I ordered this Hurley two-channel preamp about a month ago, but I've since purchased a two-channel bass head and don't need it. It has never been gigged. This preamp runs on a nine-volt battery. It is the same as the one for sale on the Hurley site except that mine has a stereo input-jack. The tip is set to Bridge pickup/channel and the ring is set to the Slap pickup/channel. The two channels though can be used to blend any two sources. Here is a link to the site: Hurley website These are $75 plus shipping new. I will sell mine for $60 Paypal shipped. From the Hurley site: 2-Channel Preamp $75 The Hurley 2-Channel Preamp is the ultimate preamp designed for upright slap bass players. It has two inputs connected to two circuits to get that perfect mix of bass and slap every upright bass player dreams about. The bass and slap inputs have their own separate volume and tone controls that are mixed to a single output. The volume portions are a 20x gain boost and the tone controls allow you to dial in that perfect sound. Like the single channel preamp, this unit is small enough to mount directly to your bass. This unit requires a 9v battery (not included). There is a toggle switch to turn the preamp on and off with a LED indicator light. The switch is a battery disconnect so there is no issue with leaving your cables plugged in; it will not drain the battery as long as the switch is in the "off" position.