Contest: Linear Power Amp in a mint tin (class Aa, class AB, or class B) - Page 21 - diyAudio
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Old 19th January 2013, 02:47 PM   #201
JMFahey is offline JMFahey  Argentina
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Cool !!!!
Problem will be to pull heat out, but hope you solve it.
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Old 19th January 2013, 03:08 PM   #202
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Not being a participant in this contest I am still following it as it looks so interesting once a final circuit is designed. It appears that one of the most important aspects of this design is going to be the dissipation of heat. While I imagine what Jack has shown with the thin aluminum plate will help that seems to be more a heat spreader than a proper heat dissipation method. If I was approaching this as a design project I would be looking at some type of sculpted heat sink that could be fit internally that would allow for a higher heat transfer surface area and some well thought out cooling venting to allow the heat to escape. If I can get some time I may draw up a CAD design that could be used internal to the tin can. An alternative method may be the application of a heat pipe to pull some of the heat out of the inside of the tin. Are the rules such that nothing can protrude from the tin, or is this an option?
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Old 19th January 2013, 03:49 PM   #203
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The tin of itself has a thermal impedance of ~5.5 C/W -- if the chassis is mounted vertically and the bottom portion of the tin cut (nibbled) out and the remaining portion of the tin riveted to the aluminum plate it should be adequate for a 10W Class AB amplifier.

With only +/- 17V, however, I don't know if the 4702 will allow THD% below 0.010% The LT1166 will, but would require more real estate even though it's an SOIC chip.
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Old 19th January 2013, 06:10 PM   #204
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If that substrate were copper you'd have a ground plane!
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Old 19th January 2013, 07:32 PM   #205
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jackinnj! Go for it!
Make it Class-B or something close and you will be fine.
PS voltage 20+/-...
Definitely a winner here.

Last edited by palstanturhin; 19th January 2013 at 07:34 PM.
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Old 19th January 2013, 07:47 PM   #206
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I'll put the output devices on the aluminum and put a piece of pcb material for the 4702 -- that way it can be done manhattan style.
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Old 19th January 2013, 08:52 PM   #207
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Well, there's capacitors in the mint tin, so I've been recommending "feet" of at least 1/2cm tall and air intake holes in the bottom of the tin and air output holes at near the top of the tin (perhaps around the lid's rim could be decorous). Hot air wants to go up, and if allowed to do that, it will make a hasty exit, voluntarily. This moves replacement, cool, air in through the bottomside intake vents, voluntarily.

Since the main concern is the capacitors, and I think that we'd probably like to put air intake vents underneath All of the capacitors. Some PCB efforts may need additional vias/holes to allow cool air to rise up near capacitors (anti-heat-pooling design).

I like the thin aluminum bar stock thermal pasted to the bottom of the mint tin (to put heat out of the mint tin); but, I do still believe that the location of intake vents is simply more important at capacitors.
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Last edited by danielwritesbac; 19th January 2013 at 09:00 PM.
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