Mark,
Just connect them directly to the volume pot. I don't have my manual handy so I can't tell you exactly which wires go to which tabs on the pot, but you want to keep the signal plus going to the same tab on the pot as the common wire for the positive terminals for each channel that would have come from the switch, and of course on both left and right respectively. This is one of those places where a diagram would be helpful, but unfortunately I can't draw one for you.
-- Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)