Any one explain this?

[simon111]

Not a problem (for once everything is working) Just a query.

Having built the transistor switching relay driver over at Geofex, I have come across this anomaly.....

I use it to switch (true bypass) a distortion pedal remotely. I have made it so that when the relay is not powered it is bypassing the distortion pedal. They both run off a single PSU contained within the switching unit. But on a separate regulator (transformer has two secondaries , so completly isolated). One for the distortion, one for the switching (idea was so that it reduced any clicks that may occur)

The 0v of the distortion circuit is grounded to the chassis. But not the switching unit as I wanted to keep it separate.

Unless I connect the switching 0v to the distortions 0v it picks up interefence (mains hum from the PSU sound).

Why is this?

How can the switching circuit inject noise into a completely separate circuit?

It's not a problem as I just connected both 0v's together , (i.e Switching PSU to ground)

Just curios!

Simon111