The Model 158 is a dual oscillator created out of an entirely discrete transistor core. It consists of two independent and identical sides each with a front panel tuning knob, a frequency modulation input and attenuator, and a knob to fade smoothly between saw and sine waves. The RED PANEL model 158 is based off of the original “A” variant of the 158 oscillator.
The 158 was one of the very first voltage controlled oscillators ever produced. As such it contains many particular quirks/rawness of this first generation of synthesis. The exponential scaling of the oscillator is far from accurate, there is no temperature compensation, quick changes in pitch produce a slewing effect, and the saw waveform only vaguely resembles a saw wave through part of its range. It is as accurate a recreation as we believe is possible with the components available today. We performed hundreds of listening tests to find suitable replacements for obsolete transistors, and hand select multiple transistors on each individual unit to ensure that they have the proper sound.