Marshall 18W 1974X MV mod problems

[rf7]

I'm putting in a post PI master with a dual 1M pot and 2 .1uf caps feeding the grid resistors to the EL84's and I'm getting popping at the top of the MV pot. Shouldn't the coupling caps on the wiper and the top of the pop keep DC off of the pot? I'm taking the output of the PI off of the two .01uf caps and tying them to the top of the pots. And now I'm getting popping from the bottom of the original volume pots too. I tried different caps for the .01uf's and got the same result.

Here's a link to the schematic:
http://www.drtube.com/schematics/marshall/18wr.gif

[loudthud]

Where are the 470K resistors connected? They should be on the EL84 side of the pot. The additional caps arent really needed because of the cathode bias but leave the 470K's in as a safety measure.

[rf7]

I initially tried it without the 2nd cap, but I had pulled the 470k resistors. I'll re-try it that way.

[Jag]

Speaking of which, is there any trick to making the taper a little smoother on this type of MV?

Most of the action happens at the bottom end of the rotation.