• 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.

I need a negative supply rail--but how?


OK, I have a pile of 6N1P tubes kicking around here, and want to use them to make a bunch of op-amps for a project. All is good, based the design on the Philbick K2-W(J) with the values of all the passive elements re-sized accordingly, so it should be fine. Except...

The K2-W (and most any op-amp, I guess) needs a -300 VDC supply as well as the +300 VDC one (usual B+) one. Question is, how do a make a *negative* supply? A schematic would be most appreciated :)

Many thanks in advance!
Colt45 said:
300-0-300 trafo, full wave bridge. ground the CT.

You can use tubes.. say a 5U4 for the + rail, and a pair of dampers for the (-) rail. Or silicon.. whatever. Your choice

Dave Cigna kindly showed in an old thread of mine, that using a bridge and grounding the CT is (in fact) 2X FWCT rails wired in opposing polarities.

If symmetry between the 2 rails matters, all 4 diodes should be identical. 4X UF4007s, with each diode paralleled by a 10 nF./1500 WVDC ceramic snubber cap., will get the job done. A pair of 6BY5s, each having a separate, floating, heater supply is (IMO) the way to go, should vacuum rectification be a must.
Is this correct? Ignoring the sizes of everything, of course...



  • pos_neg_supply.jpg
    38.2 KB · Views: 165