Heat is the enemy of electronics. "Sounds" like you are on the right track.
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I have never do anything to cool my stuff any extra in summer. I like it warm, and use air conditioning to lower the temp only to 90 degrees. (Winter I keep the apt at 82 degrees) My old Forte' 4a ran in class "A", very hot, but after 18 years of just leaving it on mostly 24/7 i sold it.
I 'hear' all the stuff about "Oh you wear it out, or heat is the great ememy" well, in 45 years of owning stereo stuff i have NEVER had an issue with anything breaking, and i leave stuff on all the time...
So if you feel it makes you happy turning a fan on it, fine. No problem.
So there you have it, either cool it or don't, another definitive answer from Audiogon Forum. Out of respect for Elizabeth's generally insightful logic, empirical and apparently Florida tested, I realize how colloquial I might have been and so, have to ask why, "It seems each summer I need to do this."? Have you experienced a thermal shutdown?
Well the topic IS about heat AND not leaving things on 24/7 - BUT i did have CD player serviced not too long ago for a new laser, and the repair guy commented that the power supply was showing signs of getting old and some of the caps were starting to deform from overuse. He advise that I unplug when not in use. I guess a sharp repair person can tell these things.
I own ARC tube gear. Obviously, the component that runs the hottest is the power amp. The other gear, source and line stage, while also tube driven doesn't run anywhere as hot. I hear what Elizabeth is saying, but my sense of the matter is that heat "ain't" gonna help the gear last longer and can only hurt, especially the power amp. That sucker throws off a ton of BTUs.
There's a couple of ARC authorized techs out there. I'd be interested in their views since they fix the stuff.
I agree with Elizabeth, run it hot. If the manufacturer thought the equipment is running too hot they would have installed a fan. I believe stereo equipment sounds its best when it is running at its normal operating temperature. It is also important for the temperature to be equal for all transistors in the output stage so they can operate the same.
I grew up with central air and heat. The dealer that helped put my parents system in a half century ago, put muffin fans on the amp.
05-30-11: WilllandNoooooo! it does not draw 75A p-p all the time! The amp specs might say that it is capable of supplying 75A peak but the amp does not do that unless the load requires it. The 75A peak is just the max capability of the power supply transformer & capacitor bank to supply that much current.
it runs warmer to the touch 'cuz the bias is on high(er) side (to perhaps make it run longer in class-A before switching over to class-AB).
see if you can find out what at temperature the specific B&K model is supposed to run - if possible. Then make sure that you are operating it under those specified conditions.
For ex, many of Pass' designs (specifically the older Thresholds) were meant to have their heatsinks at 52-54C. That was supposed to be normal operating conditions.
05-30-11: HifihvnTrue Hifihvn that cap life is shortened very quickly by excessive heat BUT.............just because the heatsink is getting hot does *not* mean that the power supply caps are getting hot! Depends how the amp is made & where the power supply caps are w.r.t. the power transistors & heatsinks. The OP says that he's drawing heat out of the amp which presumably means heat from the power transistors only. The power supply caps could be very cool if the amp has grates on the top-plate, bottom-plate.
Cannot assume that power supply are automatically hot if the heatsink is hot.....
There are plenty of resistors close enough to the coupling, and other caps inside the amp to soak up the heat from those resistors. A lot of the time when I buy something, I look inside and see the caps or resistors leaning toward each other on one side of the amp (one channel), and not the other channel. This is quite common, and on upper end gear, not just mid-fi. I've seen this in all kinds of electronics, more so with PC boards. A lot of heat inside some of them. That's why I said it depends on the design. I have some stuff with a lot of clearance that needs nothing in the way of extra cooling. When some people buy this type of gear, they'll say it's just a big box of nothing. Maybe the designers did this for heat and other beneficial reasons.
No one seems to have mentioned the associated load on the amp and its output stage[s]. As a corollary, one sometimes sees ads that say "drove my Thiels/Apogees/'stats with aplomb". That's all good and well but it would seem that driving the amp to its upper limits might shorten its useful life and perhaps wear it out faster than one would with an easier load. Just wondering...
05-30-11: Tripperall (larger) power amps have output protection circuitry ( that kicks in if there is unusually high DC offset) + thermal shut-down circuitry that cuts off the output power stage if the heatsink temp goes too high (this is often monitored by transistors attached directly to the heatsink & the bias running thru these transistors is set to the upper limit of the heatsink temp that the designer thinks is safe) + the power transformer is also designed to provide lower current than the transistor's max so that the transistors always operate in their SOA. All these safety checks (idiot-proofing) ensure that (unless you short the speaker binding posts) the amp will operate safely & within its limits 99% of the time.
So, if the amp is driving somebody's Thiels/Apogees/'stats with aplomb then it is doing so within the SOA region of the output transistors (otherwise it'd be shutting down time & again & the owner would not make such a statement).
By "a matter of degree" I meant (along with a lame pun) the degree to which you're using the amp...running into a 4 ohm load to get 115db peaks for 5 hours might cause more heat than a day of light background music. I have a later MOSFET Forte' A/B that get toasty-ish only when I play something kinda loud for a while, but unless you have the amp in a VERY hot room I'd think excessive heat (risking shut down) is a design flaw, and the amp designer should have included fans. I'm amazed that some "all Class A" amps don't melt in "normal" use...but maybe I'm easily amazed.
When I received my Krell 300cx Steve at Krell said:
Don't leave it on 24/7
Yes it will run hotter than a lizards ass on a hot rock.
No don't worry about it as long as you have the required open air space as noted in the manual.
Now when I know it is getting hot I just smile and know she's just getting outa' 2nd gear.
Magfan, good catch!
My feeling re the original question:
-- Al :-)
This thread has been discussed many times. There are several ways to go here. First, basic engineering will tell you that unless it is absolutely necessary, you never leave this type of equipment on all the time. Components will defintely wear out much quicker with heat and time on. Manufactures will install fans only if it is cost effective for them to do so. Each piece of equipment is designed and constructed and sold at a particular price point in competition with other components at that same price point, much the same as computers and cars/trucks. A Mercedes SL600 is most definitely not the same as a Toyota. The same holds true for high end audio equipment. Also, unless the manufacturer is a goverment contractor for military usage, they will not perform failure test on equipment. Again, it is not cost effective. They won't test to determine the failure rate or how long leaving equipment on will take it to fail. It just won't happen. Some may adjust bias or add fans or elaborate heat sinking to dissapate the heat if necessary. Again, building to a price point and some of this may not be cost effective with the competition. If you want to leave your equipment on all the time, talk with the manufacturer and go for it. However, it is not necessary. Depending on your listening style. you can turn your equipment on an hour or so before hand and you would be good to go. But, to each their own.
If sound quality is important to you during playback, then try an experiment. Pick some music. Turn the equipment on two hours before hand and listen. take notes. Next day, turn it on one hour before hand and listen. Take notes. and then leave it on for an entire day, then come back and listen, take notes. Compare notes. I would be very interested to hear the discussion on the differences.
Also, it would be extremely unwise to leave tube equipment on all the time. Tubes have a very finite life span and you will wear out your tubes very quickly if they were left on. Very expensive endevour.
"Noooooo! it does not draw 75A p-p all the time! The amp specs might say that it is capable of supplying 75A peak but the amp does not do that unless the load requires it. The 75A peak is just the max capability of the power supply transformer & capacitor bank to supply that much current.
it runs warmer to the touch 'cuz the bias is on high(er) side (to perhaps make it run longer in class-A before switching over to class-AB)."
I am very aware of that fact but wanted to point out that because of the temperature difference of the (2) B&K amps I own. They both have very limited space above them in my rack so I felt a fan was only necessary for just the one amp that operated at a higher temperature. I don't know if it is better for the amp to use a fan to draw away excessive heat or not but I feel better about it due to the age of them(12+ years) and to protect my other components.