The master mixer circuit is a series of buffers and an increase in the audio signal gain which can be adjusted by the volume pot. The master mixer is classified as an active circuit that uses a dual op-amp IC and the voltage used is 12 volts. In addition, to amplify the sound that usually sounds very weak/small when inputted to the amplifier, and also as an amplifier from other weak audio sources.
This kit is widely applied to power amplifiers so that the sound will kick even more.
This circuit is very helpful and makes your Power Amp louder.
PCB Layout Master Mixer Single Supply 12VDC Fixed, The layout of resistors that have no value can be filled as desired, for example, 1K Ohm - 10K Ohm, the resistor affects the gain.