Pedal popping sound power supply question

fretmeister

An electrical questions...

I have a couple of excellent pedals like Darkglass and Empress

When I use them with an isolated supply the switching is virtually silent and all is well. But when I use a One-Spot the pedal switch makes a popping noise. This happens even if the One Spot is only powering 1 pedal.

I understand that an isolated supply can help with hiss and hum etc between pedals but why would it affect the simple action of turning a pedal on and off?

It's no drama really as my proper boards have good power supplies on them, but I'd like to know why!