I'm playing with a linestage design and saw Glass Tube audio had a circuit for a 12AT7 which showed a 220K grid to ground resistor in parallel with the volume pot.
I have played with putting it in and I do get more dynamic but also more noise by the nature of having another resistor in there.
Its a simple circuit using a 5689 single half with output transformer. If the 50K pot is loading the grid why would the circuit need another resistor in parallel?
I usually don't see this.
I have played with putting it in and I do get more dynamic but also more noise by the nature of having another resistor in there.
Its a simple circuit using a 5689 single half with output transformer. If the 50K pot is loading the grid why would the circuit need another resistor in parallel?
I usually don't see this.
In almost all cases the resistor is there in case the control goes open on the ground end (or wiper) leaving the grid floating. That's a rare event but it can happen. If noise increases, perhaps try a better resistor.
I using a caddock which is about the quietest I know of. Would it be a fair assumption to say that with a 50K and a 210K grid to ground my effective load on the grid is 40K since they are essentially in parallel?
Depends on what that pot's purpose is. More commonly, the "safety" resistor will be much larger than the pot. Its noise is irrelevant since the pot is shunting it.
Everything in electronics is a compromise. It's called designer's choice. To get something, you usually have to give something. 😉
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