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Old 13th July 2003, 01:17 PM   #1
Gunders is offline Gunders  Norway
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Default Cooling of Vacuum Tubes

What advantages would cooling of tubes have?
My first thought is about noise, Would it cause less noise?
How can I cool down the tubes?
I have thought about drilling some holes in the chassie near the tubesockets and use some fans,
this is probably the simplest method.
Other thoughts is about using some kind of heatspreaders at the tubes, maybe they can then also functions as shields.
A more advanced method would be to use some kind of liquid, this liquid has to be circulated through some pipes which are coupled to the tubes.

I have heard very little about cooling of tubes, in fact the only thing I have heard was about a mic amp for pro use who used some kind of liquid cooling.
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Old 13th July 2003, 01:36 PM   #2
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Hi,

TUBE COOLERS.

Several industrial tubes use cooling in various forms such as forced aircooling, oil cooling etc.

EIMAC.

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Old 13th July 2003, 01:48 PM   #3
EC8010 is offline EC8010  United Kingdom
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Cooling a valve reduces noise. A Sony microphone used Peltier effect cooling. The problem is that the glass envelope isn't very round or consistent unless specially specified, making it difficult to obtain good thermal contact. One way around the problem would be to suspend the valve upside down in a finned bath of oil.

Fans are noisy. Even the quiet ones. Nevertheless, pointing a fan at a valve cools it quite effectively.
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Old 13th July 2003, 01:50 PM   #4
Gunders is offline Gunders  Norway
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Thanks.. very interesting...

I didn't mention that I'm aware of that transmitting tubes usually use some kind of cooling, mostly forced air or water circulation.
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Old 13th July 2003, 02:13 PM   #5
EC8010 is offline EC8010  United Kingdom
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The biggest ones use steam.
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Old 13th July 2003, 02:18 PM   #6
Gunders is offline Gunders  Norway
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steam?
How can steam be used for cooling?
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Old 13th July 2003, 02:25 PM   #7
EC8010 is offline EC8010  United Kingdom
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Default Latent heat of vapourisation

I thought that would surprise you! It takes six times the energy to convert water at 100C to steam at 100C as it takes to heat the same mass from 20C to 100C.
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Old 13th July 2003, 10:48 PM   #8
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It's called phase transition cooling, or something like that.. obviously you can't use hard water

A lot of big tubes are spec'd for water and forced air cooling: water for the anode, air to keep the pin seals cool (e.g. heater).

Tim (has a 4X150A and a pair of 4CX250R)
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Old 14th July 2003, 06:48 AM   #9
SHiFTY is offline SHiFTY  New Zealand
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If you are designing from scratch, choose tubes that don't run too hot, ie 6V6 instead of EL84, 6550 instead of EL34 etc. The bigger the glass envelope the more surface area and better cooling, i guess.

Most tubes seem to run fine in free air unless you have a high ambient temperature. Norway is about the same as NZ so you are ok

As for reduced noise, have you heard how loud computer fans are? They suck, I think any decent music system should be fanless.

But good ventilation is a great idea, I try and recess my tubes into the chassis a little to get airflow around them, the so called "chimney effect". Keeps them cooler.
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Old 14th July 2003, 07:20 AM   #10
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Quote:
Originally posted by fdegrove
TUBE COOLERS
Made commercially by Pearl HiFi, they are available at least at in Parts Connexion NA & Moth Audio in the UK. They are cheap enuff that one has to have 2nd thots about DIYing them.

Bill has an article on them.

Click the image to open in full size.

dave
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