DOD 555 Performer Distortion

The orginal unit uses two 9V batteries and electronic swithing. I removed the latter, but left the supply voltage wanting the 18V. With this, i also left the (possibly) destructive polarity protection method in tact. For the supply, one can use two batteries or add a small daughter board to pump the standard 9V voltage close to desired 18V. That pump would be something like this or this.