If you're a Dead Head, you'll probably be interested in this one. It's the pre-amp from Jerry Garcia's Tiger guitar used from '79-'89 and built by Doug Irwin. It's a unity gain buffer to prevent signal loss with long cables. It can be built into a guitar like the original or into a 1590A. Other single op-amps can be used instead of the LF356N (TL071, NE5534, etc).