Cooling fans for tube amp

Forced draft or induced draft, it doesn't matter, the tubes don't know whether the air is being 'pushed' at them or 'pulled' by them. Usually, however, one can get more air flow for the same size fan in a forced air setup, but the difference isn't much nor critical. I see only noise problems using a combination of forced and induced draft and no advantages.

Salut, Bob P.

Hot air should be drawn away from tubes not cool air blown on them.

Thank you.

Well I just got the cabinet and set the equipment up. Everything is working great, but yes the underside of the shelf directly above the amp is hot as a skillet. Still thinking of getting some automotive heat tape for the underside of the shelf just to protect it and get the RS 4" fan to pull the air out of the lower part of the cabinet.

I had them drill three 3" holes spaced equally from top to bottom. I'm running cords/wires out of the top two and left the bottom one unused for the fan.

For now I think I'll plug the fan to the switched power strip I set up off the pre-amp so it will run as long as everything else is under power.

I have dealt with all the problems mentioned above and had one more. I live in the mountains in southern California and in the summer it's gets a bit dusty. I realized that by using two 12 volt fans to exhaust the air out of my cabinet I was creating a negative pressure situation. This was drawing dust in through the doors and other joints. By installing the fans to blow into the cabinet you can create a positive pressure and keep dust from coming in all the cracks and joints. I also made a small metal box for the intake which I keep a piece of washable air filter material in to prevent dust from being forced into the cabinet. Everyone is correct when they stated that you don't want to blow air directly onto a tube unit. I just located them where they don't blow directly on anything. The static pressure inside the cabinet and the leakage though all the doors etc, seems to keep things flowing nicely and everything stays cool and dust free.

I stand by my statement, you want to move air through the cabinet and heat away from the equipment. You need a source for the air (vents or an input fan) and a place to exhaust the air (vents or an exhaust fan). You can do this without "blowing air on the tubes" (if you think that's a problem), but some may not be able to visualize this.