Trying to blend (link) two channels tube preamp.

[motoskate]

Here's the deal: I have a Randall preamp module that I am trying to convert into an AC30. I would like to be able to link the Normal and Top Boost channels, as well as have the ability to blend them together. I have both channels wired to work independently, and they do as they should. When I try to link them together, I get noise and oscillation. I have 220k mixing resistors at the output and they both feed a 47n cap, before the output. I followed the AC30CC2 schemo mostly.

FWIW:
V1a--Normal channel wired directly to output control, bypassing following stages, CF and tone stack. Stage 1 of TB channel.
V2b--Stage 2 of TB channel.
V3a--Stage 3 of TB channel.
V3b--cathode follower

I used an extra stage for the TB channel in the interest of signal strength/volume.
I am using a dual stacked 500k pot for individual gain/volume control. I currently have the grounds from each pot jumped together, in case that may be a concern.

Any input would be greatly appreciated, albeit I'd love to figure this out on my own, but I'm stuck and need someone to suggest a door for me to open...LOL.

Would a summing opamp be any good here, or maybe a virtual ground to sum multiple inputs?

Thanks in advance!