Can we talk about tube shunt regulators?

[kylej1050]

Actually, running the numbers over the datasheets the 6BQ5 doesn't do too bad as a lone regulator in this circuit. The circuit has -6V bias to maintain 30mA through the tube at 250v. If the 25mA load is removed the tube reaches equilibrium at 255v and -5V bias to pass 55mA. Not a perfect DC regulation but it keeps the output from shooting up to 350V if the load comes off.

 

[Sodacose]

You shouldn't encourage me, Kyle. 😉

I'm glad your eyeballing reached the same conclusion. Makes me feel a little more confident in my understanding!

 

[kylej1050]

Not sure if you've seen this yet but it is a shunt regulator that runs off a single pentode using it in pentode mode. Gets you more gain so you don't 'need' an error amplifier. Tube Based Voltage Regulators - Part 2STEVE BENCH site mirror by JACMUSIC

 

[Sodacose]

I think that's actually a series regulator with the VRs as error control. Voltage is dropped directly across the tube rather than the tube controlling voltage dropped across a load. Look where Bench takes the output.

He also has shunts on this page:

Tube Based Voltage Regulators - Part 5STEVE BENCH site mirror by JACMUSIC

edit: Woah, he has a 12AX7 cathode coupled amp on this page, too. How did I miss this?

 

[kylej1050]

You're right, I didn't notice the output was at the cathode...

 

[jackinnj]

Speaking of the DMOSFET CCS -- there are some issues with noise that I have been poking into. No free lunches.

 

[mashaffer]

Why wouldn't something like this (using the highest Gm tubes you have on hand) do the job? This 6N1P version seems to give about 85% reduction in sensitivity to load current.

 

[Sodacose]

The series resistor looks like it might be a bit of a heavy anode load for the tube, but otherwise I don't see why it wouldn't work.