12AY7/6072a Grid Resistor

[little eddy]

When looking at the 12ay7/6072a valves for my phono amp, I have kept looking for a datasheet that suggests a maximum grid resistor size.

The only one with a value is the GE one that suggests a typical value of 0M1, significantly smaller than other 9-pin valves that can be in excess of 2M0. http://tubedata.milbert.com/sheets/093/6/6072.pdf

Also I looked at the 6072-based AN M10 schematic I have attached. In the two instances where grid resistors are employed, they are only 50 and 100k respecively.

This would have to be considered as part of my RIAA calcualtions so:

Do I need a grid leak resistor?
If yes, is 100k max reasonable or might something much bigger be possible such as 1M0?

[Mike H]

1 Meg is a design maximum, otherwise it's whatever the circuit needs, just provided it doesn't go over the design max. Your circuit is OK as it is.

Apart from having no grid leak resistor at the input socket

47k ?