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Tubes and forced air cooling ...

Hello,

Time for another tube question. First of all, thanks to the folks who post good information on this site. I know the sharing of information freely can be a pain but it's the backbone of Audiogon in my opinion. You all help to keep my tube equipment in good health and that makes me happy.

Ok, down to business. I am running the following setup in a home made rack.

ARC VT-60 and a Mark Levinson ML 27.5 on the bottom shelf the amps have about 6" of vertical clearance to breathe before the next shelf.

The next shelf has a Levinson 360S DAC and a No 37 Transport side by side and they have about 2 inches of vertical clearance to breathe.

The next shelf holds my Modwright SWL 9.0 Linestage and my Dynalab Tuner side by side they have about 3" of vertical clearance.

The amps get hot ... especially when I add ale on a Friday night. Too hot? I'm not sure ... but hot enough for me to put a small desk fan behind them to keep the air flowing. The fan works well but my question is :

How does this affect the amplifier? Tube amplifiers are designed to get hot ... that's the idea ... right? At what point do I risk negative impact on sound quality? Do I even want to go down this road? I see that ARC has put fans in the VT-100 so I don’t think I'm too far off base. I don’t like the fan noise so I am having fan mounts built and I am going to use 12 volt 120mm ultra silent PC fans. A little less air flow but very, very quiet. They will be easily replaceable and will only cost about $7-12. I figure I will get a couple years out of a set. I'll run one across the pre and one across the amps.

What do you think?


horseface
viridian's avatar
viridian
4,184 posts
 
I think that the "fans are bad" lore has no basis in fact, as Audio Research actually made a product called the Fan Base which was a base with built in fan. Here is a link to the picture of one:
http://www.arcdb.ws/FB/FB.html
tobias
1,534 posts
 
My Shanling tube monos are on the bottom shelf of my 5-shelf rack. Their ceiling is the next shelf up, about 2 inches from the tops of the output tubes. That was too close for me so I removed the second shelf. The amps now have 10 inches of clearance overhead and they stay a lot cooler. It's a pain to lose the shelf, though.
horseface's avatar
horseface OP
222 posts
 
Thanks all,

To clarify the Levinson and ARC are also side by side with 2-3 inches on both sides and I only run one at a time. I did run them both for a while in a bi-amp arrangement ... I was very pleased but not to the point of running that setup permanently. I like to run the Levinson in the summer as the ARC heats up the whole room. As for the VT-60; I have the cover on the amp so the air blowing across the unit pulls heat transferred to the chassis cover not the tubes directly... in that regard, I guess the cover acts as a heat buffer. The DAC was getting warm which was how this all got started. When the 360S gets too warm it gets very grumpy. I checked it with the desk fan on and it's just a bit warmer than normal. It's all running fine now. I have just completed a test with and without the fan. I cant hear much if any difference in sound. The fan project is a go. I am going to avoid the fan directly blowing across the tubes and I am considering pulling air vs pushing.

I'm stuck in this little 14' X 15' bedroom until I build the addition to my home. I am really intersted in a pair of Cary or McIntosh tube amps but in this room I think I might cook myself. I want to pull the amps out and set them up close to the speakers on amp stands with lots of room to breathe. Until then ... the VT-60 is as far as I want to push it.

Thank you
elevick
2,439 posts
 
With a pair of Cary amps, you won't need heat!

Honestly, the easiest solution is to pull your amp out of the rack. Find it a better home or on an amp stand. Pre-amp and gain tubes produce very little heat by themselves. The amps will cook everything above it.

I would never use a fan. 1-it would have to be plugged into a seperate circuit to avoid noise. 2-you very easily can get added noise by the "breeze" blowing over the tubes. 3-even if the fan draws air away, you will end up with filthy equipment.

Buy some Pearl tube coolers if you really need.
inpepinnovations1e75
395 posts
 
When you are 'drawing' the heat away from the tubes using induced draft, what air do you think that the tubes air are getting to remove the heat? The same cold air as if you had the air 'blowing' directly on the tubes as in forced draft. It doesn't matter how the air is circulated over the tubes, induced or direct.
With sufficient overhead space AND surrounding space, natural convection is sufficient, i.e. don't put power amps in cabinets or in tight shelves without fan-cooling or leave them out in the open.
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