Power supply buzz

[Brouilly]

Thanks ChrisA,

Ill experiment with a few different values. This may seem basic, but with a higher value grid leak resistor, will I expect more gain from the stage?

 

[DF96]

Grid leak resistors are typically in the range 100K to 1M. Too low a value adds loading to the previous stage, which may reduce gain there and increase distortion. Too high a value can cause bias problems if the valve suffers from grid current, so the data sheet will specify a maximum value for cathode or fixed bias. Sometimes you will see a very high value (4.7M or 10M) used with no other bias for a small-signal stage; this deliberately uses the grid current to provide bias.

Any currents circulating in the chassis may induce voltages elsewhere, but the value of the grid resistor will not affect this. Sound like an old wives' tale to me.

 

[Brouilly]

Pulling up the JJ datasheet for ECC83, its says under limiting values 2.2M for Rg.

So somewhere around there then?

 

[20to20]

Pulling up the JJ datasheet for ECC83, its says under limiting values 2.2M for Rg.

So somewhere around there then?

Charlie,

470K is a very commonly used value for the Rg. It's a middle of the road value. Diminishing returns for gain as you go higher... Too low values load the input device (low resistance to ground) and attenuate the sig.