45 tube grid leak resistor

[Rob7]

45 tube driven by 6SN7. .1 uF coupling capacitor. Does a 220K grid leak resistor seem reasonable? Should I go higher?

 

[euro21]

Most similar application uses 200...300k ... if the tube is the "classical" #45.
But ... these tubes are usually old, so grid current (near to 0V grid voltage) may vary, so higher value of grid leak resistor may cause a problem (operating point wandering).

 

[Rob7]

Thanks.