Going to repost this so its not lost on the bottom of the page

I'm just finishing off the schematic and then I'm going to tidy it up. I've got 2 isolated outputs for the 3 amp setup that route the signal back to the main output if a Jack isnt present to avoid ground hum. Not sure if I need to add opamps to mix the signal back into the main output if there isnt a connection?
Also, I think I'll add 3 external level pots. Should help get the mixing if required. (Also I've put the opamp as a LM324 but thats to be decided - I just put a quad on just in case I needed some to mix signals).
Also I've made a mistake with the switched Jacks and connected the switched signal to ground - sorry/