A Marshall AFD Sqealing problem (video included)

[M Fowler]

Based on Ceriatone's photos the shielding is going to pin 1 but why?

[martin manning]

Based on Ceriatone's photos the shielding is going to pin 1 but why?

This is a bit of local NFB, presumably to suppress RF oscillation. The layout specifies 2" of shield, so that's maybe 5pF from plate to grid.

[Lindz]

Maybe on that amp it is, but my Yeti is definitely pin 2. The shielding from the 1st gain pot to pin 7 does the same thing though the shield only connects at the tube.

the AFD layout on Ceriatone's website does show the shield to pin 1. I don't think Nik published a schem for the Yeti or Chupa.

[martin manning]

Lindz in your Yeti the first and second stage input coax shields are connected to ground, so it is not at all like the AFD. The only unusual feature in the Yeti is that the first stage's 1M grd leak resistor has been moved from the input jack to the tube socket, and it is grounded through the input coax's shield. Note that the shield on the second stage's input coax connects to ground at the tube socket, so it is not part of the ground reference for the grid like it is on the first stage.