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#1
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Fan Controller for Power Amp
I have a large monobloc amp I use for for subwoofing and I want to add a
simple but reliable temperature controller for the fan. For the main output heatsinks, is there a general temperature value that should not be exceeded, or is this highly specific to the output devices? Also, would a high quality fan controller designed for computer use be suitable? - Magnusfarce |
#2
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Most of the analog semi houses now manufacture fan control IC's -- you
can't simply use a thermal sensing device and an IC since the fan needs a threshold voltage to "get going" -- one of the simplest of these is to use an LM3524, modulating pulse width mode controller chip and a small fan -- the duty cycle is adjusted in relation to the temperature sensed -- the LM3524 has a built in error-amplifier and you control the V(error) with a sensor like an LM34. The temperature you don't want to exceed will be specified in the manufacturer's datasheet -- it is usually specified as the maximum junction temperature -- but it gets a little complex since it is virtually impossible to measure the junction temperature in real life. Instead, an approximation is made for the "case temperature", and the difference between this and ambient. put "fan control" into the search engine at www.analog.com and you will come up with a lot of neat implementations! "Magnusfarce" wrote in message ... I have a large monobloc amp I use for for subwoofing and I want to add a simple but reliable temperature controller for the fan. For the main output heatsinks, is there a general temperature value that should not be exceeded, or is this highly specific to the output devices? Also, would a high quality fan controller designed for computer use be suitable? - Magnusfarce |
#3
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"Magnusfarce" wrote in
: I have a large monobloc amp I use for for subwoofing and I want to add a simple but reliable temperature controller for the fan. For the main output heatsinks, is there a general temperature value that should not be exceeded, or is this highly specific to the output devices? Also, would a high quality fan controller designed for computer use be suitable? - Magnusfarce You could mount a microwave oven thermoswitch on the heatsink. These will handle a fair amount of current and are rated at 250volts so you can drive a fan directly. Cheap and reliable. I know of one amplifier manufacturer that uses a setup like this. r -- Nothing beats the bandwidth of a station wagon filled with DLT tapes. |
#4
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The simplest way, and the method a lot of pro power amps use, is a
bi-metallic switch bolted to the heatsink. This can switch mains or low voltage DC, it's just a mechanical switch. They come in a variety of flavours - 25, 40, 50, 60, 70 degrees C and higher. I've never found one of these switches that has failed. I wouldn't work on the maximum recommended temperature of the output devices, as running anything near that is likely to shorten their life and is just risky. Heat is the biggest enemy of a power amp. I'd choose a nice comfortable setting of 50 or 60 degrees C. Then the amp isn't cooking and will love you for ever. Incidentally, 60 degrees is pretty hot to the touch. Gareth. "Magnusfarce" wrote in message ... I have a large monobloc amp I use for for subwoofing and I want to add a simple but reliable temperature controller for the fan. For the main output heatsinks, is there a general temperature value that should not be exceeded, or is this highly specific to the output devices? Also, would a high quality fan controller designed for computer use be suitable? - Magnusfarce |
#5
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I would put a standard whisper fan that will easily fit, and let it run all
the time. A DC operated fan would be the best, to not radiate any hum or noise back to the amplifier circuits that may be near by to it. The above is what I do in my own equipment. I don't like to get over complicated with thermo control, and etc. The simpler this is the more reliable it would be. -- Jerry G. ====== "Magnusfarce" wrote in message ... I have a large monobloc amp I use for for subwoofing and I want to add a simple but reliable temperature controller for the fan. For the main output heatsinks, is there a general temperature value that should not be exceeded, or is this highly specific to the output devices? Also, would a high quality fan controller designed for computer use be suitable? - Magnusfarce |
#6
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In , on 11/24/04
at 06:37 AM, "Jerry G." said: I would put a standard whisper fan that will easily fit, and let it run all the time. A DC operated fan would be the best, to not radiate any hum or noise back to the amplifier circuits that may be near by to it. The above is what I do in my own equipment. I don't like to get over complicated with thermo control, and etc. The simpler this is the more reliable it would be. There is some advantage to keeping the noise down by monitoring the heatsink temperature, but, overall, I would agree with the keep it simple approach. One point to consider is the how the fan noise enters the room. Mount the fan such that noise conducted to the room is minimized. I've used fans that, when held in your hand, could barely be heard, but, when mounted to a cabinet anchored to the wall, could be clearly heard in the next room and down the hall. Don't be over aggressive with your airflow. High flows bring high noise. I've been more successful with DC, ball bearing, slow speed fans. If the amplifier, as designed, is able to safely dissipate its heat, but you are uncomfortable with the temperature, then a very small fan, always on, will work wonders. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#7
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"Barry Mann" wrote in message om... High flows bring high noise. I've been more successful with DC, ball bearing, slow speed fans. It's not the air volume so much as the air velocity that increases noise. If the amplifier, as designed, is able to safely dissipate its heat, but you are uncomfortable with the temperature, then a very small fan, always on, will work wonders. A small fan is not the quietest approach. A bigger fan running more slowly usually gives the same air flow with less noise. TonyP. |
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