Modifying Stereo Echobase Switching

[Radamus]

Hello,

I asked this question over in the stereo echobase thread, but it's a different topic and it can probably use its own thread. Anyway, I want to modify the switching on the stereo echobase and I need some help. The link: http://www.diystompboxes.com/smfforum/index.php?topic=71201.0

Anyway, how it works right now, changing between long delays, rhythmic delays, and ping pong delays is only switched by plugging or unplugging jacks. I want to make that switching possible by footswitch, mainly to switch between rhythmic or ping pong and long delay.

I would use a DPDT to switch outputs A and B to either a switching jack DPDT or just have output B come out. The switching jack then switches whether A and B connect to a single output or individual outputs when the rhythmic/ping pong portion of the switch is selected, depending on whether there are two plugs in the jacks.

One plug: Footswitch determines whether both outputs are heard (rhythmic) or longer delay (output B) is heard.
Two plugs: Footswitch changes from Ping Pong to long delay in both speakers.

The trouble I'm having comes from mixing the sounds together. I know that I don't have to change anything for the ping pong delay, or long delay in one speaker, but I need to be able to mix the sounds without reducing signal quality, and I'm too much of a newbie to know how to do that myself. I know that some people use resistors from each output to the single point, but others use buffers. I'm not aware of the differences and am not skilled enough to design this myself. I have one extra op amp to work with if that will help anything.

Anything will help

Thanks
Conrad