OK, I'm new to working out designs and tweaks to designs, so please be patient. I'm considering series use of OD3 and OA3 to provide 225V B+ for a 12B4 and/or 5687 linestage. I'm wondering if I can get away with a single stack of these (one of each) and still provide the 11mA (5687) or 29mA (12B4) PER channel current requirement for the triodes.
I know in theory I could simply calculate the ballast resistor for the regulators factoring in the full current requirement for the circuit, plus the current requirement for the VR tubes (15-20mA, depending on what works). I'm guessing I'll need different ballasts for the two circuits given their different bias currents, but assuming the trafo and rectifier/inductor PSU can handle the power requirements, can I use one OD3 and one OA3 in series and still provide two channels without a problem?
Is this a reasonable proposition? Am I missing something? Will the current variation of the two sides of the 12B4 or 5687 swing enough that I need to figure that into my calculations? And am I correct that if I simply account for 58mA for both sides of the 12B4 and 22mA for the 5687, and select the ballast resistors carefully I should be safe?
Thanks a ton,
Carl
I know in theory I could simply calculate the ballast resistor for the regulators factoring in the full current requirement for the circuit, plus the current requirement for the VR tubes (15-20mA, depending on what works). I'm guessing I'll need different ballasts for the two circuits given their different bias currents, but assuming the trafo and rectifier/inductor PSU can handle the power requirements, can I use one OD3 and one OA3 in series and still provide two channels without a problem?
Is this a reasonable proposition? Am I missing something? Will the current variation of the two sides of the 12B4 or 5687 swing enough that I need to figure that into my calculations? And am I correct that if I simply account for 58mA for both sides of the 12B4 and 22mA for the 5687, and select the ballast resistors carefully I should be safe?
Thanks a ton,
Carl