Stereo Test Tone Generator

This circuit produces two audio frequency sine waves with different frequencies but equal amplitudes. It can be used for testing a variety of stereo audio equipment. The circuit was originally developed the purpose of aligning an FM Stereo Modulator, like the type used in low power FM stereo transmitters. Two tone outputs are available, the low tone has a secondary output that is 180 degrees out of phase with the primary output. The circuit is also handy for testing computer sound card inputs. A variety of waveform configurations can be produced by plugging a stereo audio patch cord into the four output jacks.