• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

power supply suggestions and advice

Hi guys - I need to derive a +50/-50v supply for the source followers on my 1625 pp amp (vapourware but getting there). Bias on g1 of the 1625s is -22.5v and I'm aiming to run around 10ma through the FETs. Not a lot of current needed obviously, but rock solid V would be good.

Power supply is shown in the attachment - the 6.3v windings are already spoken for as all the tubes I'm using have 12v heaters. The 5v supply is good for up to 3A at least, and the B+ winding has a bit of capacity left.

That leaves me with the following options:
  1. fit a separate 30-0-30 ptx
  2. voltage multiplier on the 5v winding
  3. create suitable rails on the main winding

#1 has space issues and is just, well untidy! I'd like to avoid it if possible but...
#2 is possible, but is it going to deliver enough voltage without noise and impedance issues?
#3 I have a gut feeling is begging for hum and stuff from mismatched impedance between the + and the - rails.



  • 1625 power supply.JPG
    1625 power supply.JPG
    61.7 KB · Views: 100
  • 1625 v1.01.JPG
    1625 v1.01.JPG
    50.9 KB · Views: 95
Last edited:


Paid Member
2005-03-11 11:09 am
Munich, Germany
hi, my preference would be #3 (if space is small) or #1 (if space is no problem). voltage multipliers can create noise due to the many diodes switching in there, and the efficiency is not that good. the noise can be filtered easily - in fact, the gate node of the mosfets are so high-ohmic that a smallish RC filter should do the job.

how do you intend to change the -22.5V to adjust the bias?