Does Your Tube Amp Run Hot??

[SWL]

Do any of you use a fan to cool your tube amp? If so, what type? Is it quiet enough?

Thanks,

-Scott

[sebrof]

Mine only has 5 tubes in it, so "hot" is relative. But tubes are hot, can't imagine why you'd need to cool the amp unless it's in an enclosure.

[Guest " "]

a few tube amps use fans (marshall, peavey, carver, etc) but's that's because they tipcally at rack mounted.

there are claims of geting longer tube life if you run your tubes cooler..using those accordian shaped tube collars, etc.

[mark1101]

My LK-72 does run hot, and I run it naked with no cabinet with plenty of space around it in the rack. Has been fine. Peach runs pretty darn warm borderlinehot in its cabinet, hotter with supertube, but never been an issue. C220 runs barely warm, no issue at all. No fans for me.

[Southern]

Scott,

Different type of tube amps run hotter then others (provided the output power is about the same). Class A tube amps tend to run hotter then class AB tube amps. My Dynaco is a class A so I just make sure there is nothing on top of it (especially a shelf) and use it as a room heater. My SS amp can run hot as well. Back in my college days my Pioneer's heat sinks would get so hot you couldn't touch them for any lengh of time, I never ran any fans on them just made sure it had pleanty of breathing room, after 30 years it is still working fine.

[tube fanatic]

Do any of you use a fan to cool your tube amp? If so, what type? Is it quiet enough?

Thanks,

-Scott

Tube amps are generally designed to operate at the expected high temperatures. However, if your amp is within an enclosure, it certainly can't hurt to put a small muffin fan on top of the vents to draw heat out. Some fans can be extremely quiet and won't interfere with your listening, even at low volume levels. Excessive heat is a definite cause of tube and electrolytic capacitor failure. The other factor to consider is the temperature of your listening room. For example, I don't use air conditioning, and my listening room is often in the 90's during the summer months. My amps run quite hot during those times. In the winter, when the room is in the mid sixties, the amps only get warm. Bottom line- if you're concerned about how hot your amp is running, use the muffin fan.

http://www.sofasco.com/acaxial.html

[SWL]

My LK-72 does run hot, and I run it naked with no cabinet with plenty of space around it in the rack

That's how I run my 222c as well......the amp I'm referring to. Mine actually only runs "hot" when I crank it. Otherwise, it runs warm-hot the majority of the time.

My actual concern......is that when I crank it the right output transformer's temp gets quite a bit hotter than the left side. Why is that? A comment from another forum was that the left output transformer has only two power tubes in front of it giving off heat. The right output transformer has two power tubes in front of it, the rectifier tube on the side of it and the power supply next to that resulting in more heat around the right output transformer vs. only 2 power tubes on the left one. Does this sound logical? It doesn't to me but I'm just trying to learn something here.

[mike stehr]

Scott,

Different type of tube amps run hotter then others (provided the output power is about the same). Class A tube amps tend to run hotter then class AB tube amps. My Dynaco is a class A so I just make sure there is nothing on top of it (especially a shelf) and use it as a room heater. My SS amp can run hot as well. Back in my college days my Pioneer's heat sinks would get so hot you couldn't touch them for any lengh of time, I never ran any fans on them just made sure it had pleanty of breathing room, after 30 years it is still working fine.

Are you sure your Dynaco ST-70 is a Class A amplifier? Did you strap the output tubes in triode, and buff up the power supply to make up the difference for strapping the output tubes in triode? As far as I know, a stock Dynaco ST-70 is a class AB amplifier. I'm guessing the reason a Dynaco ST-70 runs hot is the wimpy power supply transformer. The PS transformer is specced too small for the circuit, and it taxes the xformer a bit, so it ends up running hot.

As far as running a fan on a tube amplifier that is running too hot...wouldn't it be more prudent to figure out why the tube amplifier is running hot and fix it? I'm thinking that some folks starting into tube audio just can't accept the fact that tube amplifiers run hot.

Just how hot is too hot...what's the defining line here? When you smell paint bubbling and burning off? When you put your hand on a transformer and get third degree burns?

[Southern]

Are you sure your Dynaco ST-70 is a Class A amplifier? Did you strap the output tubes in triode, and buff up the power supply to make up the difference for strapping the output tubes in triode? As far as I know, a stock Dynaco ST-70 is a class AB amplifier.

My ST-70 is stock except for eliminating the selinum diode and replacing the quad filter cap, input and speaker jacks. I recall reading that the ST-70 is Class A up to 15 watts and Class AB from 15 watts to 35 watts. Since I bi-amp, my ST-70 doesn't get pushed that much.

[Cornman]

"Just how hot is too hot" as Mike said. I use the Transformers warmth & magnetic field to treat my arthretic joints.[] No fans hear, but I do give the Beast plenty of space to breath on a pedestal.

Cornman

[Groomlakearea51]

You have to be careful with fans.... The amp needs to be at it's design operating temperature. Example: AU-111 is around 145 degrees when measured on the rear top of the cover. I checked with a couple of techs on the tube amp, and the sugestion was to use a fan, very slow setting pulling air through chassis, but keep it near the caps and main transformer on that particular side. It was also suggested to let it warm up for 5 minutes or so at a very low volume before getting ambitious. My source for the fans is

drmckenzie1@sbcglobal.net

Hope that's of some assistance.

[H]

[tube fanatic]

Remember that power transformers are designed to run extremely hot without failure. This does not necessarily indicate that it's undersized for the job. Most are designed to allow an operating temperature of 105 deg. C (around 220 deg. F) minimum. If the transformer is delivering 400 volts at 200 ma (not unusual in a stereo amp), we're talking 80 watts of dissipation. Add to that 4 or 5 amps of filament draw at 6.3 volts, and now we have another approx. 24-30 watts. Now add the radiated heat from the tubes themselves and it's easy to see why the amp can seem so hot if you touch the transformer housings. So, as mentioned by others above, at the very least keep the amp on an open shelf if at all possible to allow maximum air circulation (and never put it on anything which can block uptake of air from the underside of the chassis where vents are typically located).

[NOSValves]

Are you sure your Dynaco ST-70 is a Class A amplifier? Did you strap the output tubes in triode, and buff up the power supply to make up the difference for strapping the output tubes in triode? As far as I know, a stock Dynaco ST-70 is a class AB amplifier.

My ST-70 is stock except for eliminating the selinum diode and replacing the quad filter cap, input and speaker jacks. I recall reading that the ST-70 is Class A up to 15 watts and Class AB from 15 watts to 35 watts. Since I bi-amp, my ST-70 doesn't get pushed that much.

Be careful believing what you read on the internet. The output tubes are bias hot but the ST70 is not class A by any means. The power supply has really poor regulation abilities. It may have 1 or 2 watts of class A operation before the voltages start fluctuating.

[fini]

I don't know if this is relevant, but in the olden days, when I was working in a camera shop, the conventional wisdom regarding slide projectors (which usually have fans installed), was to let them cool down (after use) with the fan off. Most important was to not move or jar the projector until it was back to room temp. Of course, not many of us "put away" our amps after a listening session...

[SWL]

I've taken some temperature readings. So far today.....after two hours of testing the hottest reading was 123 degrees Farenheit. That was after one hour of warm up time at 75db and a maximum output of 105db for 15 minutes at a time. (2 hours total)

I'm gonna monitor this for the next couple hours at different spl's but then gotta leave the house. I guess I'm somewhat surprised that the highest temp reading was only 123 degrees. Just going by sense of touch I thought it would have been slightly higher.

[SWL]

....in my spare time I go around touching objects that are 150 degrees. []

[tube fanatic]

I've taken some temperature readings. So far today.....after two hours of testing the hottest reading was 123 degrees Farenheit. That was after one hour of warm up time at 75db and a maximum output of 105db for 15 minutes at a time. (2 hours total)

I'm gonna monitor this for the next couple hours at different spl's but then gotta leave the house. I guess I'm somewhat surprised that the highest temp reading was only 123 degrees. Just going by sense of touch I thought it would have been slightly higher.

It should not be surprising to find that kind of temperature. If your hot water is typical, it is set at 120 deg. F; you certainly know what that feels like if you stick your hand under the tap!

[SWL]

After a total of 5 hours up and running.....the amp's highest temp reading was 142 degrees. It's not uncommon for me to have the amp on for 8-12+ straight hours on the weekend. I'll have to check it again when time allows.

As far as the right channel being warmer than the left......it was consistently 8-10 degrees warmer than the left channel. Is this anything to be concerned with?

[Southern]

After a total of 5 hours up and running.....the amp's highest temp reading was 142 degrees. It's not uncommon for me to have the amp on for 8-12+ straight hours on the weekend. I'll have to check it again when time allows.

As far as the right channel being warmer than the left......it was consistently 8-10 degrees warmer than the left channel. Is this anything to be concerned with?

I measured 160 deg. (using a IR thermometer) pointed at the output tube of my Dynaco.

I wouldn't worry about the right channel being warmer then the left since you have more heat sources on the right side. Keep in mind your tube amp doesn't have heat sinks like SS amps which tend to dissipate heat more evenly.