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Amazon.com: Bazooka RBCM-100 Remote Bass Control for Bazooka Base Tubes: Car Electronics
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Amazon.com: Nobsound Auto Car Amplifier Audio Subwoofer Bass Control Knob Sub Gain Equalizer Regulator Frequency Controller RCA Line Level Adjust: Car Electronics
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With new equalizer feature, Amazon Echo devices get bass and treble control - GeekWire