Heatsink approval needed for lm3886 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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
Reply
 
Thread Tools Search this Thread
Old 27th July 2007, 05:53 PM   #1
svbear is offline svbear  Canada
diyAudio Member
 
Join Date: Aug 2004
Location: Toronto
Default Heatsink approved needed for lm3886

Hi All,

I found someone selling these heatsinks.

The Dimensions are 15 & 1/10 inches long and 7 inches wide and the fins are about 5/8 inch tall.

I was thinking of using BrianGT's pcb boards with it, and having it lay horizontal as a top cover to the amp case.

Any opinions on if it's decent enough, and how many chips could I possibly run on it (with and without fan cooling on top).

Also, does anyone know if Brian's boards can be used with the lm3875 (with minor modifications).


Many Thanks Again,

Adrian
Attached Images
File Type: jpg heatsinka.jpg (24.4 KB, 619 views)
  Reply With Quote
Old 27th July 2007, 05:54 PM   #2
svbear is offline svbear  Canada
diyAudio Member
 
Join Date: Aug 2004
Location: Toronto
Different photo.
Attached Images
File Type: jpg heatsinkb.jpg (22.7 KB, 596 views)
  Reply With Quote
Old 27th July 2007, 10:07 PM   #3
svbear is offline svbear  Canada
diyAudio Member
 
Join Date: Aug 2004
Location: Toronto
Default Heatsink approval needed for lm3886.

Sorry Gents,

The title should say approval needed.

That's what I get for typing while on the phone at work.

So, would any of use this car amp heatsink for for chipamps?

Thanks,

Adrian
  Reply With Quote
Old 27th July 2007, 10:41 PM   #4
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
You could use that heatsink for at least a couple chip amps.
__________________
Brian
  Reply With Quote
Old 27th July 2007, 11:00 PM   #5
diyAudio Member
 
gtforme00's Avatar
 
Join Date: Oct 2004
You might want to read National's application note here: http://www.national.com/an/AN/AN-1192.pdf

But that's a lot to read to just say this. Based on AN-1192's suggested heatsink for the Bridged or Parallel LM3886's (see page 19 of AN-1192), I would say that the extrusion you are considering could take 2 chips for every 3 linear inches of heatsink (one on each thick part of the extrusion cross section I recommend). That's about 10 chips for the whole thing! If you are going to be using this in a hot environment or are going to be bridging/paralleling these you might want to err on the conservative side.

I personally have a similar heat sink and similar application and will be using 8 chips on mine. I wouldn't hesitate to add the other two if I needed them though.

Regards,
David
  Reply With Quote
Old 27th July 2007, 11:54 PM   #6
svbear is offline svbear  Canada
diyAudio Member
 
Join Date: Aug 2004
Location: Toronto
Cool.
Thanks guys. I was worried about the shallow fins, but it was designed for an old school rockford fosgate car amp, so I figured it must be something pretty decent.

He is selling them for $10, I was thinking of getting a couple.

He also has shorter ones, same design, same price.

I was thinking also of hunting down some black plexiglass for the front and back panels.

Adrian
  Reply With Quote
Old 27th July 2007, 11:58 PM   #7
Magura is offline Magura  Denmark
diyAudio Member
 
Magura's Avatar
 
Join Date: Oct 2003
Location: Denmark, Viborg
Quote:
Originally posted by svbear
Cool.
Thanks guys. I was worried about the shallow fins, but it was designed for an old school rockford fosgate car amp, so I figured it must be something pretty decent.

He is selling them for $10, I was thinking of getting a couple.

He also has shorter ones, same design, same price.

I was thinking also of hunting down some black plexiglass for the front and back panels.

Adrian

To make a couple of chipamps, all you need is one heatsink and a hack saw

I would guess that you could get by with at least cutting it in halves, maybe even in thirds...


Magura
__________________
Everything is possible....to do the impossible just takes a little while longer.
www.class-a-labs.com
  Reply With Quote
Old 28th July 2007, 12:22 AM   #8
diyAudio Member
 
gtforme00's Avatar
 
Join Date: Oct 2004
To answer your other question about the LM3875. I know that the 2876 is pin compatible, but don't have personal experience with the LM3875. A short trip to the National website reveals the following pinouts:
Click the image to open in full size.
Click the image to open in full size.

They don't look pin compatible to me. I would have to assume that it would be not be worth trying to use the LM3875 if you could help it.

Regards,

David
  Reply With Quote
Old 28th July 2007, 11:59 AM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
mute and ground are the incompatible pins.

Magura's hacksaw will do wonders for keeping the chips cooler.

Try cutting that tall heatsink into two shorter halves. It will dissipate about 40% more heat if the two halves are placed side by side.

Similarly if it were cut into 4 equal lengths it's dissipation capacity is just about doubled, compared to mouting all the devices on one giant heatsink.
One 3.7inch tall sink might just be able to cool a pair of chipamps, try fitting one first and see how cool/warm/hot it runs.
__________________
regards Andrew T.
  Reply With Quote
Old 28th July 2007, 07:44 PM   #10
pchw is offline pchw  United States
diyAudio Member
 
Join Date: Apr 2006
Location: Fremont, California
Hi Andrew,

Sorry for the stupid question, why cut the heat sink in halves will dissipate 40% more heat?

Thanks!!
__________________
- Fred -
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LM3886 Heatsink size? henkel Chip Amps 33 30th July 2012 03:45 PM
LM3886 Heatsink ormo Chip Amps 27 27th July 2009 04:15 AM
Required heatsink for 3 LM3886 in parallel? CJ900RR Chip Amps 7 2nd January 2009 05:19 PM
LM3886 & Others Chip Amp Heatsink Clamp Solution MartyM Chip Amps 7 18th October 2007 04:36 PM
LM3886 pcb approval wanted wxn Chip Amps 21 7th April 2005 04:56 PM


New To Site? Need Help?

All times are GMT. The time now is 02:57 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2