• 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.

proposed 833 design

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Needing something to pull me out of the 'depressed' state that work has left me in over the past year - it had got so bad that I have now resigned and am just working out my notice period, a whole six months:xeye: but a least that is an end to it then. Anyway needing something to lift my spirits and being inspired by the 833 pictures of Reinouts amp, I have bought some 833s (from Halfin - they were great to deal with).

Now I just need a design... well I have knocked one up using PL802 in pp as a driver (see diagram). but I am not sure what operating point for the 8333 to use. I like the look of Va=750V, Ia=350mA and Vg=+25V. It looks like I can get a very linear swing for +/- 25Volts input with maximum input of +/-50volts before clipping the output. This with a 3K OPT. However I am wondering what op points other people have used or would suggest???

I will make the high voltage supply bipolar to half the B+ to earth risk at the cost of doubling the number of caps and chokes in the power supply - a worthwhile trade off for me. I have most of the components for a +/- 400V to +/- 800V supply at 400mA so that will do one channel! Just one to go...

I am lucky that I have two surplus switch-mode psu of 12V at 10A that I can use for filament supplies. I'll feed the psu through CLCLC rf filters to reduce the switching noise even further and connect that to the filaments.

Any suggestions or thoughts are most welcome

ciao

James
 

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