TRAX RetroWave Owner’s Manual
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subtle and interesting. It is really worth getting to know how it operates, as the number of sonic
possibilities is greatly increased, once you know how to dial in the required parameters.
The VCF is known as a low-pass filter, because it allows all frequencies below a certain “cut-off point” to
pass, filtering out all signals that are above it.
Starting on the extreme right of the module, we find two important controls:
FREQUENCY
This determines the cut-off point of the filter, and turning it clockwise allows more signal to
pass, the sound becoming brighter and louder. In addition to manual frequency control, the various
control voltages applied to the filter via the MODULATION SOURCES mixer can be combined, to
change the cut-off point automatically. This is a powerful feature, as it allows a multitude of control
voltages to be deployed simultaneously.
RESONANCE
Turning this control clockwise increases the emphasis on a narrow band of frequencies
near to the filter cutoff frequency – the higher the setting, the more fluid and “fruity” the sound becomes.
Advancing this control beyond the halfway setting will cause the filter to break into oscillation. This is
quite normal, and can be quite a useful feature.
The oscillation frequency can be altered via the FREQUENCY control, and can in fact be tuned to the
same pitch as the VCO (or set to some other musical interval), and the filter “played” along with it as an
additional oscillator. The pitch accuracy over the compass of a keyboard is not as good as that of the
VCO, but it is adequate for most musical applications.
Note that the oscillation level produced by the filter is much higher than that produced by the VCO, so
take care if using headphones.
Now let’s deal with the audio mixer. This combines the outputs of five signal sources: the VCO, SUB
OCTAVE I, SUB-OCTAVE II, NOISE and an external audio input (there is no level control for external
signals).
VCO
The selected VCO waveform is applied to a level control, for mixing with the other signals in any
proportion you wish.
SUB-OCTAVE I
is a 1:1 square wave signal, at exactly one octave below the VCO pitch, and available
continuously, no matter which VCO output waveform is selected. Sub-octaves are extremely useful for
fattening VCO tones, for rich bass sounds and organ-like effects. When combined with a VCO square
wave that is being slowly pulse-width modulated, the resulting fat sound belies the fact that the R-1 has
only one VCO.
SUB-OCTAVE II
is similar to SUB-OCTAVE I, but the square wave output is pitched at one octave below
SUB-OCTAVE I (two octaves below VCO pitch).
NOISE
This controls the level of white noise applied to the mix. You may recognise it as the hissing
sound heard when tuning between FM radio stations. It is a complex signal, containing all frequencies in
the audio spectrum in equal amounts.
In the field of electronics noise is normally something that is to be avoided at all cost, but in terms of
sound synthesis it is a very useful signal source that can be used in percussive effects, rain, thunder,
surf, whistle edge-noise, etc. when filtered and given a suitable envelope by the ADSR generator.
External audio signals can also be added to the mix, via the
AUDIO IN
jack. Note that this input is only
suitable for high-level sources, such as a CD or line output. Microphones will not work with this input,
unless boosted by a suitable preamplifier.
The external input is handy for allowing other instruments such as organs, electric pianos or other synths
