Moog Music Voyager Old School - Manual (Page 18)

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Voyager OS User’s Manual - The Components
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Voyager OS User’s Manual - The Components
Filter Section Controls:
Cutoff:
The CUTOFF knob is the main fi lter control. This sets the cutoff frequency of both fi lters in Dual Lowpass
and Highpass/Lowpass mode.
In Dual Lowpass mode, the frequencies to the right of the indicator on the knob are the frequencies that
are fi ltered out. The frequencies to the left of the indicator are the frequencies that are allowed to pass
through the fi lter. This is why as you turn the control clockwise the cutoff frequency becomes higher and
the sound becomes brighter. Of course, to hear the effect of a lowpass fi lter it helps to have a signal rich
in harmonics which provides high frequencies to fi lter. A good example of a sound rich in harmonics is a
sawtooth waveform.
In Highpass/Lowpass mode, the combination of highpass and lowpass fi lters forms a bandpass fi lter. In this
mode, the CUTOFF control changes the center frequency of the passband.
Spacing:
The SPACING control is used to determine the difference between the cutoff frequencies of the two fi lters
in both Dual Lowpass mode and Highpass/Lowpass mode. The numbers on the legend around the control
knob refer to octaves. When the SPACING control knob is centered, the cutoff frequencies of the two
fi lters are identical and the fi lter sounds like a classic Moog Filter. Setting the SPACING control to +1 in
Dual Lowpass mode means that the right fi lter has a cutoff frequency equal to where the CUTOFF control
knob is set, and the left frequency has a cutoff frequency that is one octave higher than the right fi lter. This
means when the CUTOFF control is swept, two resonant peaks are heard, giving the fi lter a unique quality.
In Highpass/Lowpass mode, the SPACING control sets the difference between the cutoff frequencies by
shifting the Highpass fi lter cutoff frequency up or down. When the SPACING control is fully clockwise, the
cutoff frequencies of the two fi lters are the same, making for a very narrow bandpass fi lter.
Resonance:
The RESONANCE control causes feedback in the fi lter circuit that adds harmonic emphasis at the cutoff
frequency. This control affects the Lowpass fi lter(s) in either fi lter mode, but not the Highpass fi lter. When
the RESONANCE control is all the way down, the lowpass fi lters act as a tone control, rolling off the high
end (treble) as the CUTOFF control is turned down. As the resonance increases, the fi lter begins to form
a peak at the cutoff frequency. These peaks reinforce the harmonics of the signal being fi ltered, creating an
effect that can be described as vocal, nasal, or (at high resonances) zappy. As the RESONANCE control is
turned up the peak increases in strength until the control is set to about 8 or higher, where it begins to self-
oscillate, creating sine waves with the same frequency as the cutoff frequency.
Keyboard Control Amount:
The KEYBOARD CONTROL AMOUNT knob allows the fi lter cutoff to follow the key played on the
Voyager keyboard. A higher key will cause a higher cutoff frequency. This allows a sound to retain its
brightness as it is played higher on the keyboard.
Mode:
The fi lter MODE switch selects either the Dual Lowpass confi guration (DUAL LP) or the Highpass/Lowpass
confi guration (HP/LP).