5F2A with a 6L6 prebuild questions

[Gerard]

Maybe I misinterpited the power transformer (or the math). It is an old stancor 360-0-360 at 90ma. 6v at 3a and 5v at 2a. So I figured 360v x 1.1(5y3) = 396 volts and 360v x 1.3 (gz34) = 460volts, am I missing something? I am still kind of new to this. Thanks for the quick answers to my questions.If I have the wrong P.T. what kind of voltages to I need to have?

[MWJB]

"I will be running the 6l6 at about 400 volts with a 5y3 and about 450 volts with a gz34 recto" those figures don't scan...what PT are you using what is the B+ secondary rating for VAC & mA? A single ended 6L6 amp will only draw 60-75mA at idle, not enough current draw to to create the voltage drop that you are anticpating, a handful of volts difference is more typical.

At over 410vdc to ground from the 6L6 plate (pin 3) a 680ohm cathode resistor (or 800ohm depending on voltage) will be good. At 410v and less, 470ohms will be spot on. Bias to the highest voltage with the GZ34 and the amp will still work fine with 5Y3. DO NOT use 270ohms unless you are thinking of running the B+ at well over 100v less than what you are currently anticipating. 10W resistor rating, bypass cap should be rated for 100vdc.

100uf for the main B+ filter, 40uf for the screen supply, 10uf for preamp supply.

Plate current for the 6L6 should be 55 to 65mA-ish so an OT rated at 70mA (125DSE?) will suffice. Try the 5K tap (will also work fine for 6V6 if voltages allow), then try the 2.5K tap (6L6 only) and use the one you like the sound of best.

[Gerard]

Hi, I have just about all the parts on hand to build a 5f2a with a 6l6. I have some questions about the bias resistor and O.T. I will be running the 6l6 at about 400 volts with a 5y3 and about 450 volts with a gz34 recto. The P.T will handle the load of the tubes, so thats not an issue. What O.T would be a good choice? I had my eye on a Hammond 125ese 15 watt with 5k primary.Also should the bias resistor be a 5watt or 10watt at around 270R or so depending on the voltage? and should I raise the value of the filter caps , if so, what to values?


Thanks again for your time. This is my third build, my first one was a Mission 5e3 that I kept stock and love the sound. This forum has been a great help to me over the past years and I appreciate all the help.