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bencat

Do Valve Power Amplifiers dissipate heat better without a cover ?

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Super Wammer

This is a question which I would like to find some evidence of. I am using a Croft 4E loaned amplifier and it sounds very good indeed. At some stage this is going to be replaced by a Croft OTL power amp . The 4E produces quite a large amount of heat which is expected but despite there being a very good gap (over 5 inches ) to the next shelf it is still capable of making that shelf quite hot .

Would removing the metal cage cover and running the amp with the valves on show improve the air flow and let the general heat dissapate easier ? As I have no children at home anymore and i learned many years ago no to stick my finger into a running valve amp I am not too worried about open nature of the unit . What I would just like to do is reduce the  centralised nature of the heat build up.

So any views , facts or even just speculation ?

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Its fine to run them without a cover but this may increase heat buildup on the upper shelf as convection is increased. 

If you aren't afraid of appearances fitting an 80 or 120mm 'silent' computer fan to draw the air through the amp will have much much more impact and can be oriented to lose the heat sensibly. They are cheap and tend to run off cheap power supplies - an old ATX PSU from an ancient computer will be way more that you need. 

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Super Wammer

Thanks Jazid , will give that a little thought as my technical skills are not that good .

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Super Wammer

@bencat The OTL3 does run hot, saves on heating in the winter :) . Because of its size, I do not have a rack large enough for it, so it used to stand on a piece of granite next to the rack. I do have a Unison Research S4 in a rack, and that again dissipates a lot of heat without a cover, so not sure taking the cover off will help . Also remember the OTL valves have a top connection wire too.

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Posted (edited)

I had a similar situation with a 300B amp about 2in away from the shelf above. These are wood and were getting quite hot. So I screwed an aluminium plate to the shelf over the valves. I spaced it away about  5mm from the shelf to leave an air gap, Been there a couple of years now

Edited by zeta4

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Posted (edited)

I would have thought there will be better heat dissipation but as someone says above that will increase the heat the shelf above sees. My solution with my Cary 805cs is to bring them forward on the shelf so the 845 output valve clears the shelf above. It didnt fall forward with the 'moment' because its a long amp and the massive amount of 'iron' is to the rear of the amp providing counterbalance. (I'm not able to put them on the floor due to lack of space.) In your case with the Croft a brick or similar might do the counterbalancing job . Obviously you would need a sub shelf of suitable proportions.

Incidentally, my Carys have an aftermarket internal fan fitted by the previous owner (Farflungstar) to cool the electronics. But then he lived in Spain.

Re the fan idea why not pm Speedracer who has rigged one up behind his rack?

Jack

Edited by Non-Smoking Man
sp.

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To expand on what was said earlier, If you think about conservation of energy then initially the cage will warm up taking that energy but once it reaches steady state the energy coming in will equal the energy going out so no reduction in heat output. However what it will do is distribute the convection energy over a wider area, thus the heat of the shelf above will be more evenly distributed than just above the valves, which is better.

Whether this really matters depends on how hot the upper shelf gets and if it has an effect on what is on that shelf (eg rubber feet or another hot amp).

As also said above, a fan to push that convection heat away from the rack and into the room (rather than towards a close wall) is the best option.



Sent from my HRY-LX1 using Tapatalk

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Super Wammer
2 hours ago, Speedskater said:

There is an increased risk factor to others who don't understand the dangers.

Not sure what exactly you are referring to here ? Risk because there are exposed valves ?

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Moderator
35 minutes ago, Speedskater said:

Risks:

  • burns from valves
  • exposed high voltage
  • broken valves by children or the cleaning staff.

One's butler is properly trained in the correct methods to remove dust from valve amplifiers and the housemaids only undertake cleaning duties on the lower floors of the residence.

  • Haha 1

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Super Wammer
On 24/06/2020 at 00:13, Speedskater said:

Risks:

  • burns from valves
  • exposed high voltage
  • broken valves by children or the cleaning staff.

Retired and live with just myself and my wife so no problems to children . Both Linda and I recognize the danger of getting burnt by exposed valves ran piar of Quad II,s for quite a few years so not issues there . Dust , dust you say sorry my OCD will not let that happen . No one will touch this but me so nothing you have listed is worrying me . As @rabskisays ones staff are fully trained regarding the importance and delicacy of one's equipment.

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