9v electric mistress switch popping

[bagudan]

Hi
I have a pedalboard with 6 diy pedals. They all have pulldown resistors, so I get no switch popping, even though 5 of them are true bypass.
Recently I traded a pedal for a diy 9v electric mistress (from this project http://gaussmarkov.net/layouts/mwelecmiss/mwelecmiss-project.pdf) It´s a very nice flanger, and all the work seems very well done;)

The power supply is a Big John from cioks, regulated, but outputs are not isolated.

But when i put this pedal on my board, every single pedal on the board has a HUGE and annoying pop when i switch on and off. I´m guessing it´s because the flanger is not tru bypass because of volume-drop issues? I could turn it into TB, but I´ve heard of volumedrops, and that this is hard to solve.
Is there another way around this problem?

Thanks
Kasper

[bagudan]

Just tried measuring the voltage at the input and output. Theres 1,2 volts when measuring from ground to tip of output jack, and 1,0 volts at the input jack. is this a cap issue?
-Kasper