ABOUT ANALOGUE SYNTHESIS
FILTER -
tone
There are several different types of filter. These are Low Pass Filter, High Pass Filter & Band Pass Filter. The Low Pass Filter
allows harmonics below a set frequency to pass through the filter. Hence the name Low Pass Filter. The High Pass Filter allows
harmonics above a set frequency to pass through the filter. Hence the name High Pass Filter. The Band Pass Filter allows harmon-
ics at a set frequency to pass through the filter, the harmonics above & below the set frequency do not pass through the filter.
Hence the name Band Pass Filter. Below are the frequency response curves of the three types of filters.
Additionally the slope of the curve at which the filter rejects unwanted harmonics can be altered. The effect is similar to a “Q” con-
trol on a parametric EQ. In the 12dB position the Cutoff Frequency slope is less steep so the higher frequencies are not attenuated
as much as they are in the 24 or 18dB positions. This makes the resulting filtering in the 12dB position more subtle than the 24 or
18dB positions which you should select if you want the Cutoff Frequency to be more obvious. The slope is measured in dB per
Octave & below are the response curves of a Low Pass Filter with 24, 18 & 12 dB per Octave slopes.
All these filters have a Resonance parameter. This has the effect of emphasising harmonics at the cutoff frequency of the filter.
This is very useful for creating large tonal differences to a basic waveform. The effect is shown below as both frequency response
curves when resonance is applied in a the Filter.
Low Pass Filter with Resonance Responce Curves
Frequency
Volume
Cutoff
Frequency
Frequency
Volume
Cutoff
Frequency
Frequency
Volume
Cutoff
Frequency
No Resonance Mid Resonance High Resonance
Frequency
Volume
High Pass Filter with Resonance Responce Curves
Cutoff
Frequency
Frequency
Volume
Cutoff
Frequency
Frequency
Volume
Cutoff
Frequency
No Resonance Mid Resonance High Resonance
Frequency
Volume
Band Pass Filter with Resonance Responce Curves
Cutoff
Frequency
Frequency
Volume
Cutoff
Frequency
Frequency
Volume
Cutoff
Frequency
No Resonance
Mid Resonance
Frequency
Volume
12dB/oct LPF Responce Curve
Cutoff
Frequency
Frequency
Volume
18dB/oct LPF Responce Curve
Cutoff
Frequency
Frequency
Volume
24dB/oct LPF Responce Curve
Cutoff
Frequency
Frequency
Volume
Band Pass Filter Responce Curve
Cutoff
Frequency
Frequency
Volume
High Pass Filter Responce Curve
Cutoff
Frequency
Frequency
Volume
Low Pass Filter Responce Curve
Cutoff
Frequency
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