Phase Displacement Oscillator (PDO)

This hybrid VCO has all the feel of an analog VCO but with the benefits of digital waveshaping. The PDO will easily find a home in your system! 

The PDO exists to utilize the phenomenon of Phase Modulation (PM). This allows for the relative phase difference of its outputs to be set or modulated, producing very interesting sounds. The result is similar to Frequency Modulation (FM) but affects the output to a greater degree without affecting the stability of the initial frequency. 

PM has the same benefits of quadrature filters/sine wave generators and greatly exceeds their capabilities at audio rate modulations. PM is highly useful for for creating metallic and bell tones and very controlled harmonic interactions. 

Because PM affects the relative phase and not the frequency of the waveform generated, the PDO can self modulate its PM inputs. Thils creates complex harmonic signals that seem to vary in frequency but are quite stable. 

Phase Modulation is also quite powerful when using the PDO as an LFO. Adjusting the relative phase of each output allows for very precise modulation of other modules. Each output can have any of the available waveforms simultaniously. There is a myriad of modulation possible with the PDO!

Features: 

• Analog Sawcore VCO 
• Temperature Compensated
• Linear (AC/DC) & Expo (DC) FM
• Bipolar Attenuators for FM
• Calibrated 1V/Oct Input
• Hard Sync Input (LFO Reset)
• ~.0012Hz (14min) to >=10kHz
• Digital Waveshaper
• Four Simultanious Outputs
• Phase Modulation for Outputs 2,3,4
• Bipolar CV Inputs for Phase Mod
• Any waveform on any output
• 14 Bit Input, 12 bit Output
• 100kHz Sample Rate
• Channel Indicator LEDs
• Sum output of all channels
• Expandable
• 10HP, +115mA -40mA Power Draw

Controls and I/O:

The PDO's analog VCO should feel familiar and intuitive. 

1V/Oct Input - Calibrated input for pitch control. The VCO will track at least 5 octaves using this input. 

Sync Input - Rising edge sawtooth reset/sync input. Does not affect slope of sawtooth. Use as LFO reset also. 

Coarse & Fine Knobs - Coarse knob adjusts the frequency of the VCO throughout its full range. Use the Fine knob to tune the oscillator within approximately 1/3 octave range. 

Exp FM - This input jack and bipolar attenuator provide exponential FM to the VCO. This input is DC coupled.

Lin FM - This input jack and bipolar attenuator provide linear FM to the VCO. This input can be DC or AC coupled. A jumper on the back enables DC coupling when in place. We recommend AC coupling to prevent frequency shift caused by the bipolar attenuator's offset voltage.

Phase Modulation Inputs (Φ)

Phase Inputs (ΦCV) - The PDO has three phase inputs, one for each channel: 2, 3 and 4. These inputs can use any type of signal. Each phase input has a bipolar attenuator, turned CW past center for positive modulation, turned CCW past center for inverse modulation. 

Phase Offset (Φ) - These controls set the relative phase of each channel, from 0 degrees to + or - 360 degrees. This control is added to the ΦCV input and acts as a bias level control when there is an input.

Outputs

Out1 - Out4 - These are the outputs for each channel, the current level is displayed at the top of the module by a green LED. 

Sum Output - This output takes all four of the outputs and sums them together. Out2 and Out3 are always summed to this output. Out1 and Out4 are normaled through the jack. So plugging into Out1 or Out4 will remove that signal from the Sum Output.

Staircase Output (SC Out) - This output jack is the result of the relative phases of the three phase input channels compared to the analog sawtooth waveform. It forms a staircase type output (multiple square waves added together).

Expansions