Powering down DIY guitar rig causes audio interface to stop working.

[DMME]

Hi everyone.

Whilst finishing my diy multieffects pedal http://www.diystompboxes.com/smfforum/index.php?topic=114333.msg1060997#msg1060997
I noticed a little something.

When i power down my guitar rig, usig the switch on my powerbarr, My USB audio interface stops working.
I'm using my interface to simulate a guitar cabinet in ableton since a real cab would be too loud where i live.
I'm thinking that my rig's power down is causing a current / voltage spike on the 230VAC mains.
Do you know of a way to limit / filter this spike without breaking the bank?
Please let me know

my guitar rig:
- 3 pedals powered by an isolated PSU.
- The multi effects pedal.
- Marshall JCM800 preamp clone.

Kind regards.

[J0K3RX]

Put a pedal in bypass mode that is running on a battery or power adapter that is not connected to your powerbar between the USB interface and the pedals you are powering off/on. See if it keeps it from causing your USB interface to stop.

[DMME]

Everything is fixed!

I have made a mains Ground connection in my room. (landlord wasn't too happy)
And the unit works perfectly now.
I now have 2 channel switches and beefed up the tube preamp.
Also I've added mode and select buttons to switch between band, stage, and "@#$%-all" mode.