Cool Off Your Equipment: A cool tube is a happy & good sounding tube.

Niteshade · « **on:** 27 May 2009, 11:40 am »

Tube gear operates best coolly. I highly recommend using forced air cooling.

Tubes are expensive! Keeping them cool can more than double their life. I like the sound of cool tubes much better than hot tubes.

People will give you all kinds of advice and wacky things to try- but I assure you this is the BEST advice available to enhance your audio system. Not only is it solid advice, but it's inexpensive to implement!

JimJ · « **Reply #1 on:** 27 May 2009, 08:18 pm »

The trick is, the cooling needs to be silent enough not to intrude on listening. I know what you mean about forced air cooling, though, a lot of the tubed RF amps I've seen with 811As or twin 3-500Z RF decks use some pretty substantial blowers to keep things under control

Not really important to keep noise levels down for that use, though.

Tyson · « **Reply #2 on:** 27 May 2009, 08:21 pm »

If you have an open back av cabinet (but closed on front, top, bottom), what is the best method of directing the airflow? If I put the fan at the back, should I set it so that it's "pulling" air from the cabinet, or should I flip it around so it is "pushing" outside air into the cabinet?

Wayner · « **Reply #3 on:** 27 May 2009, 09:10 pm »

You can get muffin fans from Digikey for reasonable money. They are avalible in a variety of voltages from 12, 24, 48 DC and a 120 AC volt version. They move descent amount of air and are very quiet.

http://parts.digikey.com/1/parts-kws/muffin-fan

Here is another place:

http://www.drillspot.com/products/48983/Dayton_4WT48_Square_AC_Axial_Fan

You have to order the cordset seperately. It plugs into 2 terminals on the fan. We used these at work all the time.

Wayner

Niteshade · « **Reply #4 on:** 27 May 2009, 11:43 pm »

I once saw a muffin fan with serrated blade ends. Ever see that? It was supposed to be a VERY quiet design. I think I saw it on a 120mm fan in some catalog a long time ago.

Just watch the CFM and noise ratings. Lower CFM fans will be quieter, especially if they are 120mm instead of 80mm.

I'm using a little 10 inch box fan. It's easy to position and tall enough to 'see' over the transformers. It's not that noisy, but it's not super quiet.

Niteshade · « **Reply #5 on:** 10 Jun 2009, 10:46 pm »

Just a reminder about your power tubes: Keep them cool. If they seem to run hot, check your bias. If the amp feels like an oven then something is wrong. Sometimes closely grouped tubes will feel too warm- but they should never run extremely hot.

Aside from biasing, use some kind of forced air. Between good biasing techniques and forced air cooling, it will be easy to at least double the life of your tubes.

Cool tubes do sound better- what a great perk!

Kpt_Krunch · « **Reply #6 on:** 4 Jul 2009, 06:39 am »

I'm confused, tubes are supposed to run hot, that's how they work, it wouldn't work if it wasn't hot (at least that's my understanding). That being said, I keep my amp out in the open, with the tube cage removed. Lots of air flow around it and I wouldn't think of keeping it enclosed in a cabinet or anything. IMO - having some kind of fan or cooling system blowing on it is a waste (not to mention a distraction) unless you do have your tube amp in some kind of enclosure. But I don't necessarily agree with running your tubes 'cool' - though I understand your point about them getting too hot :

Niteshade · « **Reply #7 on:** 4 Jul 2009, 10:33 am »

Actually, tubes like to operate cooler than you would believe. Only the filament inside a tube wants to be hot, everything else wants to stay as cool as possible.

The objective of forced air cooling is to keep power tubes from gassing up so easily and to cool off the amp in its entirety. Electrolytics hate heat- they can dry up. Transformers dislike heat too. The amount of forced air is very little- about what a muffin fan are small desk fan produces. Not all fans are noisy, especially the low CFM ones. Even cool running amps will benefit. All you're doing is carrying excess heat away.

This is one of those small investments, tweaks that can save people allot of money. It works and works splendidly. BTW: Hot solid state amps will benefit greatly from this!

Big Red Machine · « **Reply #8 on:** 4 Jul 2009, 01:37 pm »

Quote from: Wayner on 27 May 2009, 09:10 pm

You can get muffin fans from Digikey for reasonable money. They are avalible in a variety of voltages from 12, 24, 48 DC and a 120 AC volt version. They move descent amount of air and are very quiet.

http://parts.digikey.com/1/parts-kws/muffin-fan

Here is another place:

http://www.drillspot.com/products/48983/Dayton_4WT48_Square_AC_Axial_Fan

You have to order the cordset seperately. It plugs into 2 terminals on the fan. We used these at work all the time.

Wayner

Thanks for the link Wayne, always looking for more DIY goodies.

One trick I use is to buy a 230v fan and run it at 120v. It doesn;t push as much air, but sure runs quiet.

Quiet Earth · « **Reply #9 on:** 4 Jul 2009, 02:53 pm »

One thing I don't like about fans is that they push dust into places that would normally be clean.

Quote from: Niteshade on 4 Jul 2009, 10:33 am

Electrolytics hate heat- they can dry up. Transformers dislike heat too.

That's why it's up to the designer to choose the proper size case and lay the parts out correctly. (There's nothing wrong with building it all in a bigger box.)

Niteshade · « **Reply #10 on:** 4 Jul 2009, 03:11 pm »

High velocity air does have a tendency to cram dust into undesirable places. I'm talking about low velocity air flow. Dust will not be an issue. It doesn't take much air to effectively move hot air away from a well ventilated amp.

Large enclosures do indeed help, but convection cooling is inefficient. I would rather have some air circulating around my prized audio gear. I don't like 'standing heat'. It's better to move heat away from electronics. Tubes that have cooler plates will last allot longer.

Be cool, man!

Quiet Earth · « **Reply #11 on:** 4 Jul 2009, 04:29 pm »

I understand your passion to be cool

. It's a good subject too. I've owned a few pieces of gear that had one or two parts inside that were screamin' hot. That always worried me.

I still think there are good practices of parts layout and convection cooling that have as much merrit as forced air cooling. This seems like an appropriate place to share it.

For example; each of my stereo components are built into a somewhat oversized chassis. This gives the designer enough room to lay out for both sound quiality and heat related reasons. Most of these components have vents on the bottom, top or both. In addition, the amps are single ended, which means that there's no need to crowd tubes into one tight location. (I suppose there's no need to do this with push pull amps either, but I always see them made that way.) I can put the front of my wrist on any exposed metal part of any chassis, including the power amps, and at most it feels luke warm. (A similar old school method of testing the baby's bottle milk before giving it to her). The use of after market feet helps with vibration management and gives the benefit of added cooling because of the bottom vents.

I suppose I could add a fan or two to reduce the heat even further . . . . . . . . . I should force the air on each tube to make a noticeable improvement, so I would need 6 fans just for the two power amps! (I don't think I'm clever enough to pull this trick off

)

JohnR · « **Reply #12 on:** 4 Jul 2009, 04:41 pm »

If the tubes have ventilation holes near them, then you could just force air through the chassis and out the holes - ? So, one fan per amp.

Niteshade · « **Reply #13 on:** 4 Jul 2009, 05:06 pm »

Cooling is extremely easy. One muffin fan or desk fan strategically placed will cool everything off. If you can place the fan a few inches away from the amp, the moving air will diffuse rapidly and encompass everything. Equal distribution would be nice, but even if it isn't, you're still evacuating hot air in the immediate vicinity. Depending on the amp I'm using, the fan is typically behind or behind-diagnolally the amp(s). One fan will certainly do it and it doesn't have to be fast and noisy. I'm using a 10" cheap box fan and usually have it set on low. I oiled the bearings in it for smoother, quieter operation.

BTW: Some large HF amps used a forced air cooling system and had a glass tube chimney around the power tube(s). The blower was mounted on the bottom-half of the chassis so it cools the insides and the tubes as well. Henry did a beautiful job with their amps when forced air was necessary. They used the chimneys with 3-500Z's.

Quiet Earth · « **Reply #14 on:** 4 Jul 2009, 05:34 pm »

Quote from: JohnR on 4 Jul 2009, 04:41 pm

If the tubes have ventilation holes near them, then you could just force air through the chassis and out the holes

They do, but they already run cool because of the design and lay out.

We kind of went from "cooling off each tube because they like to run cool", to just getting some air to circulate around the gear. If we're just talking about a little air circulation, then the ceiling fan seems good enough for that.

I honestly don't know how cold a tube "wants" to be when it's on, so I just assume that as long as the heat isn't allowed build and accumulate then it's running cool enough.

dmatt · « **Reply #15 on:** 4 Jul 2009, 06:25 pm »

Does the operating temp of the tubes change the bias?

The reason I ask is that my tube amp is in front of a window. With the window closed, ambient temp in the office is 70 degrees or so, I warmed up the amp and set the bias to 1.5 volts for each of the four power tubes. I opened the window to get more cool air in (it faces the 10 knot prevaling wind -- talk about forced air!). I remeasure the bias and it is now different by a 0.1 or 0.2 volts. I close the window, things settle down. Coincidence? Thought I would ask.

Thanks,

David

JohnR · « **Reply #16 on:** 5 Jul 2009, 12:33 am »

Quote from: Quiet Earth on 4 Jul 2009, 05:34 pm

Quote from: JohnR on 4 Jul 2009, 04:41 pm
If the tubes have ventilation holes near them, then you could just force air through the chassis and out the holes

They do, but they already run cool because of the design and lay out.

OK, I wasn't following why you suggested needing six fans

My mind then went off thinking that a strategically placed fan might be a good way to assist the convection cooling. I guess I'm thinking more from a DIY angle here.

Anyway, thought-provoking thread!

Kpt_Krunch · « **Reply #17 on:** 5 Jul 2009, 05:27 am »

So why do you need to run your amp for a while (30 minutes seems to be the general concensus) before the tubes get 'warmed up' and sound their best?

I follow your logic though and it makes sense, a 'cooler' tube will last longer, but I thought they were designed to run hot and the 'warmer' they got the better they sounded. So wouldn't cooling them, though lengthing their life, do the opposite to the sound (make them sound, well, worse would be the wrong word, lets say not maximizing their potential). That being said, since I just made a very large investments in some upgrade tubes for my main tube amp, I'm willing to try anything to have them last longer (3000 hours would be very nice

) and if buying a cheap muffin fan works, I'd go for it.

Niteshade · « **Reply #18 on:** 5 Jul 2009, 10:52 am »

I'm not talking about large volumes of air, so the tube's operating temperature would not be adversely effected enough to alter the sound. As was noted earlier, an amp was running in front of an open window that was allowing a considerable amount of air to blow on the amp. The bias voltage didn't change enough to be a concern. The glass envelope is a heat radiator. You don't want hot glass re-radiating heat back into the tube. That means it's not doing its job.

The air volume I'm talking about is minimal. It's just enough to wisk hot air away. It's just enough to feel if you put your hand in the general vicinity of the amp. My 10 inch desk fan is set on low and about 8 inches away from the amp, so the air column can expand and encompass the amp. Believe me, you can't touch the tubes even with the fan on! They still reach operating temperature and get hot. They're hot, but at least the glass is able to dissipate heat better.

Note: The ceiling fan was a great idea. That will help allot, more than likely it will be perfect.

All it takes is some moving air. You'll know it's right when it doesn't fell like there's a 'heat cloud' around your gear. It shouldn't feel toasty-warm near your equipment, nor too cold.

ecramer · « **Reply #19 on:** 5 Jul 2009, 01:49 pm »

Very interesting thread. I run a Rogue Magnum 99 Pre amp 4 6sn7's main and 2 12ax7's , 2 12au7's in the phono. Now i wont say you could fry an egg on the top but i will say that it gets pretty warm, as far as that goes the whole unit gets warm after a couple of hour. which always bothered me for two reasons , tube life and why its ok in the winter durng the summer i m fighting the air conditioner, (Still looking for that nice cheap SS Pre to run during the summer which i know one of you guys have in his closet and would like to unload )

I took a computer fan that i had laying around and hooked it up to a a 5 volt dc source which made it very quite. I tried a 9 volt but found it to be to noisy for my taste. I think it going to work like a charm the heat dont seem to build up like it used to still warm but no where near where it was. Not going to cure the second problem but i may just install a central vacum vent in the floor behind my rack and run some tube down to a bigger fan sucking the hot air out of the room. Nice twwek

ED