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I have a setup with a bunch of synthesizers and guitar pedals wired together with audio cables. I'm also powering the guitar pedals all with the same multi-plug 9V adapter. Since some of the pedals don't have dedicated power switches I bought some inline DC switches online that you stick between the adapter cable and the pedal so you can switch it on and off.

The weird phenomenon I'm experiencing is that switching one pedal on also switches on the others (whose switches are turned off) because the switch only cuts the power line and due to the audio cable connections there's actually an electrical circuit being formed across the ground connection of the audio cables and power line. Basically a pedal is linked to another via the ground wire, that other pedal is linked to a synthesizer via audio cable, another audio cable is linked from the synth to the first pedal, and now we have a ground circuit. It doesn't seem unsafe right now as far as I can tell, just inconvenient.

What I've realized is that if I had switches that cut both power and ground, they would work correctly in my scenario. My question is, would that be safe? I understand cutting the ground wire is supposed to be bad when power is live, but is this a big deal if both are cut and the voltage/amps are relatively low?

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    \$\begingroup\$ sounds like you may be on the wrong track about the cause of the problem ... please post a schematic diagram of a guitar pedal that is exhibiting the problem behavior \$\endgroup\$
    – jsotola
    Commented Apr 26, 2021 at 23:49
  • \$\begingroup\$ This might be easier to solve on EE.SE given that it depends on the internal circuits of your pedals (many pedals do weird stuff with their power circuits) and is all LV/audio (no mains electricity directly involved) \$\endgroup\$
    – ThreePhaseEel
    Commented Apr 26, 2021 at 23:56
  • \$\begingroup\$ I don't have the schematics handy but I've done extensive testing plugging and unplugging different cables and I'm pretty confident this is what's happening. My question is, can it be safe for a switch to break both the neutral and hot wire at the same time? \$\endgroup\$
    – Ben Wiley
    Commented Apr 27, 2021 at 1:08
  • \$\begingroup\$ Same things happen then you take plug out of receptacle. \$\endgroup\$
    – user263983
    Commented Apr 27, 2021 at 1:12
  • \$\begingroup\$ (1) Why not just switch the mains on-off to your 9 V PSU? (2) If you want to switch the DC then one switch on the 9 V+ is all you need. There is no need to switch the 0 V line. (3) As you have found, switching the 0 V line results in some pedals being powered by the audio ground. \$\endgroup\$
    – Transistor
    Commented Apr 27, 2021 at 6:50

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In Europe home laundry machines are usually connected to the mains through a wall switch that is called I-O switch.

See this

https://www.mlservice.it/content/images/thumbs/0074682_21509_5011N_320.jpeg

That switch disconnects both Live and Neutral.

That means that your idea is feasible.

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