Amazon.com: Remo RemO's Tone Control Rings - 10", 12", 13", 16" : Musical Instruments
Simple Audio Tone Control Circuit
AIYIMA Pre amplifier Tone Board UPC4570C OP AMP Stereo Preamplifier Volume Tone Control Super OPA2604 AD827JN With LM317+LM337|tone control board|volume tone control boardstereo preamp - AliExpress