Amazon.com: EMG BQC 4-knob Active Bass Preamp System : Musical Instruments
Fosi Audio P1 Tube Pre-Amplifier Mini Hi-Fi Stereo Buffer Preamp 6J1 Valve & Vacuum Pre-amp with Treble & Bass Tone Control for Home Theater System(with Power Supply) : Amazon.ca: Electronics
Amazon.com: Guyker 2-Band Preamp/Tone Control with Adjustable Gain for JB Bass (with Jazz Bass Control Plate, Dome Control Knobs and Stacked Knob) : Musical Instruments
Amazon.com: MXR M80 Bass D.I.+ Bass Guitar Preamp Distortion Pedal with Footswitchable Distortion Channel, Noise Gate and XLR Direct Out with 2 Path Cable and 2 Instrument Cable : Musical Instruments