Vintage Neumann/Gefell GNM14 - low-end loss?

Hi All,

A while back I acquired a very old, broken Neumann mic which I recently fixed. It sounds incredible!

Recently, the screen grid resistor on the RV12P2000 tube (right below the capsule) went out and the mic went dead. The resistor was marked 5M, so (lacking a 5M resistor) I replaced it with three large resistances in series to give me around 4.8M. I think we're back in business, but I can't help thinking the sound might have lost a little low end.

I am wondering if the original resistor on the screen was slightly different to begin with. Obvs, I can't measure it (the old resistor) since it is dead. Would increasing or decreasing the resistance alter the freq response all that much?

-Hildy

Found the answer to this question: The resistor in question, which connects the capsule and control grid (I erroneously called it a screen grid) to ground, was actually 50Meg, not 5. The printing on the original part was hard to read.

Thanks to Martin Schneider at the Neumann forum, I was guided in the right direction. With the capacitance of the capsule being 60pF, the 5M resistor formed a ~530Hz Hi-pass. With the 50M resistor, the hi-pass freq lowered by a factor of 10, and the original sound returned.