DHT for the poor that can´t afford an OPT

[revintage]

At present I have filament bias 2P29L using a 45H Transcendar OPTX primary as load , cap coupled to RD16HHF1 mosfet with those Triad chokes used for PSU smoothing and source loads .

Nice!
No problem from startup pulse when driver heats up? That´s what is worrying me most.

 

[316a]

Just turn everything on and off in order , or if you have the whole thing in one box , use a delay relay to turn on the mains for the mosfet supply transformer or use a slow start HT for the driver . Directly heated valves do tend to warm up quickly though

 

[Fuling]

A cheap TV damper diode in series with the high voltage rail should provide both delay and a slow ramp-up. Should be possible to find some P-series diode with a 300mA heater that matches the rail voltage for the output stage.

 

[revintage]

Might this solve the startup pulse problem?

 

[revintage]

I tend to overcomplicate things, this is how simple it should be.

A few bucks more with anode chokes from Aliexpress, still lower cost than an OPT.

Same harmonic pattern as a typical 6B4G/2A3 SE, but ten times lower figures.

 

[dht 4 me]

ROMY went down the smaller OPT for HF dedicated use rabbit hole years ago. You dont need that high inductance monster with the associated capacitive issues at higher frequency when doing a higher crossover use case. Not to diminish your project but there is no need for huge expensive OPT’s when LF is not needed.

 

[revintage]

Not to diminish your project but there is no need for huge expensive OPT’s when LF is not needed.

You are so right, because of that, I have dumped OPTs altogether.