Re: checking bias on single-ended EL84 amp

5/29/2000 4:02 PM

Bruce

Re: checking bias on single-ended EL84 amp OK as Jason said, your actual plate voltage is the plate voltage minus the cathode voltage, or 269vbdc.   269vdc X .045ma = 12.1 watts.   Prett much perfect for a single ended EL84.   If you are worried about the current, you can increase the cathode resistance a little to get it down to 40ma or so.   I'd leave it just like it is and limit the screen current at idle to a couple ma or so.     Since the voltage drop across the 154ohm cathode resistor is only 7v, Ohm's Law, (I^2xR=P) or (ExI=P) would reveal that, at idle and no signal, the resistor is handling only about, .3watts...   .045a^2 x 154ohms = .312watts or   .045a x 7v = .315watts.   (your 7 volts was not dead accurate)   Nearly exactly the same answer two different ways though.   So, a one watt resistor would work fair and a two watt resistor would probably last forever at twice the .3watt power loading.     Bruce