2. amps-preamps
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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?


128x128horseface
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.
unclejeff
1,313 posts
 
I also use strips of 1-inch granite to prop my tube amps a bit more above the shelf. Each strip is about 3-inches wide. Better air circulation.
veroman's avatar
veroman
299 posts
 
interesting thread! i made a layered posterboard and cork spaced 'breathing' elevating shelf for my dvd which i set atop my sony ht receiver to keep heat off dvd. cut out cork corner squares 2"X 2" and glued them to corrugated poster board (3 levels) cut to fit dvdp feet. stopped amp heat from reaching dvdp and still allowed amp to cool. i think the concern about the heat from lower amp heating amp above is valid. insulating the shelf from heat transfer is simple way to fix. you don't need much circulation for tubes heat imo but you do not want them heating other gear obviously. i like pc fan idea :)
warjarrett
105 posts
 
My father built a Dynaco Stereo 70 amplifier in the 1960's. He plugged a fan into the switched outlet of his home-made Dynaco preamp, and has had air blowing directly onto the power tubes for about 40 years. I'm telling you, he played a lot of records during those years, and plays a lot of CDs now, turning his system on almost every night. Well, those original Mullard EL-34 tubes (with Dynaco labels) are still working fine, test like new in my tube tester, and will not need to be replaced as long as he lives. Now a little more detail: he never used the amp cover, has his amp located under the cabinet that houses records and equipment, has the bottom shelf of the cabinet just about 1 inch above the top of the power tubes , and the cabinet has front and back decorative skirts that further enclose the amp in a very confined area. So I think his intention was to protect his wood cabinet from catching fire as much as it was to extend tube life. I think he accomplished both.
cajunpepe
255 posts
 
I believe the new ARC REF 110 has fans.
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