Tapped heater

[audiosalvage]

Will this work? Can I use both sides of the voltage divider or the same side?

[cdemike]

This wouldn't work if you consider the Thevenin equivalent of the circuit, specifically with regard to the bottom of the divider since the 3 heaters are in parallel with it. Just as an example, assuming that the 3 tubes in question are 12A_7s, they'd draw 0.15mA if wiring each tube's heaters in series as in the drawing. Applying Ohm's law, that would give R(heater)=21 ohms for each heater element since each would be rated at 12.6V. With 3 heaters in parallel, that is equivalent to one 7 ohm pathway in parallel to the 22k from the bottom leg of the voltage divider. From there, that would be equivalent to 6.998 ohms, making the voltage at the junction feeding the heaters 0.032% of B+. The math works out to have the same outcome if you wire the individual heater elements in parallel, so that wouldn't work either.

What are you trying to power from this supply? Correct me if I'm misinterpreting this, but it seems like you want a 2:1 voltage divider ratio with "B+" as-listed is 2x the heater supply voltage. If that's the goal, a 7 ohm resistor would work if it was used instead of the top 22k resistor and you only used the heaters as the bottom element of the divider. You'd need a resistor that's at least capable of handing 6W, though, and you'd be creating a lot of wasted energy by heating up that resistor.

[neskor]

maybe something like this:

[Stevem]

If you utilize the above circuit be sure to use fast recovery type diodes for the ac rectification .

[audiosalvage]

I'm trying to power a 12k5 amplifier where required B+ is 12.6v, same as heaters

[Stevem]

I need to ask what’s your reason for using a 12K5?

[audiosalvage]

Low voltage component availability. Have 12k5s laying around. Quiet practice amp