Very simple mixer circuit bc457 3 of passive elements (resistors, capacitors) consists of four channels have input dc voltage between 9 … 16 works with a 9 volt battery can be used with
NPN transistors can be bc 547/548/549 or 2n2222 etc … any small signal NPN appropriate, simply follow the B / C / E as you plant them one! Japanese example 2SC945! MPSA06
Simple Mixer Circuit Schematic PCB
Guitar Preamp Effect Circuit
Prepare a musician playing a guitar preamp tone control circuit “gain, deep, press, bass, treble, medium” and make controls debra opamf TL072 JFET transistors on the board.
Supply voltage 12 volts dc. 4 amp 12v battery and circuit performance would be better if you can use the parts list diagram drawing PCBs are
Guitar Preamp Effect