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Old 21st February 2012, 03:41 PM   #361
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Guys,

On the basis that I do an alternative layout for those who don't want to force cool, I would expect that the boards would be more than 'slicing the mosfets off each end.
In reallity to gain advantage the boards would need to be long with greater spacing between mosfets allowing a more even spread of heat along the length of the heatsink and thereby avoiding 'hot spots' which would be a problem if the mosfets remain at there current spacing.
Give me a couple of hours and I'll come up with some alternatives.
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Old 21st February 2012, 03:44 PM   #362
CeeVee is offline CeeVee  Portugal
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Quote:
Originally Posted by 6L6 View Post
Only 100 watt?

It's a class-A amp, so it's basically 25% efficient. 100 watts output will need 400 watts of dissipation... Per channel...

......

So, our worst-case scenario F5 v3 with 8 transistors per channel, and then 16 in a stereo chassis, you come up with 768in^2, or 5.3 square feet (1.6 square meters) of heatsink required.



So, a normal-looking, flat back heatsink, convection cooled is going to be staggeringly large. The heatsink profile will need to be much more complex. And probably fan-cooled.

Somebody please correct me if my back of the napkin calculations are incorrect.

It's more like 15% efficiency i think !

...I said it would be a beast....

When designing the board it looks easier than when you start juggling actual build options....
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Old 21st February 2012, 03:58 PM   #363
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it is 25%-40%ish. depending on if its SE or push-pull. push-pull is around 40%
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Old 21st February 2012, 04:07 PM   #364
CeeVee is offline CeeVee  Portugal
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...not as bad as i thought....glad to be wrong this time.
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Old 21st February 2012, 04:09 PM   #365
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...not as bad as i thought....glad to be wrong this time.
hehe
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Old 21st February 2012, 04:18 PM   #366
Horio is offline Horio  United States
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I am a big fan of the idea of separating the output boards and input boards. This would allow for people to make the standard SE build, mono-blocks and balanced cleanly. It sounds like there are a number of people (myself included) who are looking to do balanced builds, and a separate input board could be made to support a balanced option (probably would only need a few jumper locations). It also makes building mono-blocks more straight forward as well.

Separating the input and output boards would provide the maximum flexibility, at the expense of a little added cost. In the scheme of things, the added cost for the PCB's would be pretty insignificant.

My 2 cents.

Last edited by Horio; 21st February 2012 at 04:27 PM.
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Old 21st February 2012, 04:23 PM   #367
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6 of these, 3 on each side, ~15" deep stereo amp.
Good for 100W Class A, manufactured all over the world.

Do the crime, pay the fine.
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Old 21st February 2012, 04:23 PM   #368
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and you can easy get to the pots.
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Old 21st February 2012, 04:28 PM   #369
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so they are around 0.3C/W?
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Old 21st February 2012, 04:37 PM   #370
koja is offline koja  Canada
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Andy,
you cannot posibly cater to everybody's individual design, or the effort is going to fall apart.

That is why PDaniel makes the boards as small as possible, and then everybody can run wires to whatever an ideal mosfet location may be on their hsink. (only the holes for soldering nice size wire need to be provided).

p.s. for the same reason, I did not make an issue about no scoring lines and having to cut the boards for a V2 version to fit my heatsink; I am trying to live with the group choices (or else, if not possible, do my own pcb).
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