Tube Amps / Music Electronics
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|previous: moocow Hey R.G.,||View Thread|
|11/11/1998 10:13 PM|
|R.G.||Re: Choosing grid resistors|
I couldn't say it any better than Doc did.
If the grid leak resistor is too large, as the tube gets hotter, additional gas comes out and the grid leakage can nullify part of the bias voltage, which makes the tube run even hotter; you can have an output tube go into thermal runaway. For that reason, Doc's right on target that you should consider ALL the resistance between the grid pin and ground or bias voltage, and that the grid stopper should be as close to the grid lug on the socket as you can get it. If that means lowering the value of the leak resistor to keep things safe, so be it. There's usually plenty of gain other places to make up for the small amount you'll lose by lowering the common 220K leak resistor.
|Kevin Timm I try to do the layout so as to onl... -- 11/11/1998 10:57 PM|