There are times when you want to add true bypass switching to a pedal without re-housing and re-wiring the pedal. You can make a true bypass loop pedal cheaply and easily to accomplish this. Here are some wiring diagrams that you can use to make your own loops with various features.
For a more comprehensive article on these types of passive projects, see: True Bypass Loopers, Switchers, Muters, and Volume Controls
As simple as it gets, four jacks and one switch. This circuit accomplishes a true bypass loop with the minimum of parts. Plug the input signal into In, the output to Out, the In of the pedal you want to bypass to Send and the Out of the pedal you want to bypass to Return.
Add a few more parts to the previous design and you have a loop with an LED indicator.
What if you want to add a volume attenuator to your loop? For example, you have a pedal that provides an unwanted volume boost when engaged? You can add a simple passive volume control to the true-bypass loop to attenuate the signal in the return path. In this example, we wire a 100K audio taper pot as a simple voltage divider.