Unfinished Gnat Fuzz Painted Effector Case Fuzz This is an effector case containing the Gnat Fuzz circuit. It can be used with a center-negative 9V power supply due to the charge pump that creates positive and negative voltage. It worked when I set up three NPN transistors, but it seems that the hfe needs to be selected. It had a wonderful sound with low hfe germanium transistors.