oneplustwo F5 build thread - Page 4 - diyAudio
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 18th February 2012, 02:12 AM #31 diyAudio Member     Join Date: Apr 2009 Location: San Francisco One other detail, there are 37 2" fins and the overall size is 11.5"x5". Seems to be a good match based on what NP specifies in the manual (his example is 8"x6" with 2" fins at 0.6 C/W.)
 18th February 2012, 02:25 AM #32 diyAudio Member   Join Date: Feb 2009 pr. device. total of 4 pc.
 18th February 2012, 02:40 AM #33 diyAudio Member     Join Date: Apr 2009 Location: San Francisco Hmm... Uh oh. Did not catch that critical detail. But if I do my math... 0.6 C/W/" with 5" long heat sink = 3.0 C/W. At idle, 62 watts divided by 3.0 is just over 20 C which is what I was aiming for. Is there a mistake in my reasoning or am I good to go? -J
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Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Quote:
 Originally Posted by oneplustwo Hmm... Uh oh. Did not catch that critical detail. But if I do my math... 0.6 C/W/" with 5" long heat sink = 3.0 C/W. At idle, 62 watts divided by 3.0 is just over 20 C which is what I was aiming for. Is there a mistake in my reasoning or am I good to go? -J
My guess is that the Antek rating of .6 C/W is for that particular dimension heatsink, and the calculation should be dT(C) = .6 C/W * 62 = 37.2 C temperature rise above ambient.

Here is a useful resource about heatsinks: ESP - Heatsink design and transistor mounting.

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Join Date: Feb 2009
Quote:
 Originally Posted by oneplustwo Hmm... Uh oh. Did not catch that critical detail. But if I do my math... 0.6 C/W/" with 5" long heat sink = 3.0 C/W. At idle, 62 watts divided by 3.0 is just over 20 C which is what I was aiming for. Is there a mistake in my reasoning or am I good to go? -J
standar F5 like to see 0.3C/W. 65W/25C=0.38C/W.

 18th February 2012, 04:40 AM #36 diyAudio Member   Join Date: Mar 2010 Location: Olalla, Oregon: Land of the 100 Valleys I have used this thermal simulator for evaluating heatsink designs. It it capable of dealing with discrete heat sources so that MOSFET placement can be optimized. Frigus Primore - Thermal Design for Electronics
 18th February 2012, 04:46 AM #37 diyAudio Member     Join Date: Apr 2009 Location: San Francisco Wow, my math sucks after being out of school for so long. Couldn't even properly keep track of the units. I will say, Antek claims it can dissipate up to 150W/channel so I have that going for me. Thanks for the resources, I'll do some reading. Ultimately, I'll probably just try it as is and see how much rise I get with an actual measurement. Last edited by oneplustwo; 18th February 2012 at 04:55 AM.
 18th February 2012, 05:26 AM #38 diyAudio Member   Join Date: Feb 2008 Location: Jackson,michigan I believe (although I am still learning about heatsink's myself) if the material is rated at .6 C/W per inch then your 5 inches of heatsink material should be rated at .6/5= .12 C/W. At 180 watts of dissipation the heatsink will be 180*.12= 21.6 degrees celsius above the ambient Temperature. This seems to be just about right. If I am wrong about this please somebody jump in here and correct me on this !!! I have been scoping out heatsink's for my build and I have been thinking of using some Ximatec CPU coolers. http://www.newegg.com/Product/Produc...82E16835233082 For \$30 this one is rated at .15 C/W at least and is fairly quiet with a fan at 16-24 dba. XIGMATEK One of these will allow 333 watts of dissipation at temperature rise of 50 degrees celsius. It maybe a bit on the warm side with a total heatsink temp. of 75 degrees celsius. But, It is still below the safe limit for the devices as long as the heat pipe don't explode. It is not uncommon for these to be run at levels of 200 watts or so. I am considering about 2 to 4 of these would be good per channel for a Turbo F5 build. I will mount these to a thick aluminium or copper bar heat spreader to mount the output devices to. I am anxious to see how your build turns out. The only thing holding me back right now is were to source the JFET's so I don't end up paying so much for the shipping for just a few pieces. Keep on DIYin' jer
 18th February 2012, 05:33 AM #39 diyAudio Member     Join Date: Apr 2009 Location: San Francisco Yes, that's how I recalculated as well but it seemed too good to be true. Perhaps it's not a linear relationship? With every additional inch, you get less benefit. We'll see!
 18th February 2012, 05:46 AM #40 diyAudio Member   Join Date: Feb 2008 Location: Jackson,michigan Here are a few more links to some more heatsink calculators that I found awhile back, HEATSINK QUESTION Enjoy !!! jer

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