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Howdy Folks, I'm keen on using a pair of SV83's. in parallel, that I have with a 125ESE at about 300V using the 2.5k tap.
Now my problem lies in absolute choices for the screen resistor and the cathode resistors as once I define a bias, say 2.5V at 31mA, I can't get the screen current at that grid voltage.
Theres very limited data available and the only stuff I have is the Svetlana datasheets and and at a stretch I can kinda maybe use the sheets for the Mazda EL83/6CK6 which seems an equivalent as is the 6P15P.
So if I use the EL83 sheets for anode current vertical and grid voltage horizontal and take a line down vertical from the screen voltage, where it meets at the quiescent anode current and the grid voltage, is the point where it meets the screen current lines the actual current on the screen?
That makes it 2.5V at 31mA + 4mA (for screens at 150V) which gives me a cathode resistor of 71 ohms ... which for two in parallel is 35 ohms and I've never seen a cathode resistor so low. Add to that the wattage required and it's only .9W? Am I missing something here thats staring me straight in the face. That all adds up to 300V at 31mA of 9.3 watts on the anode which means that with two tubes I'd be pulling 20W though an OT with 15W limits but only pulling 60 odd mA through it.
So the long and the short of it is, my questions in total, am I doing something silly or is it all kinda right and if I start with screen and cathode resistors a bit colder/ higher in value and work my way down, stopping at what sounds good of course, until I get something I like and the transformer doesn't get undully hot... or even warm... am I on the right track?
I've looked at many EL84 amps and they always seem to be somewhat lower in B+ and the voltages on the cathodes somewhat higher. Are they playing it safe or is it the that I'm going too clean and may want to set things up more like that for the sound I think I want?
I read something on AX84 that EL84's at 300 can be incredibly clean but at 250 they exhibit a really nice bite and crunchy thing that people prefer in Guitar amps.
I am so open to ideas and comments.
Now my problem lies in absolute choices for the screen resistor and the cathode resistors as once I define a bias, say 2.5V at 31mA, I can't get the screen current at that grid voltage.
Theres very limited data available and the only stuff I have is the Svetlana datasheets and and at a stretch I can kinda maybe use the sheets for the Mazda EL83/6CK6 which seems an equivalent as is the 6P15P.
So if I use the EL83 sheets for anode current vertical and grid voltage horizontal and take a line down vertical from the screen voltage, where it meets at the quiescent anode current and the grid voltage, is the point where it meets the screen current lines the actual current on the screen?
That makes it 2.5V at 31mA + 4mA (for screens at 150V) which gives me a cathode resistor of 71 ohms ... which for two in parallel is 35 ohms and I've never seen a cathode resistor so low. Add to that the wattage required and it's only .9W? Am I missing something here thats staring me straight in the face. That all adds up to 300V at 31mA of 9.3 watts on the anode which means that with two tubes I'd be pulling 20W though an OT with 15W limits but only pulling 60 odd mA through it.
So the long and the short of it is, my questions in total, am I doing something silly or is it all kinda right and if I start with screen and cathode resistors a bit colder/ higher in value and work my way down, stopping at what sounds good of course, until I get something I like and the transformer doesn't get undully hot... or even warm... am I on the right track?
I've looked at many EL84 amps and they always seem to be somewhat lower in B+ and the voltages on the cathodes somewhat higher. Are they playing it safe or is it the that I'm going too clean and may want to set things up more like that for the sound I think I want?
I read something on AX84 that EL84's at 300 can be incredibly clean but at 250 they exhibit a really nice bite and crunchy thing that people prefer in Guitar amps.
I am so open to ideas and comments.