Not a module but works perfectly with modular, takes up no HP and no power! The Nervous Squirrel – Ring Modulator works great with line levels for soundcards/studio gear and also modular levels. It has a great gritty sound that adds a lot of character.

Some audio demos with 808s, 303s and some classic Dalek voice action at the website – http://www.nervoussquirrel.com/ringmodulators.html