5. Parameter Reference
5.4. FILTER
A filter is a crucial part of a synthesizer. The Exciton's filter allows you to create the wide variety of sounds.
5.4.1. ON
Enables/disables a filter.
Setting the switch on, mixer output is sent to the filter. The signal is modulated in the filter and sent to the amplifier.
Setting the switch off, mixer output is sent to the amplifier directly. The filter is bypassed in the circuit and has no effect at all.
5.4.2. Type
Sets the filter type and its slope.
(1) Type
Sets the filter type.
Lowpass filter(LP), highpass filter(HP), band pass filter(BP) and band reject filter(BR) are available.
(2) Slope
Sets the filter slope.
Four slope types (6/12/18/24[dB/Oct]) are available for lowpass/highpass filters. Two slopes(12[6+6]/24[12+12]) are available for band pass/reject filters.
Each filters have the following properties.
Lowpass filters eliminate frequency elements above the cutoff frequency. The slope goes steeper with the numbers (6 to 24).
Highpass filters eliminate frequency elements below the cutoff frequency. The slope goes steeper with the numbers (6 to 24).
Band pass filters eliminate frequency elements outside the cutoff frequency. The slope goes steeper with the numbers (12 to 24).
Band reject filters eliminate frequency elements around the cutoff frequency. The slope goes steeper with the numbers (12 to 24).
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| Lowpass filter | Highpass filter | |
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| Band pass filter | Band reject filter |
5.4.3. Saturation
Sets the saturation of a filter.
(1) Saturation Level
Sets the saturation level.
(2) Saturation Curve
Sets the saturation curve.
The saturation function limits the output signal in a certain range. It simulates the property of an analog circuit. The parameters are as follows.
Saturation level sets the upper and lower limit of the output signal.
Saturation curve specifies the limitation curve. "hard" has a property like high-performance transistors or op-amps. "soft" has a property like old vacuum tubes. "mid" is the middle of "hard" and "soft".
Using the saturation, the output is limited and distorted. If you do not emphasize the resonance, it is only used for limiting the output for safety. But emphasizing the resonance, the filter oscillation is controlled with both saturation curve and level. Setting the saturation level low or setting the type to soft suppresses the filter oscillation. You can also use the saturation for distorting sounds with setting the saturation level low.
5.4.4. Frequency
Sets the cutoff frequency.
5.4.5. Resonance
Sets the resonance. It has no effect for 6dB/Oct lowpass/highpass filters.
Resonance changes the filter property by resonating the input signal in the filter. The properties of the lowpass filters and the highpass filters with resonance are shown below (6dB filters does not have a resonance setting because they cannot resonate).
Emphasizing the resonance, frequency components around the cutoff frequency are boosted. Sounds using resonance emphasis are popular for analog synthesizers.
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| Lowpass filter | Highpass filter | |
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| Band pass filter | Band reject filter |
Emphasizing the resonance, the filter oscillates by itself and the output is boosted. You ought to care for for the large output. Especially, tweeter units of monitor speakers are weak for continuous oscillation inputs. If you uses an expensive monitor speakers, you should take care for continuous oscillation inputs, especially for high tones (and please take care for your ears also!).
Exciton takes special care for avoiding unusual output. For lowpass filters, the signal is always guarded by the saturator. For highpass filters, the resonance range is limited to avoid the too much self oscillation. But please do not forget that speakers are not so strong, especially for large continuous inputs.
Utilizing the filter resonance, you can play sounds with the filter. It is a common technique for analog synthesizers and typically used for percussion sounds.
When you use the filter oscillation, please input a little signal (usually a small noise) to the filter. For (real) analog synthesizers, a few noise is generated inside the circuit and the filter can oscillate by it self using the noise. But the Exciton's filter is very clear and does not generate a noise. Adding a slight noise to the Exciton's filter, the filter can oscillate with the resonance.
5.4.6. Key Follow
Specifies the key follow ratio of the cutoff frequency versus MIDI note-on messages.
Key follow ratio can be set from 0% to 200%. 100% sets the frequency scale to the same as normal keyboards (a semitone). 200% comes to the whole tone (2 semitones) and 50% to the quatertone. Setting to 0% comes to the same frequency for all note-on messages.
5.4.7. Modulation Source/Destination A/B
Specifies modulation source/destination configurations.
The filter section has two modulation slots (A/B). Exciton has 4 modulation sources (2 envelopes and 2 LFO's) and two of them can be selected and assigned to the cutoff frequency. They can be also assigned to the resonance (do nothing for 6dB/Oct filters).
(1) Source
Specifies a modulation source. It can be selected from ENV1, ENV2, LFO1 and LFO2.
(2) Destination
Specifies the modulation destinations.
Clicking FREQ button on, the modulation is added to the cutoff frequency. Clicking RES button on, the modulation is added to the resonance (no effect for 6dB/Oct filters). Both switches can be set to on at the same time.
5.4.8. Modulation Depth A/B
Sets the modulation depth.
The depth can be set to both positive and negative directions. If you assign a envelope to the cutoff frequency, setting to the positive becomes the frequency up and the negative becomes the frequency down.
The knob scale for the modulation depth is quadratic (same as oscillators). See 3.2.7. Modulation Depth A/B for detail.
If you want to set a large modulation and 100% is not enough, you can specify the same setting for both modulation A and B. It makes the modulation twice bigger than one. Also, you can use assignable modulation for routing additional modulations and controls.
5.4.9. Modulation Velocity Sens. A/B
Sets the MIDI note on velocity sensibility with the modulation depth.
Setting the sensitivity to 100%, the depth varies from 0 to 200% with the note on velocity. Setting to 0% makes the constant for all velocities.
You can use the velocity sensitivity for the modulations and add expressions to the sounds. For example, assigning an envelope to the cutoff frequency and changing the frequency with the note on velocity is a common technique for making sounds.
