Programmable Complex Waveform Generator

The 259t is the largest and most complex analogue oscillator from Don Buchla's legendary 200 modular synthesizer. The 259 originated the concept of the "Complex Oscillator" in the 1970s and has been reissued by Buchla & Tiptop Audio in Eurorack format. The module consists of two oscillators, called the Modulator and Principal, with a middle section that provides voltage control over the internal modulation paths between the two oscillators, resulting in highly complex timbres. Additionally, the principal oscillator passes through multiple unique voltage-controlled waveshapers and crossfaders for further signal processing. The module's pitch can be controlled with 1V / OCT or via its internal auto-tuner and ART control to create precisely pitched notes.

Both oscillators have a large Frequency control knob with a range of about 27.5hz which is the lowest A0 pitch on a piano up approximately 8 octaves to about 7040hz or A8 and octave above the highest A on a piano. The frequency figures surrounding the Frequency knob are approximate, not precise. As mentioned before their frequency ranges can be driven higher or lower with CV. There is also a fine tune knob which covers a range of about an interval of a fifth. Both oscillators have two CV inputs. The one with an attenuverter can add or invert the incoming CV. The one marked Keyboard or ART can toggle to Keyboard mode which use 1V/OCT, or to ART. Both oscillators can receive Audio FM and the amount of FM will be determined with the attenuator.

In Timbre/Harmonics section there are 3 wave shapers in that section and the knobs allow us to cross fade between their outputs and the VCO sine wave. The wave shapers are: Wave Folder Sawtooth M shape (can be consider as square) The Order knobs cross fade between wave folder and / sawtooth and M shape. It is the final cross fade before the output. When the Order is fully CCW the output is the wave folder and in that case the Timbre knob is the folding control and Symmetry adds DC to the audio entering the folder thus altering its folding further to be asymmetric. When Order is fully CW, timbre cross fade between the VCO sine wave and another cross fader of the sawtooth/M shape that is controlled by the Symmetry knob.

Since Order and Symmetry don’t have attenuators on their CV input this is good opportunity to use a 257t to process CV before going to these inputs for more subtle control. From the original manual: “These three waveshape controls have a tremendous eect on the Final output signal and should be experimented with to discover the wide range of timbres this oscillator can produce before any signal processing.”

PITCH CONTROL WITH ART

The pitch of the 259t oscillators can be controlled manually with 1V/OCT CV or automatically for higher note accuracy using the module's internal Autotune, activated by the ART switch. Please note that when set to ART, the CV FM inputs are disabled, while audio FM and all other inputs remain enabled