2 x LM3875T on the same heatsink ?!

thoronx · 19th June 2008, 03:37 PM

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.

thoronx · 19th June 2008, 04:40 PM

something more to add to my thread

... of course the heatsink will be far from touching anything inside the amp's case.

Nordic · 19th June 2008, 05:17 PM

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...

ratza · 20th June 2008, 06:22 AM

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.

AndrewT · 21st June 2008, 09:04 AM

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.

ratza · 21st June 2008, 12:09 PM

Single PSU. If he makes monoblocks he will need for sure two heatsinks

thoronx · 21st June 2008, 02:16 PM

monoblocks, packed in the same case

AndrewT · 21st June 2008, 08:32 PM

then you must insulate the chipamps from each other.

thoronx · 23rd June 2008, 06:06 AM

actually it will be a simple stereo version with shared psu (one xmfr, with center tapped secondary, 1 x graetz, caps...)

ratza · 23rd June 2008, 09:41 AM

Well then go for both on a single heatsink. My system was made in the same way.

19th June 2008, 03:37 PM	#1
thoronx diyAudio Member Join Date: May 2007	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.

20th June 2008, 06:22 AM	#4
ratza diyAudio Member Join Date: Dec 2007 Location: Sibiu, Romania	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. __________________ Any solution is a compromise.

21st June 2008, 12:09 PM	#6
ratza diyAudio Member Join Date: Dec 2007 Location: Sibiu, Romania	Single PSU. If he makes monoblocks he will need for sure two heatsinks __________________ Any solution is a compromise.

23rd June 2008, 09:41 AM	#10
ratza diyAudio Member Join Date: Dec 2007 Location: Sibiu, Romania	Well then go for both on a single heatsink. My system was made in the same way. __________________ Any solution is a compromise.

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19th June 2008, 04:40 PM	#2
thoronx diyAudio Member Join Date: May 2007	something more to add to my thread ... of course the heatsink will be far from touching anything inside the amp's case.

19th June 2008, 05:17 PM	#3
Nordic diyAudio Member Join Date: Sep 2005	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...

21st June 2008, 09:04 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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.

21st June 2008, 02:16 PM	#7
thoronx diyAudio Member Join Date: May 2007	monoblocks, packed in the same case

21st June 2008, 08:32 PM	#8
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	then you must insulate the chipamps from each other.

23rd June 2008, 06:06 AM	#9
thoronx diyAudio Member Join Date: May 2007	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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