Implementing ampdoc's "Heater Scaling"

[LeftyStrat]

I was wondering if anyone has tried this? What did you use to scale the heaters?

I have a LM317 laying around, and thought about using it to scale the heater voltage.

My only problem is this would be scaling the heaters on 2xEL84, which should draw 1.52 amps. But the LM317 is current limited to 1.5 amps.

If not using a regulator, are you guys just using a mosfet like the VVR?

[roberto]

You can simply use transistors in parallel.
Take a look HERE.

[andrew]

Hi Lefty, I asked Ampdoc1 about it and it was meant to be used on the output tubes only. I used a rheostat on a PP kt66 build and it worked but I didn't like the effect. Also you have to heat the tubes up at normal voltage then back it down to where you want it.

[LeftyStrat]

Hi Lefty, I asked Ampdoc1 about it and it was meant to be used on the output tubes only. I used a rheostat on a PP kt66 build and it worked but I didn't like the effect. Also you have to heat the tubes up at normal voltage then back it down to where you want it.

What didn't you like about it?

[Structo]

Yeah if you are going to go that route you might as well use DC heaters.

My Carvin Belair has DC heaters on the preamp tubes.
The EL84's get AC heaters.

Real simple design.

[andrew]

Lefty, I wanted to use it for more of a variac smooth distortion effect but it didn't sound right to me. Maybe it was the preamp I was using at the time.It does work for attenuating the volume though.

[dorrisant]

Ok... how would you limit the voltage range (upper and lower) of the circuit posted by Roberto above? ...And thanks for posting it, Roberto.

Tony