Humble Audio Quad Operator User manual

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!!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.
!!Features include:
!!One knob per function design for true ease of use
!!Any FM algorithm is possible via modulation matrix

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!!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.
!!Master Controls

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!!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
!!Operator Functions
!!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

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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
!!Saving an Algorithm. Long pressing on the A, B or C slot of the expander until its
LED blinks twice to save into that slot.
!!Selecting an Algorithm. Quick pressing an Algo slot’s button causes that Algo to
become the “right” in the crossfade. The previous “right” then becomes the “left” slot
in the crossfade. Thus, to effectively a new left and right simply quick press any two
slots you like. The the left and right may be the same slot. This is good, for instance,
to ensure that you are using only the live knob positions by double tapping the Live
slot.
!!When using A, B, or C slots without the Live slot, the positions of the “Mod x”
parameter knobs on the Quad Operator are ignored.
!!Connecting the Algo
!!We used a 15x2 pin header for connecting the Algo to the Quad Operator because
they’re cheaper and offthe shelf than 15x1. As long as you’re consistent in using the
same 15 pin edge on each header, the Algo will function properly. If you didn’t
connect it properly, the Algo simply will not light up and you’ll know you need to
adjust one of the headers. When first powered on, the Live slot LED will be light up
!!Algo Expander

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!!AR FM — the position into which to patch your modulation signal. Accepts audio
rate modulation sources.
!!Gain knob — modifies gain via analog input circuit to allow maximum gain while
avoiding clipping. Tuned to handle signals that range from +-5v to +-10v.
!!Clipping indicator LED — the red LED indicates that the input signal is being
clipped, leading to distortion of the input signal. Modify gain knob to reduce
clipping
!!Gain CV — affects the intensity with which external modulation source modifies
the frequency of the internal operators. Normals to a gain of 1 (signal is full
volume and modulation is static and active)
!!Mod 1-4 —Like each internal operator, the external modulation input comes with
4 modulation sends that determine the amount of frequency modulation each
operator receives from the external source at maximum gain
!!External Modulation Functions
!!Patching and Programming

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!!
!!The Quad Operator can be confusing at first. The multitude of parameters can easily
lead a user to noisy, dissonant outputs. This section provides some tips on obtaining
more restrained, harmonic results. It’s always easy to indulge in more aggressive and
harsh sounds from here.
!!
!!Set your parameters as described below as a good starting point. If a parameter
isn’t mentioned, it’s up to you and well within the bounds of normal frequency
modulation techniques.
!!Another way to thing about this list—these are the parameters you should modify
when you want to make sounds that are noisier, dissonant, and aggressive.
!!Set the VCO/LFO switch to VCO
!!Set all operators in lock state
!!All Detune knobs at 12 o’clock — this ensures integer frequency relationships
determined only by the Ratio knobs, which is essential for harmonic results in FM
!!All Shape knobs at full counterclockwise — start with sine waves, the classic FM
starting waveshape. Waveshapes with overtones together with modulation can
quickly add aliasing and noise, so it’s a good idea to start with no modulation and
go from there
!!All modulation sends at full counterclockwise — this turns offall modulation,
ensuring we have a “sane” beginning. Lots of modulation can add aliasing and
noise, so it’s a good idea to start with no modulation and go from there
!!
!!Patch Examples
**MORE INFORMATION HERE**
!!Achieving Harmonic Frequency Modulation Results
The Neutral Position
!!Translating Algorithms to Modulation Matrix
**MORE INFORMATION NEEDED**
!!User Maintenance

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!!
!!Read the Firmware Update Instructions Here
!!Calibration is important so that the v/o and ratio inputs (when an operator is running
in free state) accurately interpreting 1 volt changes. If you’re Quad Operator sounds
like it might not be tracking pitch properly on one of these inputs, try the calibration
procedure described here.
!!The Quad Operator is equipped with a precision DAC output, which allows it to
generate output signals for each operator output at precise voltages. This is
especially useful for calibrating the Quad Operator without an external precision
reference voltage. The Quad Operator can thus be calibrated with a simple feedback
patch and a few quick switch flips to trigger the calibration procedure.
!!Step 1: Patching the Module
!! :
!!“op 1” →“ratio 1”
!!“op 2” →“ratio 2”
!!“op 3” →“ratio 3”
!!“op 4” →“ratio 4” and “v/o” via an unbuffered splitter such a starfish or stackable
cables *
!!* It’s very important that “op 4” out is used for the split, not one of “op 1”, “op 2” or “op
3”. The calibration procedure does some extra compensation for this split. The
unbuffered split is important—a buffer splitter can apply a small amount of gain that
changes the output voltage, which will adversely affect the measurements taken
during calibration
!!Firmware Updates
Firmware updates can be loaded on the Quad Operator via a micro USB port located
on the back. The latest version of the firmware is version 1.0.4.
!!Calibration
Patch outputs back into inputs in the following manner

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!!Step 2: Triggering the Calibration Procedure
!!Once you’ve properly patched the module as described above, flipping the switches
according to the following “cheat code” to trigger the calibration procedure.
1. Flip operator 1’s free/lock switch one time
2. Flip operator 2’s free/lock switch one time
3. Flip operator 3’s free/lock switch one time
4. Flip operator 4’s free/lock switch one time
5. Flip the vco/lfo switch 5 times quickly
!!When the calibration procedure is triggered, the gain indicator LEDs will blink twice
before returning to normal operation within a few seconds.
!!Ratio and shape parameters are the aggregate of the knob and CV inputs. 5 volts of
CV range corresponds to a full turn of a knob. Thus, it’s possible to “turn” a knob
through it’s full range in either direction with a bipolar CV input (e.g., a fully
clockwise knob can be turned fully counterclockwise by applying a -5v CV signal).
!!Specifications
!!Parameter Ranges
Parameter Range
Coarse (VCO mode)16.35 Hz (C0) to 2093 Hz (C7)
Coarse (LFO mode)0.511 Hz (C-5) to 65.41 (C2)
Fine +/ - 6semitones relative to coarse tuning
Ratio 1-4(lock state)x1/11 to x11 relative to master coarse &
fine
Ratio 1-4(free state & VCO mode)16.35 Hz (C0) to 2093 Hz (C7)
Ratio 1-4(free state & LFO mode)0.511 Hz (C-5) to 65.41 (C2)

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!!Quad Operator
!!Width: 30hp
!!Depth: 25mm
!!+12V: 140mA, -12V: 13mA
!!Algo expander
!!Width: 4hp
Detune 1-4+/ - 6semitones
Shape Crossfades between sine, triangle, square,
sawtooth
Gain 1-40to 1gain multiplier
!!Signals Specifications
Patch Point Type Voltage Range Normal
Voltage
Sample
Rate
Reset Gate in 0v, 5v (threshold ~2.5v)0v6kHz
1V / Oct CV in -1v to 5v0v6kHz
LF FM CV in -5v to 5v0v6kHz
Ratio 1-4CV in -5v to 5v0v6kHz
Shape 1-4CV in -5v to 5v0v6kHz
Gain 1-4, Gain
AR FM
CV in 0v to 5v5v6kHz
AR FM Audio in Trimmable for ranges
between -5v to 5v and
-10v to 10v
0v48 kHz
Op 1-4Audio /
CV out
-5v to 5vn/a 48 kHz
!!Physical Dimensions and Current Consumption

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!!Depth: 25mm
!!+12V: 5mA, -12V: 0mA
!!Please address your questions and issues to us on our community forums so that
other users may benefit from the answers to your questions!
!!Humble Audio products are warranted for 12 months from date of purchase. If you’re
having an issue with your device that you’re unable to address via the community
forums, please contact us directly.
!!Customer Service and Support
Humble Audio Community Forum
Humble Audio Eurorack Modules
discourse.humble.audio
Humble Audio Community Forum • discourse.humble.audio
!!Warranty