I already built a Maida-style regulator for my tube phono preamplifier, but I didn’t develope a PCB for it. Now, searching in my hard drive, I found a design I did some time ago, that never saw the light. So I post it here in the hope that someone finds it useful!
You can modify the output voltage by tweaking R6: with the LM317, there’s a fixed 1.25V between the output pin and the adjust pin. I used 1kOhm resistor here between those pins, to obtain at least over 1mA in the divider chain: output voltage is
Vout = (1.25/R5) * (R5 + R6)
In reality in R6 flows also a little standby current for the LM317, about 50-100uA, so the output voltage will be a 5-10% higher. Use a 1W resistor for R6, it will get barely warm.
Note: make sure the regulator’s output gets proper loading, at least 5-10mA, or it could lose regulation.
Please note that both the metal tabs of the mosfet and the LM317 are at HV voltage. Do not touch them or let metal objects touch them: you should use mica or silicon insulator between the mosfet and the heatsink, or you can use a plastic package isolated mosfet.
C1 100nF 400V Q1 IRF840 or similar HV power mosfet R3 47ohm 1/2W
C2 1uF 400V IC1 LM317 R4 330ohm 1/4W
C3 470nF 400V IN screw connectors R5 1k 1/2W
D1 1N4007 OUT screw connectors R6 180k 1W (see text)
D2 1N4007 R1 100k 1/4W R7 4.7ohm 1/4W
D3 1N4742 12V Zener R2 100ohm 1/4W