Simple Audio Amplifier/Oscilator Circuit with Two Transistors

simple audio amplifier circuit with two transistors

This circuit has two main functions, namely as an audio amplifier and as an oscillator. J1 is a standard 3.5 mm jack connector. The transformers used in this circuit are Argonne AR-164, Thordarson TR-114, or Stancor TA-42. If all the transformers are not available, any output transformer type can be placed.

The speakers needed for this amplifier/oscillator circuit are 8 ohms type, with a size of 6 inches. If it will be used as an oscillator that emits a sound frequency tone, you just ON the pushbutton as it appears on the figure. But if it will only be used as an amplifier, you can eliminate KEY button and C1 switch.

The 2N104 and 2N408 transistors work best when supplied with a 6 VDC voltage supply from the battery. The 10K potentiometer is perfect for controlling volume.

Parts List:


  • Q1 : 2N104
  • Q2 : 2N408


  • R1 : 500 ohm
  • R2 : 10K potentiometer


  • C1 : 0.01


  • T1 : Argonne AR-164, Thordarson TR-114, org Stancor TA-42
  • Speakers: 8 ohm 6 inch
  • J1 : Standard phono jack
  • B1 : 6 Volts
  • S1 : SPST key