When I come across a great product, I like to share... I just installed an Area 51 Tremolo unit in an amp I built for a customer. It is a self-contained bias wiggler tethered to the amp by an umbilical. It comes with excellent installation instructions and was a breeze to include in this gentleman's simplified AC-15 type circuit. The upshot is this is one of the best trem effects I have ever heard. My 2 favorites are the Marshall 18 Watt and Black Face Princeton. This circuit is equally as good. I highly recommend this unit to anyone who might be in the market for an add-on tremolo effect.