Tube pedal with parallel tap. Voltage regulator or voltage divider

[gonzo]

I've made a simple tube overdrive with a single 12au7. Which has a 9 pin that can split the two heaters in pins 4&5 to run in parallel. So I can run the two heaters at 6 volts each to total the 12 volts the tube likes to see. In series I run it at 9 volts and it still sounds great, just less headroom. I've got an idea to switch between 9 volts and 6 volts. Some people have used a voltage regulator to achieve this. But it seems like this would add even more heat to the pedal

So my questions

1. Wouldn't a voltage divider work? And possibly cut down on the heat.

2. If I have to use a headsink in a regulator, would it be better to add vents near it or actually have more metal for it to radiate to?

3. At 9 volts the tube isn't very hot. At 12 I'm a bit worried building a wood sided metal top pedal. I'll add vents. Much like an amp head just more compact. Anyone tried a half wood enclosure with tubes? Any issues? Wood glue melting?

Thanks for any tips.

 

[Robert]

A passive voltage divider isn't the best solution.

If the resistor values are low enough to not limit current below the requirements of the filament they'll be smoking hot and dumping current to ground.

If they're high enough to not waste current the divider won't be able to deliver enough current to heat the filament.

You'd need a voltage divider as a voltage reference paired with some form of active device (emitter follower in the simplest form) to do the heavy lifting. You'd end up with a makeshift and inefficient discrete voltage regulator.

 

[gonzo]

Thanks. I might just buy a separate 12 v adapter and leave it as is. Seems like a hassle and a lot of wasted power.