Blender without blend knob?

[Wounded Paw]

I want use a blender circuit to add a clean signal to an fx loop for bass, like the Paralooper
http://www.moosapotamus.net/THINGS/paraloop/paralooperSCH.gif

or B. Blender:


But I don't want to have a blend knob.  The clean signal should be at full strength and the volume is controlled by the output pot.  The fx volume is controlled by the volume pots on whatever pedal is hooked up to the loop.  I built a Paralooper this way and it does exactly what I want but there is a huge pop when turning the circuit on, doesn't happen when turning it off.  There is also a pop when switching on whatever pedal is in the fx loop, pedals which don't normally pop.  I'm assuming this has something to do with the caps before and after where the blend knob should be so I added some resistors (4K7 I think) in that place but it doesn't seem to help.  What now?
I've checked the input and output caps and they are in correctly and not leaking.  I also added an output pulldown resistor.

[Wounded Paw]

so here's the schematic of the paralooper as I'm using it now:



And the pedal that's plugged into the loop pops when turned off or on.  The paralooper pops when turned on only.