Model 158

Dual Channel Oscillator

Perhaps the most delicious FM ever! – The Dual Sine-Sawtooth Generator is based on Model 158, a circuit known from the Buchla 100 series. The module features two VCOs with a discrete transistor core design. Their beefy vintage sound is very charming. True to the original, you can crossfade continuously between sine and saw tooth waveforms. The tuning ranges from low frequency to ultrasonic sound. Thanks to two outputs per VCO, it is not only possible to do FM patches, but cross modulation patches as well. The results can sound wet, scratchy or hollow, sometimes even vocal-like.

We have to admit: On paper, the Dual Sine-Sawtooth Generator looks as interesting as stale bread. However, if you hear the module, you’ll fall in love immediately. Its full-bodied, sometimes harsh sound is already impressive in its raw state. Potentiometers can be used to transform sine into saw waves. For playing the circuit, there’s a 1v / octave input per VCO. The pitch tracking isn’t perfect, but much better than with the Buchla original. The irregularities are not negative in any way, even when playing over a range of several octaves. Rather, the pitch deviations contribute to the hearty vintage character of the Dual Sine-Sawtooth generator.

For tuning the oscillators manually, there are two large, very handy potentiometers. That said, it should be noted that you can use either the knobs or the 1 v / octave inputs. – Not both at the same time. A switch decides whether the potentiometers or the connectors are active. For those who do not want to miss out on manual tuning options while using pitch CV signals, we recommend adding a Model 156M CV-Prozessor to the setup. – It is basically a front-end for the Model 158.

Waveforms are emitted via two outputs per VCO. Thanks to the dual concept, audio material can be send to other modules, for instance a filter or wave shaper, and to the exponential FM input of the respectively other oscillator at the same time. This is the ultimate strength of the Dual Sine-Sawtooth Generator, as frequency and cross-modulation patches sound extremely fat. Thanks to attenuators, the strength of FM effects can be adjusted comfortably.

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