Ok, just imagine those two effects have their own enclosure. Two effects, two enclosures.
Normally you would bypass each effect with a single 3PDT. The connection between the two is a patchcable.
Now, we strip the two enclosures. replace the patchcable with 'normal' wires and connect output of dirt-effect to the 3dpt of the comp-effect.
But, here is the change:
-you connect the output of the compressor to the 2nd 3PDT, but the 2nd 3PDT leads back to the first 3PDT. The first 3DPT then goes to the ouput jackbus.
Maybe a little drawing would be easier. Hold on
