Fan Cooling System for a Guitar Tube Amplifier




Introduction: Fan Cooling System for a Guitar Tube Amplifier

About: Journeyman electrician, Musician, woodworker, and Inventor.

This Instructable will show you how to make a
fan cooling system for your guitar/bass tube amplifier.
*This instructable requires electrical/electronics/woodworking tools and knowledge.*


If you can't or don't want to make one for your self,
I soon will have them available at...

Step 1: Fan Cooling System (pics of On/off Temperatures)

This is a Fan Cooling System for a guitar/bass tube amplifier.
The Idea behind this instructable is that  tube amplifiers get very HOT!
I understand that Hot tubes=Great tone!!
Although heat can kill an amplifier.
If your power transformer gets to hot, it will cost about $100 to replace,
heat will kill your capacitors in the amplifier killing your tone, and be costly to repair,
If the temp gets to hot inside the cabinet you speaker could blow, it will cost $50 or more!
So this system can keep your amp cool and save you money!!!

I have ran many tests with this system on many different amplifiers,
on average a power transformer gets to 120deg. or more,
with My fan cooling system the temp drops to about 70deg.

Step 2: Tools and Materials Required

tape measure, pencil
drill, small drill bit, 2" hole saw
table saw or circular saw?
clamps, wood file, sand paper
razor knife, and paint brush
24" x 24" x 1/4" thick plywood
computer fan, electronic on/off switch, 9v battery, clip, and connector
2- 8-32 screws with washers and lock nuts,
electrical tape, U/L list metal duct tape, black paint

Step 3: Measure the Back Panle

To make the back panel for this fan cooling system,
you need to measure the inside of your amplifier cabinet
edge to edge, and about 1/2" down past the tubes

or you could use the existing panel cover
that came with your amplifier this also makes
a great template for the tube vent hole that has to be cut out.

Step 4: Measure and Drill the Mounting Holes

Measure and drill for the back panel mounting holes,
if you have the original back panel use it as a template.

I line up the panel top to bottom and side to side
make my marks, and drill*

*I drill them out a little bit bigger so that the New back panel install easily.

Step 5: Measure for the Fan to Be Installed

Typically in the Left corner of the amplifier chassis is the location of the power
transformer, the center of this location is where you want to place the fan for the cooling system.
after you have this measurement transfer it to the panel board that you cut in step 2
Make sure the fan is in the correct location and trace it with a pencil,
now use a small drill bit to mark the location of the mounting screw holes on the computer fan
remove the computer fan and drill the mounting holes and drill the fan hole with a  2" hole saw*
*(may be larger or smaller depending upon fan size?)

Step 6: Measure and Cut for the Tube Vent Hole

Measure the center point of the tubes coming down and 1/2" to the left and right
transfer this to the back panel, use a 1" hole saw to cut the ends out and then
use a strait edge to make a line connecting the outside edges of the circles.

if you have the original back panel you can trace the vent hole to your back panel
and cut out with a scroll saw

Step 7: Heat Shielding

Install U/L listed Heat Shielding metal tape to the inside of the back panel
I cut strips longer than the panel and overlay them and double them up on each strip.
Then flip the panel over and cut out with a razor knife the fan hole, use a drill bit for the
back panel mounting screw holes.


Step 8: Painting the Back Panel

Now you are ready to Paint the Back Panel for your amplifier cooling system.
If your amplifier is covered in black tolex you can simply paint the panel black,
or you can cover it with a piece of black tolex material.

If your amplifier is covered in tweed you can simply paint the panel brown,
or cover it with a piece of tweed material.

I have  Tolex and Tweed available threw my website...

Step 9: Installing the Electronics

Now that the back panel is complete, it is time to install all of the electronics
that make this fan cooling system work.
first install the computer fan with the 8/32 screws, washers, and lock nuts.
then drill a hole an 1 1/2" down past the chassis, for the fan wires so the fan wires
can enter the back side of the panel.
also drill a 3/16" hole for the on/off switch. ( this could be done before the Painting Step?)
and drill a hole for the battery clip located a the bottom corner of the panel.



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    17 Discussions

    This is me thinking too much, even though I know the answer already, but is the fan venting air out of the chassis or pulling fresh air into the chassis to cool the tubes?

    That's a really nice job, two questions:
    Could you fit the fan on the inside?
    Are these things then badly designed in the first place, or just "cheap"?


    7 replies

    I would NOT install the fan inside the chassis,
    there is way to much power in there to mess around!
    To say amps are badly designed? I say Yes and No,
    Tube amp circuits get Hot it is a fact,
    amp manufactures suggest placing a fan on your amp to keep it cool?
    I have had power trans, caps, and other parts burn up because of heat.
    With the fan cooling the trans, and circulating air in the cabinet,
    I have Not had a problem in years!

    Fitting the fan inside was a space consideration, I don't quite get the "there is way to much power in there to mess around!".
    Do tube-amps sometimes come with fans, is yours one that just didn't?


    The Fan Only extends about a 1/2",
    for this instructable and liability reasons I kept it low voltage, and
    isolated from the chassis and High Voltage circuitry.
    The fan is cooling the power trans. (120v) that feeds 450v caps.
    There is No tube combo amplifier with a built in fan?
    Rack power amps have them built in like a computer does.
    Nothing like this is available.

    Patent Pend.

    thanks again!

    Yes you are correct, the peavey classic 50 has a cooling fan built in,
    this was designed for the application and is UL tested and listed.

    Thanks I knew if something like this was already out there the experts
    here at instructables would find it and let me know?

    could you not put the electronics of the fan in a plastic case inside the cab, thus allowing you to store the fan inside

    Umm, I doubt anyone can completely know about electricity and guitar tube amplification, I think a basic understanding would be good enough.

    2 replies

    I did Not mean completely, my point is if you don't understand electricity
    within a tube amplifier, DON"T attempt to make this instructable!

    I see a lot of crazy people on here when it comes to electricity?

    Just a basic understanding of electricity is what gets people killed!!

    Great! Top marks here.

    I'm rebuilding an old Kalamazoo Bass 30, and using it a lot for guitar. But it's very poorly ventilated. So I've been planing on adding the fan.

    My only concern is something you don't mention--noise. How did you choose the fan, and did you test different fans? Were there any noise issues after the installation?

    4 replies

    Ah, now I notice it's battery operated, so at least it's electrically isolated. Still, RPMs would cycle in the audible range, I should think.

    No problems, though?

    I'd want something that would run off the same mains connection.

    I  have never wired one into the mains,
    I know it can be done though, filter caps might block noise?
    My personal amplifier I hard wire the amp to an outlet plug,
    installed inside the cabinet for pedal power packs,
    and have Not had any issues with noise?

    Thank you very much!
    Because it is Battery operated there is NO Noise?
    I have made a few with different types of fans, there all about the same?
    The only time there was any noise is when you use a poor quality
    wall transformer to power the fan.