Cooling fan : AC or DC supply ?

[archaos]

Hi guys, all is in the title. Yet I wish to install the fan with an independent power supply ; Merlin's power supply book says that DC fan too close from the preamp can induce noise.

Thanks for your inputs, ideas, suggestions. 

               

[LooseChange]

You don't need a fan on the preamp tubes so DC will be fine.
I made a simple DC power supply coming off the 6.3v heater supply. I ran a 12vdc fan. Since it ran at around 8vdc it ran a bit slower and was very quiet.

[archaos]

Thank you.

[tubeswell]

DC is quieter/less hum-prone

[jojokeo]

Can it be as simple to just throw in two 1n4007 diodes off the heater wires and hook the fan right up to that? But then what if the heater's are raised to a higher AC voltage...? I'm guessing it wouldn't matter or would it since it's only a ground "reference" so it would still only see the 6.3DCv like the heaters?

[tubeswell]

Can it be as simple to just throw in two 1n4007 diodes off the heater wires and hook the fan right up to that? But then what if the heater's are raised to a higher AC voltage...? I'm guessing it wouldn't matter or would it since it's only a ground "reference" so it would still only see the 6.3DCv like the heaters?

I think it you did that you would get the effect of humps from the rectified pulses going back into the ground return path

[phsyconoodler]

Old Traynor amps used AC fans that were slowed down with a big resistor.They weren't noisy,but the olf fans often fell apart after a few years,just like old fans of the day.They weren't built particularly well.A small modern 115v fan would be fine I should think.

[LooseChange]

Can it be as simple to just throw in two 1n4007 diodes off the heater wires and hook the fan right up to that? But then what if the heater's are raised to a higher AC voltage...? I'm guessing it wouldn't matter or would it since it's only a ground "reference" so it would still only see the 6.3DCv like the heaters?

Need to add a filter cap. Like 1000uf @ 16v (just a guess)

[jojokeo]

Is there a recommended schematic or anything for a simple 4" computer fan? I have a couple laying around if I want to go this route.

[phsyconoodler]

Weber has a schematic on his site for hooking up a fan.

[jjasilli]

Here's how I did it.

[jojokeo]

Thanks for the schem. - I have < 40vdc applied to the heater artificial CT - do you think this will affect anything or cause something else to be needed?

[archaos]

Here's how I did it.

Which software allows to read your schematic ?

[jojokeo]

Go here and D/L the Jschem program for your operating system

http://www.el34world.com/Forum/index.php?topic=763.0

[kagliostro]

A simply two speed schematic

http://taweber.powweb.com/store/fan_schem.jpg

http://taweber.powweb.com/store/modkits.htm#fan

Kagliostro

[archaos]

Thanks a lot guys !