The supplies really do need to be as close as possible, otherwise you will get an offset. I built up a small Mosfet circlotron a while back, I had issues with offset until I added regulators to my power supplies so that they matched.
I was thinking of regulating them but wasn't sure if it was viable for floating supplies.
I would need some careful planning for these as the power supplies draw some large amounts of current for several tubes in parallel.
Lets say min. 200mA per triode. 4 or 5 in parallel!!
Looking at a transformer that can supply 1 amp min, so some headroom, at least 1.5 amps, preferably 2 amps per secondary winding at 100-140 volts.
A regulator circuit that can handle 1.5 amps?? Any ideas?
I was quoted 120 USD for 1 tranny with 2 secondaries of 110 volts at 1.5+ (200 watts to be on the safe side) amps each. So a core that can supply over 400 watts.
I would go for a step down (220-110)(200 watts) as these are only about 37 USD each and easily available here but then I would need 4 big step downs on a chassis for 2 channels!!!!
(not including the B+ and heater transformers)
I will get some more quotes.
Originally Posted by Brit01 View Post
Could a cascode DN2540 be used as a sink to ground on the cathode?
Only if you want superb balance and overall performance with a simple, inexpensive circuit.
I could possibly implement a trimmer between the cathodes, with the wiper connected to the CCS to balance the 2 cathodes equally.
At present I have the CCS connected directly in between the 2 cathodes. Probably not the best most balanced design
Will try this.
The 9-10 volt difference in grid bias required to balance the output to zero DC offset seems to be caused by the FETs.
I swapped the source follower FETs and it followed the FET. Didn't expect that.
So I needed for example -49 and -58 volts on each rail to balance the output.
These only changed rails when i changed the FETs.
I will try another FET.
I swapped the source follower FETs and it followed the FET. Didn't expect that.
So I needed for example -49 and -58 volts on each rail to balance the output.
These only changed rails when i changed the FETs.
I will try another FET.
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