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Old 11th December 2006, 07:13 PM   #1
sts9fan is offline sts9fan  United States
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Default 2 sinks per channel for Zv9?

I am making a pair of Zv9 monoblocks and was wondering if it is possible to split the load onto two sinks? Could this be done by attaching the board to a copper plate and putting that half on each sink? If I was to do this how is the heat dissipation effected?
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Old 11th December 2006, 07:17 PM   #2
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You can use as many sinks as you like, and there is no
requirement that they be tied together (unless there is more
than one sink per transistor

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Old 11th December 2006, 07:26 PM   #3
sts9fan is offline sts9fan  United States
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Thanks for the quick reply!

So if I two transistors on each sink I will have no problems? What is the best way to figure out how much heat I need to dissipate per transistor?
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Old 13th December 2006, 12:12 PM   #4
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I'm normally a tube guy (and no, I'm not very good at that either), but I needed to know how much to dissipate per transistor for the F2 design and not surprisingly, I had no freaking idea.

So, I did a little research online and came up with the attached spreadsheet (which I'm still not sure is correct, by the way so maybe a little help here?) and I think this should get you in the ballpark (see earlier parenthetic disclaimer about verification, though).

Anything highlighted in green, you need to flll in and it goes like this:

Power: The power (W) to dissipate per heatsink.
Max Tj: Get this from the transistor datasheet (maximum junction temperature).
Ta: Amibient termperature (I used ~30C).
Jc: Get this from the datasheet (junction-to-case thermal resistance).
Cs: Thermal resistance of any heatsink paste / SILPad, etc. (I just used .1 as suggested in the article I read).
Ja: Get this from the datasheet (junction-to-ambient thermal resistance, I think).

Heatsink Thermal Resistance (Sa): This is the thermal resistance of the chosen heatsink, if you know if. If not, there's a link to an online calculator in another F2 post that's really helpful.

The rest calculates itself and there's two calculations. The first is based on the thermal resistance requirements vs. the rating of the heatsink. The second is the total estimated temperature of the heatsinks in action vs. the maximum temperature rating of the transistor, which is hopefully close to how hot the sinks will get.

OK-- here's the boldface disclaimer as backup:

Kofi Annan is generally regarding in the DIYAudio community as a dumbass. This means that any reliance on anything he says could be potentially dangerous or deadly to you, your family, your dog, your neighbor's dog, your state / province / reservation or your nation. Please, please, for God's sake, please double-check everyything he says. Just look at some of the stuff he says, will ya? It's nuts.


Anyway, the reason I'm posting this is because it's time for me to try and give instead of takingtakingtaking all the time. I'm ready to hear why this is wrong and correct it, so please, comments, criticism and outright assault is welcome.

Yours in incompetance,
Attached Files
File Type: zip heatsink calculator.xls.zip (3.2 KB, 52 views)
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Old 13th December 2006, 07:13 PM   #5
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To prevent shock hazard, do not operate Kofi Annan out of doors,
in the bathtub or shower. If you spill liquid in Kofi Annan,
contact an authorized service facility.

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