Myriad Player’s Guide
What does Myriad do?
Myriad is an oscillator designed for the creation of big, complex, dynamic sounds. At the heart of Myriad, nine oscillators mix, detune and intermodulate together to create complexity, motion and stereo width. Meta-modulation algorithms add more life and movement. Analog waveshaping and overdrive circuits distort and modulate the tone of the oscillators. Five CV inputs give you flexible control options.
Signal Chain
flowchart TB
subgraph O1["Oscillators 1"]
Osc1["Osc1"]
Osc2["Osc2"]
Osc3["Osc3"]
end
subgraph O2["Oscillators 2"]
Osc4["Osc4"]
Osc5["Osc5"]
Osc6["Osc6"]
end
subgraph O3["Oscillators 3"]
Osc7["Osc7"]
Osc8["Osc8"]
Osc9["Osc9"]
end
O1 --> VL["VCA Left"] & VR["VCA Right"]
O2 --> VL & VR
O3 --> VL & VR
VL --> WL["Waveshaping Left"]
VR --> WR["Waveshaping Right"]
WL --> DL["Overdrive Left"]
WR --> DR["Overdrive Right"]
VL ----> COL(["Clean Output Left"])
VR ----> COR(["Clean Output Right"]) & COL
DL --> SOL(["Shaped Output Left"])
DR --> SOR(["Shaped Output Right"]) & SOL
Osc1:::gen
Osc2:::gen
Osc3:::gen
Osc4:::gen
Osc5:::gen
Osc6:::gen
Osc7:::gen
Osc8:::gen
Osc9:::gen
VL:::gen
VR:::gen
WL:::gen
WR:::gen
DL:::gen
DR:::gen
COL:::gen
COR:::gen
SOL:::gen
SOR:::gen
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style O1 stroke:#000000,fill:#FFFFFF,color:#000000
style O2 stroke:#000000,fill:#FFFFFF,color:#000000
style O3 stroke:#000000,fill:#FFFFFF,color:#000000
Patching
Outputs
Myriad has two sets of stereo outputs. The first set is the clean signal, taken from the signal chain before the waveshaping and overdrive section. The second set is the shaped outputs that result from the waveshaping and overdrive. In each set, the nine oscillators are split, sending four to the left and five to the right channels. If you plug into a left channel only, then you receive a mono sum of all nine oscillators. If you patch into the corresponding right channel, then this splits the oscillators across the two channels. It’s possible to use all of channels or a mixture of clean and shaped at the same time.
Inputs
VCA
There is a control voltage input (0-5V) for the VCA. For the clean outputs, it simply modulates the volume level of the oscillators. For the shaped outputs, it works in tandem with the drivecontrol to add warmth and overdrive to the signal (see waveshaping and overdrive)
Attenuverted Inputs
The other four inputs (1V/Oct, Spread, ϵ, Interval) map to the lupin coloured knobs. All of these inputs are bipolar (-5V to +5V) and attenverted. Attenverting inputs allow you to scale and invert the incoming CV signal. When turned all the way to the right, the signal is passed through without change. As you turn towards the centre this reduces the scale of the signal towards 0. Turning the knob from the centre towards the left scales up the signal, but also inverts it i.e. multiplies it by a negative number. When there’s nothing plugged into these inputs, a constant 5V signal is sent to the attenvertor, meaning than moving the knob gives you a signal in the range of -5V to +5V.
Controls
Oscillator Controls
Frequency
Controls the base frequency of the oscillators (see the tuning). Calculation of the frequencies of the nine oscillators depend on this frequency, along with spread, interval and meta-modulation.
Spread
This controls how much the oscillators are detuned from each other. The mapping range allows from small or subtle beating, to wider discordant frequency intervals.
ϵ
Each oscillator model might react in a different manner to this control. See oscilator models for more info.
Interval
This control changes how the pitch of the oscillators is spread across octaves, relative to the fundamental frequency set by the 1V/Oct control. All three oscillators in each bank will always share the same interval setting. This allows you to build up sounds with different tonality in each octave.
In the central position, there is no modification. As you move the control left or right, you move across different settings, which are different combinations of how the oscillators spread in pitch.
To the left of centre, the mappings spread lower and then higher compared to the fundamental. To the right of centre, the mappings spread out in both directions from the fundamental.
Waveshaping and Overdrive
The waveshaping section is controlled by the blue-capped knobs, VCA/Shape and Drive. These two controls work in tandem to add warmth and dirt to the sound. This circuitry they control consists of a two-stage wave folder followed by an overdrive.
Waveshaping
The waveshaper, when driven by the VCA, folds the signal over a certain threshold. For simple waveforms, this adds harmonics. For complex waveforms (e.g. with significant detuning), the waveshaper can act in intersting, noisy and unpredictable ways. The amount of waveshaping is determined by the VCA.
Overdrive
The overdrive section clips the signal using the pink and blue LEDs visible through the front panel. This clipping creates extra harmonics. Like the waveshaper, the overdrive can behave in unpredictable ways when processing complex intermodulating signals. The level of overdrive is controlled by the drive knob.
Digital Controls
---
config:
layout: elk
---
flowchart TB
subgraph key["Key"]
keyA[" "]
keyTurn["Turn Encoder"]
keyPush["Push Encoder"]
end
subgraph Tuning["Tuning"]
direction TB
toct["Octave"]
tun["Tuning Screen"]
tsemi["Semitone"]
tcent["Cent"]
pbypass["Bypass"]
end
subgraph subGraph1["Oscillator Models"]
direction LR
osc1["Oscillator Model 1"]
A["Oscillator Screen"]
osc2["Oscillator Model 2"]
osc3["Oscillator Model 3"]
end
subgraph subGraph2["Meta Modulation"]
direction TB
mods["Modulation Speed"]
B["Meta Modulation Screen"]
modmode["Modulation Mode"]
modd["Modulation Depth"]
end
subgraph utility["Utility"]
util["Utility Screen"]
save["Save"]
end
keyA -- encoder --o keyTurn
keyA -- encoder --x keyPush
A x-- Y ----x B
A x-- Z ------x tun
tun -- X --o toct
tun -- Y --o tsemi
tun -- Z --o tcent
tun -- X --x pbypass
A -- X --o osc1
A -- Y --o osc2
A -- Z --o osc3
B -- X --o mods
B -- Y --o modmode
B -- Z --o modd
A -- X --x util
util -- Z --x save
save ----> A
keyTurn:::defc
keyPush:::defc
toct:::defc
tun:::defc
tsemi:::defc
tcent:::defc
pbypass:::defc
osc1:::defc
A:::defc
osc2:::defc
osc3:::defc
mods:::defc
B:::defc
modmode:::defc
modd:::defc
tpull:::defc
tnotes:::defc
util:::defc
save:::defc
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style subGraph1 stroke:#000000,fill:transparent,color:#000000
style subGraph2 stroke:#000000,fill:transparent,color:#000000
style Tuning stroke:#000000,fill:transparent,color:#000000
style quantise stroke:#000000,fill:transparent,color:#000000
style utility stroke:#000000,fill:transparent,color:#000000
style key stroke:#000000,fill:transparent,color:#333333
Visuals
Overdrive LEDs
The overdrive circuitry uses LEDs to help create distortion and warmth. Each stereo channel has two LEDs (pink and blue) which clip the signal when over or under certain voltages. These LEDs are visible through the front panel.
Screens
There are two main screens, alternated by pushing the Y encoder.
Oscillator Screen
This shows information on the currently selected oscillator models for each bank, and also shows a visualisation of the relative frequencies of the oscillators. Each of the nine oscillators is represented by a rotating line ending with a circle. The colour of the line matches the bank to which the oscillator belongs. The line rotates at a speed that increates with the frequency of the oscillator.
Meta-Modulation Screens
Each meta-modulator shows a visualisation of its algorithm. Rotating X changes the speed and possibly other variables of the algorithm. Rotating Z changes the depth of modulation.
Tuning
Tuning is centred on C1 at 0V, and is sensitive in a 10V range from C-4 to C6.
Incoming control voltages are attenuverted, so if the incoming pitch range is centred around 0V, then the attenuverter will be able effectively invert and scale pitch CV. If the voltage range is not centred around 0V, this will skew the effects of the attenuverter. Either way, if the attenverter is set all the way to 100%, then the incoming pitch CV will be directly reflected in the frequency of the oscillators.
Press Z to enter Tuning mode from Oscillator mode. Press it again to exit.”
The tuning screen allows adjustment of octaves, semitones and cents. These settings will affect both incoming pitch CV and also the effect of the frequenc control. Tuning can be bypassed
When exiting the Tuning screen, the settings are saved to flash memory and will persist after power cycles. While saving there may be a small audio pause while the processor writes the data.
Stereo Image
Myriad takes an unconventional approach to stereo imaging: the stereo field is created by tonal differences and intermodulation between the nine oscillators, and by analog sound processing. Four oscillators are sent to the left channel, and the remaining five to the right. With spread and interval controls set to 0, and all three banks set to the same model, the image will be effectively mono. As the differences across the models widens, so might the stereo image. The stereo image can be influenced as follows:
Use a mixture of oscillator models
This will send mixed waveforms to each channel, creating differences between the two sides.
Using the spread control
This will alter the balance of frequencies in each channel. Intermodulation between these frequencies will create panning effects
Using the interval control
This will create wider frequency variation across the oscillators in each channel, and therefore bigger difference across the stereo field.
Using VCA and Drive
The shaped outputs can be very nonlinear, and therefore accentuate intermodulation products between the two channels. These products create subtle to strong panning, and can be controlled by the VCA level and overdrive level. The panning is visible in the overdrive LEDs.
Saving State
Myriad can preserve it’s current state so that it’s loaded when you next power on the module. The state consists of:
- Choice of model for each oscillator bank
- Choice of meta-modulator
- Meta-modulator depth, speed and modulation target.
Press X from the oscillator screen to open the Utility screen, and then press Z to save. When you save, you may hear a small glitch in the audio, This is because the microcontroller needs to pause other processes in order to safely write to the flash memory on the PCB.