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Old 13th November 2006, 09:46 AM   #1
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Default Thermal management: it this not really of concern?

I've looked through the photo gallery and have been quite impressed with many of the gorgeous enclosures the members of this forum have constructed.

I've noticed, however, that very few of you have taken venting into consideration. All of those power resistors, high voltage caps, chokes - and in some cases - the valves themselves, are tucked underneath those beautiful boxes, leaving no space for their copious thermal discharge to escape. Sure, some of them have open bottoms, but I also know that you're a clever lot that is most likely aware of the aversion that heated gas has for downward travel.

I've been reading Morgan Jones' second book - Building Valve Amplifiers, and he puts quite a bit of emphasis on venting whenever possible.

Is the idea of keeping parts relatively cool simply in the interest of lengthening their life span, or would cooling also aid in keeping noise down and tolerances tight? Or, lastly, is extensive thermal engineering simply an unnecessary step that is only a consideration of the obsessive?

Fans make noise, so they're pretty much ruled out. Holes in the chassis may not be that ugly if placed strategially.

Adam
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Old 13th November 2006, 02:22 PM   #2
SY is offline SY  United States
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Quote:
Is the idea of keeping parts relatively cool simply in the interest of lengthening their life span, or would cooling also aid in keeping noise down and tolerances tight?
Yes.

A small computer fan run at reduced voltage can be very quiet. It doesn't take much air flow to make a significant impact.
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Old 13th November 2006, 02:50 PM   #3
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A good thread topic. I have routinely used plate load resistors that get hot, very hot, for example. Air needs to flow freely from below to above if no fan is used.

Quote:
It doesn't take much air flow to make a significant impact
A very valid point worth repeating now and again. There are diminishing cooling returns for increasing a fan's output flow (CFM). There can be a significant cooling effect from a slow (and quiet) fan.
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Old 13th November 2006, 05:54 PM   #4
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For some of my overly cramped and poorly ventilated amps, I use a small fan from a computer. These are made to work at 12 volts. I use a diode and a 1000uF cap on the 6.3 volt filament winding to get 7 or 8 volts. The fans run very quietly at this voltage.
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Old 13th November 2006, 06:04 PM   #5
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Using wood as my main material, my latest case has 3 vents on the top, which match 3 holes in the bottom, the heatsink inside is from the front to the back of the case and runs right underneath the line of holes... I have some round plastic vent grills that will go over the holes.

The wood has had 2 coats of Glatex 8, and after many hours of sanding is near glass smooth with no wood texture left...almost ready for the topcoat.

Want to try somethig similar for my Akido.
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Old 13th November 2006, 08:03 PM   #6
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OK - so it IS an issue that deserves consideration.

As a teenager, I had a part-time job building hot-rod PC's. With high-cycle CPU's and GPU's, cooling was always an issue and often demanded clever airflow designs to keep components stable. I'd even run a cloud of dense CO2 gas (dry ice + water) through the intake with a piece of plexiglass in place of the side cover to determine spots where the air wasn't flowing. Of course, this was probably over the top, but also fun and a great sales gimmick.

I still have oodles of CPU fans in my stash, so I'm sure I use some of them.

Has anyone noticed a SONIC difference when cooling is implemented?
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Old 13th November 2006, 08:15 PM   #7
anatech is offline anatech  Canada
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Heat will cause trouble down the road. Much like not getting your oil changed in a car. The damage is cumulative and widespread.

You really don't want to ignore this issue!

-Chris
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Old 14th November 2006, 12:39 AM   #8
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Quote:
Originally posted by LowRedMoon
As a teenager, I had a part-time job building hot-rod PC's
Geesh. As a teenager, four-function calculators hadn't even hit the scene yet. Now I'm feeling old...
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Old 14th November 2006, 02:31 AM   #9
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Quote:
Geesh. As a teenager, four-function calculators hadn't even hit the scene yet. Now I'm feeling old...
As a teenager I was building ------------ vacuum tube amplifiers.

Now 40 years later I am building ------- vacuum tube amplifiers.

We sold the Craig 4 function calculator in the stereo shop that I worked in, in 1972. It sold for $250 in 1972 dollars. Since the store was next to the University of Miami (expensive private school) we actually sold a few. At this time (I was 19) I was fixing vacuum tube (and solid state) amplifiers.

In between I built computers, starting in 1975. Due to lack of time, I just bought my first pre built desktop PC. The darn thing didn't work and now the pieces are scattered all over my workbench, and the tube amp is in the closet. I have now wasted a whole week finding a bad memory simm that passed memory tests for 6 straight hours, but caused random crashes and BSOD.

Tube amps or computers, all electronics are sensitive to heat. As the temperature rises the MTBF decreases. In a tube amp the electrolytic caps, and resistors, and the tubes themselves are the most affected components. The hotter they are the shorter they will live. I have not noticed any sonic differences, but resistors (and semiconductors) will be noisier as the temperature rises.
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Old 14th November 2006, 02:46 AM   #10
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Did you happen to notice "Morgans" own prototype was way too cramped on the chassis....bad for heat management.
Perhaps thats' why he put the "Make the chassis big enough" in BOLD type.
________________________________Rick...........
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