Quiet 12V cooling fan for pro amp (24V supply)?

[Evenharmonics]

Any suggestions on using 12VDC computer cooling fan for pro amp? There are 24VDC cooling fans that are quieter than stock ones in pro amps but even quieter ones (< 20db) I've seen are all designed to operate with 12V. Can voltage divider be used to compensate the difference? I've read about people installing resistor (cause more heat?) to slow down the stock fans for lower noise but I'm looking to see how much further the noise can be brought down.
Thanks.

[Richard Ellis]

Use a 317 to drop the voltage...If you run a 12VDC fan at say 9VDC the 'noise' is considerably less...... to the point of dropping below your noise floor of your listening room. Put a pot on the 317 & drop it to an acceptable noise level (speed). Of course said fan will be less efficient..perhaps you can double up?

__________________________________________________ ______Rick.........

[Evenharmonics]

What about trim pot like this? It seems simpler to implement.

[nigelwright7557]

Originally Posted by Evenharmonics

Any suggestions on using 12VDC computer cooling fan for pro amp? There are 24VDC cooling fans that are quieter than stock ones in pro amps but even quieter ones (< 20db) I've seen are all designed to operate with 12V. Can voltage divider be used to compensate the difference? I've read about people installing resistor (cause more heat?) to slow down the stock fans for lower noise but I'm looking to see how much further the noise can be brought down.
Thanks.

You could try an adjustable via a pot dc-dc converter.

[AndrewT]

Have a read of the 2speed fan thread running now.

Careful with resistive Vdrop.
The motor might not start. This particularly becomes a problem as the lubricant thickens and the FAN and Bearings become dirty.

[Evenharmonics]

Thank you for the replies. The amp I am looking at has continuously variable fan speed with 24V supply. If I understand correctly, LM317 and other dividers put out constant voltage even if the input voltage varies which may no longer make it a continuously variable if I put 12V fan with such voltage divider. Would I be better off just using a resistor (around 270 Ohm, 1 watt) to drop voltage?

[AndrewT]

Hi,
the 317 output voltage can respond to temperature changes with just a few extra components.
The 317 can default to highest voltage at start up and then reduce to temperature referenced voltage. Again a few extra components.
No, I don't have a circuit.

[Evenharmonics]

Originally Posted by AndrewT

the 317 output voltage can respond to temperature changes with just a few extra components.
The 317 can default to highest voltage at start up and then reduce to temperature referenced voltage. Again a few extra components.

But this amp already has that controller except it puts out 24VDC max. I brought this up because of a concern about extra heat generated if resistor is used but now I'm wondering, will it be that much of heat to worry about?