TRAX RetroWave Owner’s Manual
< 12 >
Filter Free-for-All
Next, we come to one of the most important modules in the R-1, the
Voltage Controlled Filter (VCF).
The filter works best with square, reverse sawtooth and triangle waveforms; sine waves, having no
harmonics, will come out of the filter in much the same way as they went in!
At the moment, the filter is set to pass all frequencies without attenuation. The
RESONANCE
control
should be at halfway position; if you now turn the
FREQUENCY
control to and fro, you will hear the
familiar synthesizer “wah” effect, which characterises the instrument and makes it so unique. As you turn
the FREQUENCY control down towards zero, the sharp edges of the square wave signal are “rounded
off” as the filter removes the top range of frequencies. Turning this control fully anti-clockwise will fade
out the signal completely, as the audio frequencies are filtered out entirely.
Got “Auto Wah” if You Want It
You can achieve a periodic, automatic “wah” effect, by turning up the
VCF – MODULATION SOURCES
– LFO 2
control, which will modulate the cut-off frequency of the filter automatically. Adjust LFO 2’s
FREQUENCY control to alter the rate of “wahs”.
Turning the RESONANCE control further clockwise will make the sound “juicier”, and eventually a point
will be reached where the filter oscillates, producing a roughly sinusoidal waveform that can be played
like a VCO – more details can be found in the Voltage-Controlled Filter section later.
Turning RESONANCE down towards minimum will make the sound subjectively louder and more
“boomy”. This setting has many uses, especially where a sound needs to have plenty of body and
substance, such as a killer bass line.
Noisy Noodling
In addition to the VCO, there is another signal source available - white noise. Turn down the VCO, SUB I
and SUB II level controls to zero, turn down the VCF – MODULATION SOURCES – LFO 2 control to
zero, and advance the NOISE control; you will hear a distinctive “hissing” sound. This noise is useful for
adding breath effects to flute sounds, creating surf and rain effects or similar, and can be the basis of
explosive sounds such as gunshots, snare drums etc. when used with the ADSR.
Random Musings
To get a random modulation of the VCF cut-off frequency, you an also apply the same random voltage
signal we sent to the VCO earlier, by turning the
VCF – MODULATION SOURCES – SAMPLE & HOLD
control clockwise. Keep the filter RESONANCE control near oscillation setting to get the best effect.
Envelopes and Such
OK, so what next? Our basic sound now needs some shaping, to give each note played a distinctive
character of its own. The way we do this is to set up an
envelope
for the sound using the
ADSR/VCA
module.
This comprises the
ADSR
(
Attack – Decay - Sustain – Release
) circuit and a
Voltage-Controlled
Amplifier
(VCA).
The ADSR sends a one-shot control waveform to the VCA each time it receives a gate
signal, thus controlling the contour of the final sound that is sent to the external amplifier.
