This is a loud, obnoxious, horribly noisy piece of hardware that should not be used by anyone, anywhere, ever.

I took one of Oliver Ackermann of Death By Audio's purple business card PCBs and modified the circuit contained on it. The original uses a gained-out LM567 tone decoder to make really terrible noises.

I added:

1) a master volume - it really needed it

2) a range toggle for the speed of the ring modulations: Hi (squee) and Lo (choppah)

3) an input for a 2 volt condenser mic so you can use this as a vocal effect. As well as a switch that toggles between instrument and mic inputs - THIS IS AN ACTIVE 2 VOLT INPUT - don't use passive or contact microphones. I'm including a mic built specifically for this purpose with the sale.

4) an expression jack that allows you to control the big yellow "Frequency" knob with a standard TRS M-Audio or Nektar-style expression pedal.

I also wired the stomp switch to disconnect power to the LM567 when this effect is in bypass because it is so loud that noise bleed was a problem.

The video I am linking to shows the basic circuit but does not contain any of my modifications.