Low THD oscillator for audio tests
Sine wave generators are used in audio measurements. For a distortion measurement of speakers, most simple generators are sufficient, as the level of distortion is not very low. This is different for measurment of audio amplifiers. Here the distortion can be very low, which requires a sine signal with significanlty lower distortion that the measurement object. Even professional measurement equipment is limited here.
A sine wave oscillator for a 1 kHz signal with lowest distortion possible was developed based on a Wien bridge. The result is a oscillator with -133 dB THD.