Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: John on January 11, 2012, 12:01:24 pm

Title: Heater supply question
Post by: John on January 11, 2012, 12:01:24 pm
What would be the effect of putting a 4700uf/6.3 volt capacitor in the heater supply? I've not seen this done, and know there must be a reason. I was thinking it would help with hum, (if hum is a problem) or does smoothing out ac ripple really not work the way I think it does?

Also, is it okay to insert a diode in the heater supply to drop the voltage a little?
Title: Re: Heater supply question
Post by: sluckey on January 11, 2012, 12:18:23 pm
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What would be the effect of putting a 4700uf/6.3 volt capacitor in the heater supply? I've not seen this done, and know there must be a reason. I was thinking it would help with hum, (if hum is a problem) or does smoothing out ac ripple really not work the way I think it does?
It would be kinda like putting a 1/2 ohm resistor across the filament winding. You'll draw about 11 amps. Probably not good for the cap or your PT. It won't do anything for hum.

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Also, is it okay to insert a diode in the heater supply to drop the voltage a little?
Only using one diode will drop the voltage a lot. Using back to back parallel (reverse polarity) diodes is a way to reduce filament voltage approximately .7V.
Title: Re: Heater supply question
Post by: John on January 11, 2012, 12:37:10 pm
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Probably not good for the cap or your PT.
No, probably not!

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Only using one diode will drop the voltage a lot. Using back to back parallel (reverse polarity) diodes is a way to reduce filament voltage approximately .7V.

Thanks!