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?
This place has a nice variety of units. Most have thermisters that turn the fan on automatically when it gets warm so you just leave them plugged in all the time. I have a pair on my HT amp that do a good job and are pretty quiet, but I can slightly hear them when nothing's playing. Or better yet find some nice wood grills and "open up" the sides of the cabinets so you don't need the fans.
Radio shack sells Fans that you can mount easily, they are not noisey, and you can add a standard plug to them pretty easily, I did this a long time ago when I had a receiver in a cabinet which would turn on with the switched outlet on the receiver like you are saying. I would mount one probably sucking the Air out of the cabinet, so your not shooting the air at the amps, but pulling it out of the cabinet and shooting it out the back or something would probably be more effective, removing the hot air. Computers are set up this way as well.
Thanks Bmcleod, I'll check them out.
If u are somewhat of DIY (can u use a screw driver and electrical tape? ...:)): You might want to check out...good old RadioShack. I bought a fan, wired for connection to regular 110v (comes stripped wires - you'll need to connect wired standard plug -looks like the one on the site the previous response pointed to). It's relatively quite - I installed / mounted it on the back of my cabinet (cut an opening if it's not there already) and it keeps my tube equipment and the wood cabinet cool. It does very good job at that to the extent that even though I had planed to install a metal sheet on the top to prevent the heat from damaging the cabinet - it seems that I don't need to do it. I can hear the fan, up close, if the doors are open and there is no music playing. Hope this helps.
Ahal1, has it right, thats exactly the one I am talking about.
Parasound makes an audio cooling unit called the Zbreeze you may want to check out, if you're non-DIY (like me).
Ahall, FWIW on a 110v fan you can probably add a rheostat and reduce the speed of the fan to a point where you will not hear it at all and you will also minimize any vibrations it would transmit (at full speed) into the cabinet. At least these were problems I experienced and that is how I solved them. FWIW.
Thanks guys. I did check out a RS fan that was recommended by other users and I should be able to install w/o too much effort.

My biggest question that Undertow answered was the push or pull issue and he obviously said to pull the air out of the cabinet instead of pushing it back over the amp.

I could get really involved and install a thermostat so it only comes on when it gets too hot and then shuts off after cooling down, but for now I think I'll just go with the pre-amp switch and let it run when the system is under power regardless.
The best option is to get two fans, one pulls air in from the bottom, the second pushes air out through the top - or from side to side, across the equipment. If you are going to get the 110 fans I would consider the rheostat idea to slow them down (noise), or wire them in series which would cut their speed in half.
I like 24v DC fans, then usually run them at 12v.
Very quit Alternative.
Bmcleod or Russe41, would you run two 24v DC fans in series causing them to then run at 12v? or how would that work?

I will have three shelves in the cabinet with the amp on the bottom. What would be the best positioning for two fans? Originally I was thinking of one fan pulling air out of the back just behind the amp since that's the big heater. Not sure I could get circulation from top to bottom because of the shelves blocking air flow.

Possibly two fans pulling from the back- one high one low?
Jamesk58, a couple of observations. 1) If you're cooling a cabinet with tubes you do not need or necessarily want direct air directly over the tubes and 2) don't move any more air than you need to to keep the cabinet interior at room temp.

If your cabinet has openings on the bottom, and top(where your fan should be), you will be surprised about how little air you must, and can, move by one exhaust fan to maintain room temps in the cabinet, even if you should keep doors closed. Thats why I recommended 110v w/rheostat. Use a thermometer to measure air temp and adjust the speed up and down 'til you have it at room temp. Easy to do. Keep it simple as possible. :-)
Bmcleod offers very bad advice. Cooling fans should draw the air away from components, not blow air at them.

Good luck
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 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.
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.
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.
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.
Good planning Jamesk58. You're doing it correctly.

Have fun.
The amp needs to be on the bottom for low CG and overall stability. I also intend to get some heat tape to attach to the bottom of the immediate shelf above the amp. My Akai tape player is situated directly above. I don't believe I'll run into an issue with overheating the other componets, but do want to keep the amp at a reasonable temp.
So I just completed the install and the fan is just too freaking noisey! It hums along at something like 3100 rpms and you just can't stand it for more than 30 seconds. I powered it up prior by itself and it seemed fine but once installed in the cabinet you can hear it in the next room.

The electronics store person where I got some of the wiring and a little protectant grill talked me out of the reostat because he said it would be hit and miss to get the values right and may not adjust properly. But I can't leave it running full tilt all the time so I'm either going to toggle it for on/off sessions or find a reostat that works.

Geez, why isn't anything simple....
So the original link I posted was because the company specializes in low noise cooling solutions. But you still might salvage your installation with newbee's rheostat suggestion (or as I did in a another cabinet, 2 fans in series).

Another suggestion would be to make sure your mounting screw holes are slightly larger than the screws, and add rubber grommets under the screw head as well as a rubber washer between the fan and cabinet (cut out of old innertube). I've done all of this to reduce mechanical vibration into the cabinet which otherwise becomes a nice transducer. However, you'll still need to slow down the fans.
I used two 12 volt fans that were recommended on a previous agon thread. They are way quieter than the ones I bought from Radio Shack first. I mounted them on the "gel" isolator that you can buy from the fan supplier. Once I got them mounted to something solid they are very quiet. It really doesn't take much airflow to keep things cool and since I am pressurizing the cabinet I do filter the intake air. Here is the link
Good luck!
FWIW, I bought a fan rheostat for a fan at Home Depot and hardwired it to the fan on a long enuf cord so the control was easily assessable to use and it works fine. What is causing all of the noise it the vibrations and its very hard to eliminate these without reducing the RPM's substantially. You can reduce the effect of the residual vibrations by the way you attach the fan to the cabinet. What I did was to glue some heavy medium soft pad of rubber on to the cabinet surface and then glued the fan to the rubber. You can't just screw something on using rubber as a gasket. The vibrations will pass right thru the screws to the cabinet. Between the rubber isolation and the rheostat you should get the fan down to inaudible.
I'm far from an expert, but I experienced your same frustration a while back when trying to put a fan on my rack. After doing what you did, I found a very quiet 12v fan here. This is a 12v DC fan meaning it needs a 12v DC power converter like the ones you use to charge your cell phone or run a calculator. I had a few of these laying around, so I used 6v converter. On a DC fan, the speed is varied by adjusting the voltage, so mine is running at half speed (6v vs. 12v). I had some spare urethane dampers that Herbie Audio Labs uses on his tube dampeners, I used these to isolate the fan from my mount. I can't tell if its on or off unless I put my ear right next to it. Even at half speed (~900 RPM) it moves plenty of air. It may be an option for you. E-mail me for more specifics if you wish. Good luck.
Thanks Newbee. I will go for the rheostat to get the RPMs down and I like the rubber pad idea. Is that something also availible at HD?
Thanks to both the latest posters. Yes, I do need to get the fan speed down and will look for a rheostat today. 3200 rpms is just too much. As I mentioned above, the fan seemed pretty quiet when I powered it up loose on a table- even at full speed.

Will also get some rubber grommets. I did slightly over size the holes so there is some movement around the long screws. Will probably need longer ones now that I'll add 2 more grommets to each side of the attachment.

If it's still too noisy I'll look for a better fan. This one is off the shelf from RS but appears to be well built. It is a ball bearing style so we'll see if I can get the noise down.
So here's the latest if anybody is still following.

Got a 25 watt rheostat per local electonic store recommendation. Hooked it up wrong initially and then got it right. Installed it in the back of the cabinet. My cabinet is 36" high and is on casters so I can easily move it around on the carpet. Believe me this was smart considering how many times I've already had to move it back and forth to get my set-up right.

Everything is powered off the pre-amp via power strip w/surge protection. Pre is also fused. Just finished a 90 minute listening session at fairly good volume so the amp got to full temp. Fan was set at about 50% so I assume around 1500 rpm, maybe less. Fan sound was negligible with music playing and a bit less than the normal amp hum with ambient room sound( which is pretty quiet here).

So bottom line is the fan kept the amp and other electronics at a very reasonable temp running at about half speed. For good measure I set the fan at full speed for 5 minutes after my session and then shut everything down.

I know there are quieter fans availible but so far I'm happy with the set-up. Oh yeah, and I did install some rubber grommets on the attaching screws between the fan housing on the outside of the cabinet and the wood backing. Not sure how much this helped but it seemed like a good idea regardless.

Thanks again for everyone's input and comments. I hope this also helped someone else out with their own cooling issues.