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Old 4th December 2005, 05:37 PM   #1
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Join Date: Dec 2004
Location: Bakersfield, CA
Default Heatsinks and Insulators

Hello,

I am building my first LM4780 chip amp. I am building a servo BPA200 straight from the application notes as provided by National. I have two issues.

#1) I am having a hard time finding a good source of heatsinks. Conrad Heatsinks out of Australia has exactly what I am looking for in their MF15-100 product. However I live in near LA, California and the shipping would probably exceed the cost of the heatsinks! Does anybody have a good US source for heatsinks??

#2) The LM4780 packaging is attached to the +V rail. I want to physically make the heatsink mount external to the cabinet, which means I need to electrically isolate the chip amp from the heatsink. Problem is I cannot find a source for TA27 package insulators! Can somebody please point me to source?

What are people doing here for heatsinks and insulators??

Thanks in advance,
Carl Huff
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Old 4th December 2005, 08:30 PM   #2
ArtiomR is offline ArtiomR  Lithuania
diyAudio Member
 
Join Date: Jan 2005
Location: Vilnius
Hi, Carl!

After some hours of frustrating search for my next amp's heatsinks I've found these GlacialTech PC coolers: Click the image to open in full size.
Igloo 7200
I've stopped at these, because they are cheap(around 7$ where I live), they are Black, it helps to radiate heat, and they are "square" so it's easy to mount them to the chassis.
I'm going to cool my LM3886's with these.
Just like you, I'm going to put put them ouside of the case with fans unscrewed, and maybe I'll bend the blades to the sides for better cooling: \\||//

And here is what I'm going to use as insulation (ALO-P3-3) :
Click the image to open in full size.
Here is what www.elfa.se says:
Quote:
Mfr. Austerlitz
Aluminium oxide washers have a significantly lower thermal resistance than both mica, kapton and silicone rubber. The insulation voltage is also lower. Thickness: 3 mm for ALO-3 and ALO-P3-3, and 1.5 mm for ALO- 220.
Thermal resistance: <0.3 /W
Isolation voltage: 30 kV
Temperature resistance: >400 C
Or you can just use mica washers, which are quite common and are usually recommended.
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Old 4th December 2005, 09:07 PM   #3
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Join Date: Sep 2005
Location: Melbourne Florida
Default heat sinks and insulators

www.thermaflo.com
www.psiextrusions.com
www.aavidthermalloy.com
raw materials, www.onlinemetals.com for copper bar aluminum ect....
You can use TO3AP flat pack insulators in either mica or teflon just use them sideways and trim of original mounting hole and cut a new one.
Have you thought about not useing the servos?? I tried the servo BPA200 sounds terrible! very hollow compressed no bandwidth ect....
Useing .1% resistors in the feedback loop and 1% output resistors along with a 47uf tantulum cap 10% tolerance 16V will work for decoupling will offer very good results and is a much more simple circuit. Keep paths short, run a ground plane and make sure no DC on input.
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Old 5th December 2005, 06:13 AM   #4
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Join Date: Dec 2004
Location: Bakersfield, CA
Geez,

The servo version sounded that bad?? I would have thought that it should have sounded better, not worse. The non servo version is much easier to build. I'll give that a twirl instead.

Thanks,
Carl Huff
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