New build for me. I am not an EE, just a DIY enthusiast. I will be using an Allied 6K7VG power transformer and only SS for power supply. I understand that B+ voltage will be a bit higher this way. Using EL34 as power tubes, will a 560 ohm cathode resistor still be OK or would it be better to increase the resistance of Rk? If yes, what value would you recommend?
Thanks for you help.
Thanks for you help.
It looks like the Allied 6K7VG is 375-0-375 (750VAC). With a solid state rectifier I would start with 680 Ohm resistors, maybe even 750 Ohms and calculate your power dissipation.
It's very easy to change those parts after the amp is up and running. And, it just seems safer to bias cold and go hotter, than to start out too hot (above 100%) and then work back down.
For comparison, my Edcor XPWR035 is 740V (370-0-370). I'm using a tube rectifier (which lowers B+ a bit), I have 680 bias resistors, and my EL34's are right near 100% plate dissipation. It looks like your EL34's might very well exceed their 25 Watt max using 560's.
David
It's very easy to change those parts after the amp is up and running. And, it just seems safer to bias cold and go hotter, than to start out too hot (above 100%) and then work back down.
For comparison, my Edcor XPWR035 is 740V (370-0-370). I'm using a tube rectifier (which lowers B+ a bit), I have 680 bias resistors, and my EL34's are right near 100% plate dissipation. It looks like your EL34's might very well exceed their 25 Watt max using 560's.
David
Many thanks dwinstonwood. I was suspecting that 560 ohms for Rk would not be the best place to start which is why I asked. I will follow your suggestion.