Resonators

Resonators

The Resonators section is one of the original instrument's most unique features. It consists of three state-variable filters in a parallel configuration. The parallel routing means the signal is split and runs into all three filters with their collective outputs summed together. Cranking up the Emph controls (aka, resonance) for each band can create three individual "peaks" or resonances, hence the "resonator" name. 

Another unusual aspect of the original Resonators section is that each is band-limited. Most synthesizer filters are configured such that the cutoff frequency covers the entire audible sound spectrum (20-20,000 Hz, give or take), whereas each of the three resonators cover a "slice" of the audio spectrum, i.e. low, med, and high frequencies as follows:

• Low: 60 - 300 Hz

• Med: 300 - 1500 Hz

• High: 1500 - 7500 Hz

The original Resonators section has two major shortcomings: the filter slopes are a little too shallow to create really dramatic resonance effects, and the cutoff frequencies aren't CV controllable. We've addressed both of these issues with a 12/24 db slope selector, as well as bipolar CV inputs for each cutoff frequency

The Resonators section excels at creating formant-type sounds, and is also great at emulating phaser-type sounds when its cutoff frequencies are swept via CV modulation.

Pass Mode - Globally selects the behavior of all three filters.

• Lowpass: Allows frequencies below the cutoff frequency setting to pass through,

• Bandpass: Combines both lowpass and highpass modes, leaving sound only in the middle of the audio spectrum. The cutoff frequency lies roughly halfway between the slope falloff on either side. 

• Highpass: Allows frequencies above the cutoff frequency setting to pass through

• Notch: The opposite of a bandpass filter; a notch filter removes a narrow band frequencies in the middle of the audio spectrum, but leaves frequencies above and below unaffected. This might not sound all that useful, but modulating the cutoff frequency of a notch filter creates an effect similar (but not exactly the same) to a phaser. Stacking all three Resonator stages emphasizes the effect.

Slope- The nature of how a filter works is that frequencies "fall off" above or below the cutoff frequency. Slope adjusts the steepness of this falloff, hence the "slope" terminology. A 12db per/octave filter has a shallower slope, giving it a clearer and brighter character, whereas a 24db per/octave filter's steeper slope gives it a tighter and darker tone and far more pronounced ringing characteristic when the Emph slider is turned up.

Since the controls for the Low, Med, and High sections are the same other than frequency range, we'll explain them once:

CF (Cutoff Frequency)- Sets the frequency where attenuation begins. Attenuation will be above or below this frequency (or both) depending on the Pass Mode switch setting.

Emph (Resonance)- Emphasizes sound energy at and around the current cutoff frequency by adding feedback from the filter's output back to its input. At lower settings, this can be used to create mild resonances such as those heard in acoustic instruments. At more extreme settings, resonance can create a pure sine wave at its own frequency (variable via the CF slider). Be careful with the Emph sliders as they can get loud at extreme settings (you can easily control this using each section's Gain slider). Note that this "ringing" resonant frequency is much more prominent with the Slope switch in the 24db position.

Gain- This acts as a volume control for each resonator section. Resonator sections can be muted by setting their Gain control to 0%.

Mod- Rate/Amount- The Resonators section on the original sounds really awesome when you sweep cutoff frequency sliders, but the sliders can't be voltage controlled. It sounds so nifty that we added a dedicated triangle-wave LFO, much like the FM and shape mod LFO's built into the oscillators. Of course the Resonators cutoff frequencies can also be modulated with Modulator 1 and Modulator 2 via the Mod Source buttons and attenuators explained below, but the dedicated LFO means you won't have to "waste" one of the extra modulators, and it makes modulating the Resonators section fast and simple.

• Rate- Sets the LFO mod speed from 0.05-10 Hz.

• Amount - Sets the mod depth from 0 to 100%.

Note that the Mod controls affect all three resonator sections equally. If you'd like to modulate the Resonators' individual sections separately, use the Mod Source buttons and attenuator knobs.

Mod Source buttons and Attenuator knobs- The Mod Src selector buttons and attenuators beneath the sliders allow positive or inverted voltage control of the slider directly above. Clicking the Mod Src selector button opens a pop-up menu where the mod source can be selected. Once a mod source is chosen, the button turns red and its text changes to indicate the current mod source. To choose a different mod source, click the button and choose another modulator, or choose None to disable modulation. The attenuator knobs beneath the Mod Src buttons set a positive or inverted voltage control amount for the controls.