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In the Forum: Melquiades Amplifier
In the Thread: The short "6C33C Survival Guide".
Post Subject: Cooling the 6C33C amps.Posted by Romy the Cat on: 1/19/2010

Thanks, Paul.

My Googleised Chinese allowed me to understand that they use some kind of forced cooling but there was not mentioning of it. Upon further inspection I come across to this image:


So, the amp has two fans aside to cool this thing. I still very much do not like the design from cooling perspective. 4 of 6C33C within one inch from each is very insane amount of heat. It would be very high if they were the stand-alone 4 tubes but that are on the PC board surrounded with other components – that all will be roosted very soon.

The amp has 2 fans that I am sure take work as output fans. I think it is not only not enough but located at very wrong position. Take a look at the second image:


The hot air coming from the 4 x 6C33C chimneys is taking across the bank of power caps to the output fans. Even if they are high temperature caps then no caps will be able to a long time to serve in this condition. One 6C33C running at 50W heat up to 280 degrees Celsius, or 536 degrees Fahrenheit. 4 tubes in high proximity and confined space would do 300-330 degrees Celsius. So, the hot air blowing across those caps are in vicinity of 250 degrees Celsius – you might very much do not use those caps as in time they are not effective anymore.

In addition the side cooling in close proximity is a problem. When cooling air hit a tube from one side and another side is super-heated by another tube then it create not even cooling of glass that is very bad for tube. Doe this “bad for tube” has any practical impact? I do not know. I do not know if it affects sound. I am sure it affects the longetivety of the tube but who cares about it – in one year you need to trash 6C33C no matter what…. Still, I think this sided cooling is not too effective.

I understand that they were trying to make a compact and elegant design but it the elegance contradicts functionality then it is not elegance. I would like in this amp instead of moronic decorative gas to see a very powerful outtalking fan atop of the amp. The side, the top and any other vents shell be closed and the air shall be taking from the bottom of the amp. The outtalking fan I would make 18-20cm and would run it at relatively high 700-800rpm with thermostat. The circuit board I would redesign making a LOT of holes in it let air to pass across the circuit board.  I would even to make the amp 2-3 inches wider, letting the pairs of 6C33C to stay a bit further from each other. Perhaps it would be a good idea to list up the circuit board for 3 inches up and put the heat-sensitive elements under the bottom of the board…

The Cat

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