I’ve done a few layouts using this method, but thought it may be useful to include a little daughter board which will allow you to easily convert any existing positive ground effects to (daisy chainable) negative ground.
Just de-solder the supply and ground wire from the existing board, and solder to this board, then take a couple of new wires from the -9V output and ground connections on this back to the de-soldered pads on the effects board.
5 minute job and you can get rid of your positive ground power supply.
