Scorpio

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Applications

  • Creating robotic voices
  • Creating pitched percussion and rhythms
  • Transferring the spectral characteristics of one audio signal onto another over time

Description

Please note that Scorpio contains a large number of DSP objects and uses a significant amount of the ER-301's CPU. It is currently only advisable to use this unit on the 48kHz version of the firmware, where it uses average CPU of 60%.

Scorpio is a 10-band, monophonic vocoder. A vocoder is an audio processor that captures the characteristic elements of an an audio signal (known as the modulator) and then uses this characteristic signal to affect another audio signal (known as the carrier).

To start, send an audio rate signal (the modulator) into the input of Scorpio. Insert an audio rate signal (the carrier) into the carrier control's subchain. You can use external signals (such as from INx), or create these signals internally in the ER-301. Scorpio is a monophonic vocoder, but can be used in a stereo chain. In a stereo chain, the right channel of the unit input (the modulator) is discarded, and the left is vocoded. In a stereo chain, the unit outputs identical vocoded signals to both the left and right channels for further stereo processing.

Find out more and join the discussion of this bespoke unit in the forum

Parameters

Standard

The following standard controls are available.

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carrier

Control Type Has Sub-chain? Fader Range Fader Scale
Simple Fader no yes -60dB to +12dB

The carrier signal goes into the subchain of the carrier control. You can use the external inputs INx, ABCDx, or create the signal chain with in the ER-301 (or a combination). You can also insert mixers into this subchain to mix internal and external signals.

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The most effective carriers have a large amount of spectral content. For example, a sine oscillator, which contains only the fundamental harmonic, is a poor choice. A saw wave which contains even and odd harmonics is a better choice. A stacked detuned saw wave will yield better results still. A stacked, detuned saw wave chord has even more spectral content. White, pink, or velvet noise may also yield good results, as well as other sampled or synthesized waves.


envelope

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Gain/Bias yes gain (-10 to 10)

bias (0s to 1s)

time in seconds

The envelope control adjusts both the attack and release time of the envelope follower connected to each of the 10 input band pass filters. Very short times (around 30ms) result in a more clearly defined vocoded signal. However, very short times may result in ring modulation, which will likely manifest as an undesirable effect. Longer times tend to blur the clarity of the vocoding, which can be a desirable effect, depending on your goals.

fshift

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Pitch yes transpose (-3600¢ to 3600¢) logarithmic ratio

The fshift parameter sets the amount by which the center/fundamental frequencies of the output filters are are offset from the fundamental frequencies of the input filters. At zero cents, the modulator is "transcribed" onto the carrier at the same frequency bands. Adjusting this control causes a timbral shift in the vocoded signal, as it tends to excite higher or lower frequencies in the carrier. It can be used for subtle adjustments in clarity or more extreme effects. Since it is a V/Oct control, it can be sequenced or played with a V/Oct tuned controller.

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Note that fshift controls the fundamental frequency of Scorpio's output filters, and will not change the pitch of your carrier.


postgain

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Gain/Bias yes gain (0 to 10)

bias (-5 to 5)

linear

If Scorpio's output is too high or too low, this parameter adjusts the level of the vocoded signal by applying gain after the vocoded signal but prior to the modulator mix in (modmix).

modmix

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Gain/Bias yes gain (-10 to 10)

bias (-60dB to 12db)

logarithmic gain

This control mixes a high-passed copy of the modulator back into the vocoded signal. It can add clarity to the signal by allowing plosives and transients present in the modulator to mix (in unvocoded form) with the vocoded carrier. By adjusting the hpModf0 control to a low value, you can mix a more full spectrum version of the modulator back into the output signal.

Frequency Controls

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To view the frequency controls, focus press on the unit header, and set the option "Display frequency controls?" to yes. The frequency controls will appear to the right of the standard controls.

ScorpioFrequencyControls.png

hpModf0

Control Type Has Sub-chain? Fader Range Fader Scale
Simple Fader no 5 octaves above and below 440Hz frequency in Hertz

The hpModf0 control sets the fundamental frequency for the high-pass filtered copy of the modulator signal which is mixed into the final signal by the control modmix. Typically, you would want to leave this frequency set very high so that only plosives and transients from the modulator get mixed back in with the output. However, setting this value lower may be useful with percussive signals or with robotic vocals if the modulator is "singing in tune" with the carrier.

Resonance - qIn and qOut

Control Type Has Sub-chain? Sub-chain Parameters Fader Scale
Gain/Bias yes gain (-10 to 10)

bias (0 to 1)

linear

Changes the amount of resonance on all of the input or output filters as a group. Adjusting the resonance can increase (or decrease) the clarity of the signal, and can also change the timbre of the output signal. The resonance is adjusted for the input and output separately, but for all 10 bands of each together.


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Scorpio is constructed from resonant four-pole high and low pass filters. Increasing the resonance too much can cause the filters to self-oscillate which can cause the unit to output signal even if the modulator is silent, and can also cause the output to clip.


f1 - f10

Control Type Has Sub-chain? Fader Range Fader Scale
Simple Fader no 5 octaves above and below 440Hz frequency in Hertz

The f1 through f10 controls adjust the center/fundamental frequencies for each vocoder band separately - the matching filter band on the input and the output are both adjusted together. Making adjustments to these controls may result in more (or less) clarity in the vocoded output, as well as change the character/timbre of the vocoded sound. They can be used to "focus in" on certain frequencies of the modulator for vocoding.