This is an audio amplifier for a small speaker. Large potentiometers were used to attach knobs for manual control. Power terminal will connect to a DC jack mounted at the back of the enclosure for external 9V DC power supply. Speaker terminal will connect to a small 2.5" speaker at the front of the enclosure. Signal terminal will connect to a 3.5mm jack mounted at the back of the enclosure.
C2, C5, C7
Audio In, 9V DC Power In, Speaker Out
Bass Boost, Gain, Volume