Darkglass Tone Capsule active 3 way preamp for bass.
Aguilar OBP-1 bass preamp. boost-only bass and treble controls, 9v or 18v wiring.
Aguilar OBP-3 SK/PP preamp for bass. Bass, Mid and Treble boost/cut controls with push/pull pot to change the mid frequency.
Aguilar OBP-3 TK preamp for bass. Bass, Mid, Treble boost/cut control with three knobs.
Boston SJ-3 Stereo Jack Input
Taurus TM1 Preamp 3 band active EQ for bass. Punch and DBS filters, 9v or 18v.
All Parts Stereo Input Jack.