• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

EF86 Triode Mode

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Hi All,

When running an EF86 in triode mode, is there any advantage to be gained by inserting, say, a 100e resistor between the Cathode & G3, or should one just strap the two pins together? Would a resistor affect the gain or any other characteristic of the valve?

The EF86 is the first stage of a Mullard 5-20. The HT & Cathode resistors have been changed accordingly to give about 1v DC on Cathode & correct Plate voltage.

-Eric
 
Family_Dog said:
Hi All,

When running an EF86 in triode mode, is there any advantage to be gained by inserting, say, a 100e resistor between the Cathode & G3, or should one just strap the two pins together? Would a resistor affect the gain or any other characteristic of the valve?



Hi there.....inserting a resistor on the g3 brings no performance advantge and will pick up noise.....so connect g3-->cath. It isn't in tube data sheet.
Make sure that pins 2 or 7 (or both) are connected to chassis.
see www.frank.pocnet.net/index.html

richj
 
Hi Rich,

Thanks for your reply. I have built four amplifiers with the Cathode & g3 shorted out, and one with a resistor betwee the two terminals. Although I couldn't hear any difference between the amplifiers, I was wondering which would be the correct way to go, and the reasons behind the fact.

I will remove the resistor from the one amplifier and short the pins out. With the input shorted and 'scope set at 10mV/div, I could detect absolutely no noise on any of the amplifiers on any of the amplifier's speaker outs.

The link you gave seems not to exist?

-Eric
 
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