Shielding the tube grid?

[craigslee]

Hi people,

I am in the process of installing a post overdrive tone stack to my amp and a very experienced tech I am getting advice from advised that I should shield the grids of specific 12AX7A tubes if I get oscillation.

Please explain how I do that, as his technical correspondence is a little more advanced than my level of expertise.

Thanks.

[Structo]

Need more details.
What is the amp?

My apologies. That's what I get for skimming.

[dave g]

He's not talking about tube shields, he's talking about using shielded coax on the grid wires.

Sometimes it can help tame oscillations, but not always. You basically want to replace the wires going to pins 2 and 7 on the preamp tube sockets with shielded cable. The center conductor replaces the wire that is currently in place, and then you connect the shield around it to ground. Make sure you only ground one end of the shield.

[craigslee]

Structo: Hot Rod Deville 410

daveg: Thanks so much for clearing that up!

This Forum rocks!

[Structo]

So on a HRD they don't use shielded cable from the jack to the first tube?

Since it is a pcb amp most likely the jacks are on the pcb as well as the tube sockets.

So how are you adding a tone stack to it and do you have any pictures you can post to help with your questions?