Multiple TDA's sharing heatsink

aadrian · 18th December 2012, 08:46 AM

Hello all.

This is my first post and I would like to start out with a question regarding sharing the same heatsink (large one) for 3 TDA7294 IC. The heatsink will not be connected to ground or any other wires. The box will be made out of wood so no connection to the box either.

Is this ok or should I avoid sharing the same heatsink even if the size should be ok to handle the heat?

Thanks

KatieandDad · 18th December 2012, 09:48 AM

Do bear in mind two things:-

1. Both ICs MUST be electrically insulated from the heatsink.

2. The heatsink is rated for a single source of heat at its thermal centre. If you mount two ICs away from the centre then the thermal performance of the heatsint will not be as effective - i.e. you will need a bigger heatsink.

As long as you consider both these factors you can mount as many devices to the heatsink as you desire.

csom · 10:12 AM

Although KatieandDad suggested everything , here are my two cents :

I used two TDA2050 ICs together on a heatsink just to test for sometime after first power up.

Since I never play loudly I used a small heat sink ( in the photo below) with mica insulator but they were not sufficient to dissipate the heat.

We need a much bigger heat sink.

aadrian · 18th December 2012, 10:28 AM

thanks for the replies.

Why should the ic's be insulated if the heatsink won't touch any other connection? what could occur?

Mark.Clappers · 18th December 2012, 10:46 AM

The tabs of the IC's are not insulated, so you would effectively be coupling the -Vs via the heatsink. If this is a problem is a different question altogether and can't be answered without more details of the complete setup.

aadrian · 18th December 2012, 10:51 AM

Hi Mark.

yes in essence, the tabs will all be connected to the heatsink. Will this be a problem as long as the heatsink won't be connected with any other electrical element?

JMFahey · 18th December 2012, 12:27 PM

Personal choice: although connecting all V- tabs through the sink is electrically the same as joining them through wires which anyway meet at the PSU, I never liked having a "hot" heatsink, even if inside an amp, at least because it complicates troubleshooting when (didn't say "if"

) one of the chips dies.
Besides, mica+grease added thermal resistance, although looks something good to avoid , is really not that significant.
But others may differ, of course.

Mark.Clappers · 18th December 2012, 12:44 PM

Quote:

Originally Posted by aadrian

Hi Mark.

yes in essence, the tabs will all be connected to the heatsink. Will this be a problem as long as the heatsink won't be connected with any other electrical element?

Most likely it won't be a problem, but be careful with "live" heatsinks, it bit me in the a** more then once when troubleshooting.. Also take really good care the power supply has an low impedance path to all TDA's (not via the heatsink) otherwise if 1 -Vs connection fails the current will be sourced via the other amps and the heatsink and most likely fry the leads of the other TDA's.

aadrian · 18th December 2012, 12:51 PM

all the TDA's are properly powered via sepparate wires directly from the source. the heatsink will not be used for powering purposes.

18th December 2012, 08:46 AM	#1
aadrian diyAudio Member Join Date: Dec 2012	Multiple TDA's sharing heatsink Hello all. This is my first post and I would like to start out with a question regarding sharing the same heatsink (large one) for 3 TDA7294 IC. The heatsink will not be connected to ground or any other wires. The box will be made out of wood so no connection to the box either. Is this ok or should I avoid sharing the same heatsink even if the size should be ok to handle the heat? Thanks

18th December 2012, 10:46 AM	#5
Mark.Clappers diyAudio Member Join Date: Jan 2010 Location: The Netherlands, near the German border	The tabs of the IC's are not insulated, so you would effectively be coupling the -Vs via the heatsink. If this is a problem is a different question altogether and can't be answered without more details of the complete setup. __________________ Music is art - Audio is psychoacoustics & engineering

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Sharing a Single Inductor for Multiple Passive LR Filters?	ryansupak	Analog Line Level	4	13th November 2012 09:32 PM
Multiple subwoofer/multiple amp question	boogs	Subwoofers	5	13th November 2007 04:36 AM
Non-Oversampling TDA's	supra	Digital Source	45	24th September 2004 06:56 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

18th December 2012, 09:48 AM	#2
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	Do bear in mind two things:- 1. Both ICs MUST be electrically insulated from the heatsink. 2. The heatsink is rated for a single source of heat at its thermal centre. If you mount two ICs away from the centre then the thermal performance of the heatsint will not be as effective - i.e. you will need a bigger heatsink. As long as you consider both these factors you can mount as many devices to the heatsink as you desire.

18th December 2012, 10:28 AM	#4
aadrian diyAudio Member Join Date: Dec 2012	thanks for the replies. Why should the ic's be insulated if the heatsink won't touch any other connection? what could occur?

18th December 2012, 10:51 AM	#6
aadrian diyAudio Member Join Date: Dec 2012	Hi Mark. yes in essence, the tabs will all be connected to the heatsink. Will this be a problem as long as the heatsink won't be connected with any other electrical element?

18th December 2012, 12:27 PM	#7
JMFahey diyAudio Member Join Date: Mar 2009 Location: Buenos Aires - Argentina	Personal choice: although connecting all V- tabs through the sink is electrically the same as joining them through wires which anyway meet at the PSU, I never liked having a "hot" heatsink, even if inside an amp, at least because it complicates troubleshooting when (didn't say "if" ) one of the chips dies. Besides, mica+grease added thermal resistance, although looks something good to avoid , is really not that significant. But others may differ, of course.

18th December 2012, 12:51 PM	#9
aadrian diyAudio Member Join Date: Dec 2012	all the TDA's are properly powered via sepparate wires directly from the source. the heatsink will not be used for powering purposes.