voltage current regulator
From several places on the net (including triodedick, DDDAC and diyaudio) I have read that tubes, even idht (the E series) ones, enjoy a voltage + current regulator. I would like to give it a try, but would also like to keep the circuit flexible (allowing output voltages from 5 to 55 or more volts to feed strings of P tubes).
I have an old Philips trafo with lots of taps on the secondary, so I can change the voltage going into the regulator. I would start with the needed V (out) + 10V (losses on the regulators). It's easy to check afterwards if the regulators aren't getting too much or too few volts to burn.
I prototyped the circuit and it did work. I just want to ask what you guys think of it: not the discussion of current regulated X votlage regulated X non regulated X AC, just if the 7805 is fine in this position. Also, I believe I can put more than 35VDC in this circuit!? The 7805 input is limited to 35VDC, but that's for the middle pin grounded. In this application it is floating.
Thanks for looking!
PS. This circuit would be a complete waste of energy for current hungry tubes: feeding one EL84 burns more energy in the regulator than the own valve does!