The design philosophy for this circuit was centered on replacing all of the op-amp circuitry found in the earlier circuits with discrete transistors and LC filters. The previous circuits had many (high quality) op-amps in series, this resulted in audible distortion, especially on `ess` sounds. The discrete transistor amplification stages in this design produce an audio signal with much lower levels of distortion.
To make alignment of the stereo modulator easy, first build this Stereo Test Tone Generator, or generate equivalent waveforms with standard test equipment. The circuit produces a number of waveform combinations that are necessary for adjusting this circui