4 replies to this topic

[AdrianD]

This is mostly for the people using rack amps, which usually have noisy fans for cooling. I usually listen to music at a low level so the noise was bothering me at times. After 3 years of putting up with the noise I searched for fan speed reduction and found a cool page :

Simple temperature regulated FAN speed controller

The schematic is simple, for the fan in the amp there is no need for rpm connection, that can be ditched.
I used an IRF 9630 transistor. The radiator is added because when the fan is off the transistor acts like a resistance and it heats up quickly.

Here are all the components on the board :



The back-side of the board :


The ntc resistor mounted with a metal bracket:



The board is outside the amp and wires are pulled through various holes in the back panel so I can alter the components in case I ever want to.

The speed of the fans for a given temperature can be set by adjusting the pot. I set it so that when the amp starts up the fan speed is at miniumum. If I ever get bored I'll set the pot so the fans start at over 40deg C*.

Overall, big difference in the noise level, definately recommended.

Credits go to the gentleman at www.webx.dk for coming up with the schematic.

[topgun]

Good work Adrian! Looks like a good thing to do on any fan cooled amp in the listening room.

[Aaron Clinton]

Build them and sell them.

[turdburst]

 Aaron, on 02 February 2010 - 12:47 PM, said:

Build them and sell them.

That wouldn't be a bad idea.

Phase 1: Collect Underpants
Phase 2:
Phase 3: Profit

It should work something like that if you don't mind the Southpark reference

[AdrianD]

I probably won't build it for the market, there are some problems :
Some amps run 24v fans and circuit needs different caps so there's no good solution
There's a risk of people setting it too low, a risk for the amps
Opening up a new amp voids the warranty.