Quad Operator Manual
The Quad Operator offers 4 variable waveshape operators for linear FM synthesis. Implementing frequency modulation synthesis completely from scratch in firmware, the Quad Operator is able to provide a modern take on frequency modulation synthesis.
- One knob per function design for true ease of use
- Any FM algorithm is possible via modulation matrix
- The Algo expander provides algorithm save/recall and crossfading capabilities
- Independent output per operator
- Virtual VCA per operator for both animating modulation and output volume control
- Includes a dedicated “AR FM” input with its own modulation sends, designed to bring an audio rate signal in from your rack for use as a modulator. Try processing a phase locked operator, and feeding it back in!
- Each operator can also be unlocked then tuned and patched independently, making the module a great general purpose oscillator bank
- Convincing digital emulation of classic analog waveshapes—sine, triangle, square, and saw
- An LFO mode, enabled the generation of phase locked, complex modulation signals
Where the unexpanded Quad Operator maintains a one knob per function design discipline, we nevertheless recognized the value of some more advanced algorithm-oriented functionality.
The Algo expander for the Quad Operator provides:
- Saving and loading of modulation send knob positions for FM algorithm design reuse
- Crossfade between pairs of saved algorithms, or a saved algorithm and the live knob positions
Coarse knob — master tuning like most module oscillators. Affects all operators in lock state. Follows exponential curve through 8 octaves (1 degree of turn results in same amount of change in tones regardless of position).
Fine knob — + / - 6 semitones of control relative to frequency defined by coarse.
VCO / LFO switch — Affects the base frequency of the coarse tuning control
1V / Oct CV — 1 volt per octave frequency control over all operators in lock state
LF FM CV — + / - 6 semitones of frequency modulation best for low frequency rate CV effects like vibrato, bends, pitch envelops, etc.
AR FM — Audio rate input that allows you to use signals from your rack as modulators. Especially useful for feedback patches with lock mode operators.
Reset CV — trigger input for resetting all operators phase. Great when using quad operator as a modulation source. operator’s lock versus free state does not affect behavior
Lock Versus Free State
In lock state, each operator adheres to a strict integer frequency ratio relationship to the master coarse and fine tuning. This is the state in which you will want to keep your operators for most classic FM sounds. This is essential to achieving waveshapes with harmonic overtones. The detune control remains available for introducing subtle as well as extreme inharmonic effects.
In free state, each operator essentially becomes its own independent oscillator. The ratio knob becomes a coarse tuning control, and ratio CV becomes 1 volt per octave control for the operator. With modulations all at 0, this allows you to use each operator as its own oscillator in up to 4 independent patches. Modulation nevertheless remains intact if you wish to use it. Without frequency / phase locking, frequency modulations will tend to be inharmonic.
Knobs and Control Voltage
- Ratio knob & CV — two modes:
- Lock state — 1/11th to 11 multiplier relative to master coarse/fine in integer steps
- Free state — knob is continuous coarse tuning for the operator, CV is 1 volt per octave
- Detune knob — + / - 6 semitones of continuous fine tuning
- Shape knob & CV — continuously variable shape from sine>triangle>square>saw
- Gain CV — affects both the output level of the operator signal as well as how intensely it modulates other operators via its modulation sends. Normals to gain of 1 (signal is full volume and modulation is static and active)
- Mod 1-4 — Affects how intensely the operator modulates the frequency of other operators, (including itself) at maximum gain. Think of each as a modulation send—when you turn up “Mod 1”, you are send modulation from the source in that row to Operator 1
The Algo expander allows you to save and crossfade between values of the modulation matrix parameters—all the positions of the “Mod x” knobs for each of the 4 operators and the AR FM input. Conceptually, you can think of each slot is equivalent to an algorithm in the parlance of classic FM synthesizers. The Algo provides 3 save slots—A, B, and C as well as the Live slot which represents the current true modulation knobs.
Using the Algo