I would suggest replacing the resistor source load with a choke and reduce the voltage of the power supply . For the driver stage , you need a much higher HT rail and a much higher value load resistor . 6922 probably has far too much gain , look at some lower mu valves such as 12B4A or 6AH4 . I currently run a similar hybrid but I use RD16HHF1 RF MOSFETS which have low capacitance . Current driver is a type 26 which has mu of 8 , if your speakers are efficient like mine , this is all you need up front for enough system gain
Interesting little circuit, I would like to hear what it sounds like...
The supply needs to be well regulated otherwise it will hum like crazy.
6922 probably has far too much gain
Thanks for sharing photo - it gives me a great view of how complex/difficult something like this might be to undertake. I am totally ignorant when it comes to tubes/valves so can you give more details of ancilliary equipment/components needed to fire up that single tube? (small transformer and diode bridge/caps)
I like how simple it is - what kind of power can you expect to get out a SE class A like this with a single IRFN540 at 54v? I have a +/-53v PSU (SMPS Abletec) that might be a perfect candidate for powering this.
Besides lightbulb, a hotplate coffee cup warmer might be useful to keep your team warm.
Could 1 amp from a 7805 regulator suffice? Besides tube heater, are any HV's required for grid, etc? Also, is the output MOSFET part number critical (I havean IRFP240 on hand)?
Just need to order the tube... btw, just did a search - those 6922's ain't cheap! Is there a cheaper alternative?
No SS device will sound like a simple tube...... this is why tube are still used for very high end audio amps. Running up to 200V and a 6V filament is not too difficult if you scout around for a surplus amp, or mix 'n match..... eg two trafos mains to 8-24Vac secondaries and back to back will give you high voltage at low current; a couple of 12VAs will do it. 120Vac then rectified and smoothed gives you 170Vdc.
Thanks for tip on HV generation with the back to back small VA trafos. So for this particular tube, I need the 6v filament heater and the V1 voltage shown in the diagram in Post 1 requires either the two back to back trafos to get 200v or alternatively rectifying 120vac to get 170v DC is also required to get the tube to operate properly?