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Cooling fans for tube amp

Just read a thread from 2005 about rack cooling fans. I'm having a custom built wood cabinet made with casters for my stack that includes an Audio Research D-90 that can get very warm after an hour or so.

Any new recommendations on what fan to use and how to set-up? Most computer fans don't have standard wall plug connectors.

I was thinking about a 4" diameter fan that will plug into my "Switched" power output off the SP-12 pre amp so it goes on auto whenever I power up. Should it "push" or "pull" the air? Mount on the back of the cabinet with a cut-out for airflow?

I may just run a power strip off the pre-amp's switched output to power one to two fans plus the subwoofer so they all only run when I power up the pre-amp and amp.

Also thinking of putting heat resistant tape/insulation on the underside of the wooden shelf directly above the amp.

Sound OK?

Or something better work w/o a major engineering project?
jamesk58
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ssvlaunch
27 posts
 
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.
bmcleod's avatar
bmcleod
57 posts
 
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.
jamesk58 OP
73 posts
 
My plan is to get the 4" fan and mount on the back side of the cabinet. The cabinet does not have doors. There is a 3" circular hole perfectly situated in the 3" space above the top of the amp and the next shelf.

The fan should pull ambient air from the front of the cabinet across the top of the amp and out the back. I will also look into a reostat so I can modulate the air flow.
inpepinnovations1e75
395 posts
 
Again, induced or forced draft doesn't change the amount of air cooling the tubes nor its quality. Even if the pressure is positive inside the cabinet, dust enters from the room in the air being blown in by the fan, unless one has a filter on the intake of the fan.
At any rate, the tube amplifier should not be placed inside a cabinet and if one must, it should be placed at the highest level so that its heat doesn't affect other components.
audiofeil
4,011 posts
 
Good planning Jamesk58. You're doing it correctly.

Have fun.
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