• 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.

TIP50 + LM317 High Voltage Regulator


Paid Member
2001-10-12 3:47 am


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Try a MOSFET instead of a TIP50

These are variations on the tried-and-true Maida design, which I've used successfully many times in the past - all the way up to 1000V! The problem has always been that high-voltage bipolar transistors have low current gain, so you are forced in many cases to use a Darlington configuration. A buddy of mine just built a Maida variation using a 1000V MOSFET (in a TO-220 package) to stretch the voltage, instead of a Darlington pair. Works great he says. I don't have the part number but I can ask if anyone wants to know. There are surely a large number of high voltage MOSFET types available.

Check out the captioned SFM80 Schematic here:
Don't worry about his SRPP comment at the top of the schematic, not a SRPP in sight.
The whole front end circuit is available as a kit or PCB only from Curcio Audio Engineering (CAE). IIRC the PCB-1A. Of course, no circuit value on the schematic at CAEs website.
I've built a few of these - works well.


2009-03-09 2:30 pm
i think this is what he was looking for (see link)

i have it on file as i have been doing a rig tests on the (new to me) lm78s05cv from kec which has a 2A rating.

the heater sup looks good with a nice 6.3v @ 1.8mA using an old u709 as a test load.
the down-side with these is in the old days they would shut down on overload at only 500mA or so. and leave you with the amp running but with out heaters.

i hope this don't happen with an ecl82 and 9v light bulb per leg.


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