Amazon.com: New Ultra Bass Processing Circuit-- Low-Pass Filter Board Finished for Amplifier : Electronics
Amazon.com: Preamp Board 2.1 Channel Low Pass Filter Subwoofer Independent Interfaces for Full Frequency and Bass Output Signals Tone Board HI FI Circuit Board DC 12-30V / AC 9-20V : Electronics
MXR M82 Bass Envelope Filter Effects Pedal | Guitar Center