU. If he makes monoblocks he will need for sure two heatsinks
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Old 21st June 2008, 02:16 PM   #7
thoronx is offline thoronx  Yugoslavia
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monoblocks, packed in the same case
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Old 21st June 2008, 08:32 PM   #8
AndrewT is offline AndrewT  Scotland
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then you must insulate the chipamps from each other.
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Old 23rd June 2008, 06:06 AM   #9
thoronx is offline thoronx  Yugoslavia
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actually it will be a simple stereo version with shared psu (one xmfr, with center tapped secondary, 1 x graetz, caps...)
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Old 23rd June 2008, 09:41 AM   #10
ratza is offline ratza  Romania
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Well then go for both on a single heatsink. My system was made in the same way.
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