Exciter

1. Pulse/Noise Selector Switches between pulse and noise mode
2. Trig/Env Input Main input. Connect a trigger, gate, or envelope (in noise mode only) to activate the exciter.
3. Vel Input Amplitude modulation input, designed to be connected to the Keyboard Vel output. Modulation depth can be adjusted with the knob.
4. External Audio Input Any audio signal connected here will be mixed with the exciter pulse or noise.
5. Pitch Input Main module pitch input, used by the exciter for filter frequency tracking.
6. Freq Knob Adjusts the cutoff frequency of the built-in low-pass filter.
7. Color Knob Changes the frequency response of the built-in filter. See (#filtercolor).
8. Freq Mod Knob Controls amount of pitch tracking for the filter cutoff frequency.

Overview ⚓︎

The Exciter is not a standalone module, but rather a shared section of Objeq Oscillator and Tube Oscillator, where its purpose is to trigger the physical models found in those modules.

Usage ⚓︎

The exciter has two modes, pulse and noise, as well as an external audio input. The physical model will not produce sound until either a pulse is triggered, noise is generated, or an external audio signal is present at the Ext Audio input.

Pulse ⚓︎

In Pulse mode, a very short filtered pulse is triggered every time a gate or trigger is detected on the Trig/Env input. This can be used to simulate a mallet, hammer, or plectrum, to create percussive, piano-like, or plucked sounds.

Connect a Keyboard Trig output or sequencer Gate output to the Exciter to trigger the pulse.

Noise ⚓︎

In noise mode, the Exciter generates filtered white noise. Depending on the filter and physical model settings, it can approximate a bow or an air jet. The amplitude of the noise is controlled by the envelope signal connected to the Trig/Env input.

When exploring the different sounds that can be produced by a physical model, it can be a good idea to start by connecting a gate signal to the Trig/Env input. It will work both as a trigger in Pulse mode and as a very basic envelope in Noise mode. When you have found a sound you like, you can then replace the gate with either a trigger or a more refined envelope depending on the exciter mode.

Noise mode also supports a trigger signal on the Trig/Env input. When a short trigger is detected, a short burst of noise will be generated. This can be used instead of Pulse mode to add bite to the sound’s attack, similar to a fingernail or a plectrum gliding on a string.

External Audio ⚓︎

While the Pulse and Noise modes can serve as a starting point for a wide range of physical modeling sound design, they are still quite limited compared to the standalone Pulse and Noise modules. You may also wish to experiment with triggering the physical models with different kinds of audio sources.

The Ext Audio input will take any audio signal and mix it with the pulse or noise generated by the Exciter. The amounts of pulse/noise and external audio in the mix can be controlled with the volume knobs to the right of the Trig/Env and Ext Audio input jacks.

Be careful with the frequency content of the external audio signal. If there is a correlation with the harmonic content of the physical model, there is a risk of the physical model sounding unnaturally loud at the resonant frequencies. Try to use wide-band sources like noise or short pulses, or keep the decay parameter of the physical model very low to reduce resonance.

In Depth ⚓︎

Filtering ⚓︎

The Freq and Color knobs control a low-pass and a high-pass filter in series that shape the pulse or the noise depending on the current mode.

The filters do not affect the external audio input signal (Ext Audio).

Filter Frequency

The Freq knob directly controls the cutoff frequency of the low-pass filter and can also indirectly control the cutoff frequency of the high-pass filter when the Color knob is in its lower half.

If you want the Exciter filter’s cutoff frequency to follow the pitch of the physical model, use the Freq Mod knob: at 0% the filter frequency will be fixed, and at 100% it will perfectly follow the pitch.

Filter Color

The Color knob controls both the resonance (Q factor) of the low-pass filter and the cutoff frequency of the high-pass filter in relation to the low-pass filter.

• At 0% (centered), the low-pass filter has zero resonance and the high-pass filter’s cutoff frequency is 8 octaves below the low-pass filter.

• From 0% to -100% (turning the knob counterclockwise from the center), the cutoff frequency of the high-pass filter increases until it reaches the cutoff frequency of the low-pass filter. The low-pass filter resonance doesn’t change.

• From 0% to 100%, the low-pass filter resonance increases, while the high-pass filter remains 8 octaves below the low-pass filter.

By introducing a high-pass filter, the first half of the Color knob can be used to reduce the prevalence of low frequencies in the sound produced by the physical model. This can reduce muddiness and boominess.

In Noise mode, the second half of the Color knob can be used to create resonant filter sweep effects if the Freq knob is modulated by an envelope or an LFO. In Pulse mode, it can add a wooden or metallic quality to the pulse depending on the cutoff frequency of the low-pass filter and the amount of resonance added by the color parameter. In both modes, it can be used as a tone-shaping tool to emphasize the harmonics of the physical model around the filter’s cutoff frequency.

Velocity ⚓︎

Connect the Keyboard Vel output or any other bipolar signal ranging from -5V and 5V to the Exciter Vel input to control the volume of the sounds produced by the Objeq Oscillator or the Tube Oscillator.

See Understanding Signals—Velocity for more information on how velocity works in Multiphonics.