If you're in the US, HeatsinkUSA offers many suitable profiles.
To determine the thermal resistance of the heat sink, I suggest reading the Thermal Design section of my Taming the LM3886 Chip Amp website.
Tom
To determine the thermal resistance of the heat sink, I suggest reading the Thermal Design section of my Taming the LM3886 Chip Amp website.
Tom
you will need a very very large heatsink plus fan cooling is recommended for this Power Amplifier IC ... something similar to the LM3875 i've build many years ago ... it will overheat fairly quickly if it is pushed hard and the heatsink is too small ...
Start with a heatsink at least 8inch wide x 4inch x 4inch with a fan cooling it should do well ...
Start with a heatsink at least 8inch wide x 4inch x 4inch with a fan cooling it should do well ...
you need to start with figure 22 of the datasheet.
you need your PSU voltage, your speaker impedance and the Ta in which the heatsink will operate.
Then I suggest you double the size of the sink to keep the chip cooler than the Tc=150degC that National assume.
Then double it again for two chipamps on a common heatsink.
That gives you the C/W for the sink. google that size.
You don't need fan cooling as long as your heat sink is large enough. I have four LM3886es - two on each side - of a chassis with heat sinks down the side. Works very well. At worst case dissipation (sine wave at half the rated output power), the heat sinks reach just shy of 40 ºC. That's very comfortable. The chassis is a BZ4309 from eBay.
As Andrew said, consult the data sheet (and my website). All the necessary information is there. Just do the math.
Tom
meh... just get 2 decent size older cpu heatsinks.
preferably amd heatsinks. they are designed for about 90 watt dissipation with the fan, keeping things under 70 celsius degree in normal ambient temperatures.
most likely you can get some at ANY nearby computer service for about ..
5 potatoes. drill 2 holes, polish it up a bit, and there you have it.
preferably amd heatsinks. they are designed for about 90 watt dissipation with the fan, keeping things under 70 celsius degree in normal ambient temperatures.
most likely you can get some at ANY nearby computer service for about ..
5 potatoes. drill 2 holes, polish it up a bit, and there you have it.
there are literal tonns of verry silent fans out there, 7812 + a few diodes in series is a pretty hack job but cuts them down to nearly inaudible level.
it does not need the fans on at all times, it can stay quite comfy without the fan, but its better to have them mounted and activate them if temps go high/the amp gets driven hard.
for 99% of time they will be off .
it does not need the fans on at all times, it can stay quite comfy without the fan, but its better to have them mounted and activate them if temps go high/the amp gets driven hard.
for 99% of time they will be off .
I like to be able to plug in a number and see the result. It helps me to understand,.. But the math is way over my head.
I ended up taking formulas from TI Data sheets, and formulas from Tom's website, and typed them into an Excel spreadsheet,.. Voila, I can see the results of various impedance speakers, power supplies, and ambient room temps. Made it real easy to understand my situation and choose an appropriate heat sink. HeatsinkUSA was prompt, easy to order, no problems.
I ended up taking formulas from TI Data sheets, and formulas from Tom's website, and typed them into an Excel spreadsheet,.. Voila, I can see the results of various impedance speakers, power supplies, and ambient room temps. Made it real easy to understand my situation and choose an appropriate heat sink. HeatsinkUSA was prompt, easy to order, no problems.
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