[G.Michael]

My cooling fan:



It's a quiet running 12VDC model, with, uhm, a sophisticated installation method.  I'm running it off a wall wart power supply with a resistor added in series to slow the fan so that there's basically a slight breeze blowing across the top of the amp. 

[Wayner]

There is another way to use the  muffin fan application. That would be to push the warm air generated by the tubes away from the amplifier, rather than push cool air onto the hot tubes. From my experiences at my other job, I know that upsetting homogenious temperatures can have bad consequences. The glass tube envelope (as all glass) likes to have a nice uniform temperature. If you induce a chill spot, there is a risk of rupture, due to temperature extremes. While G. Micheals fan technique looks OK, others may be blasting their tubes directly and I'm not sure that is a great idea. That is why I suggest placing a fan so that it draws the warm air to it an expells it away.

Wayner

[G.Michael]

That is why I suggest placing a fan so that it draws the warm air to it and expells it away.

I see your point, Wayner.  I am concerned that in my configuration, even with the fan mounted higher than the tubes, that one set of tubes will get more air flow than the other.  I'll turn the fan around, which probably will result in a more uniform air flow over the amp.  Thanks.

[JohnR]

My cooling fan:

I like it

[Niteshade]

Another suggestion: Keep your tubes polished. Grimy tubes do not dissipate heat well. Also- the longer that stuff bakes on them, the harder it is to get off.

[Wayner]

Oh yes, Nightshade has hit another nail on the head! Oils from your fingers can be removed from the quartz glass of the tube. I use rubbing alcohol to remove residue, and dude, have the amp shut off and cooled before you do this. All you need is a slightly wetted paper towel to wipe the tube surface. This is also a technique used on high powered lighting lamps (quartz).

Wayner

[jeenie67]

...after much annoyance from my Crown amp fans, I replaced them with ones from a computer supply firm and slowed them down with resistors. For my use (non-commercial application) the Crowns even at extreme Db never fade, and my Columbia tube power amp with two 6L6 tubes has it's own two whisper fans, also toned down, and it happily enjoys the breeze. No noise!....no hiss!...no buzzes!...nothing but cracking plaster.