Future Retro XS - Manual (Page 31)

ANALOG CONTROLS
The WAV B setting routes Oscillator B’s waveform, determined by the WAVE B control setting, to
modulate the filter’s cutoff frequency. Use this to create direct FM modulations when Oscillator B is in
its audio range, or to create slower sweeping effects when Oscillator B is producing frequencies below
the audio range. Note that all of Oscillator B’s waveforms range from –5 to +5 volts, causing the filter’s
frequency to rise above and fall below the filter frequency set by the filter’s cutoff control.
The B ENV setting lets Envelope 1 control the amplitude of Oscillator B’s waveform, determined by the
WAVE B control setting, to modulate the filter’s cutoff frequency. This provides a more complex form
of FM where the modulation source varies it’s amplitude over time.
The WAV C setting routes the waveform selected with the WAVE C control to modulate the filter’s
cutoff frequency. This allows you to modulate the filter’s cutoff frequency with any of the sub
oscillators, the ring modulator, the white noise source, or any external audio which is inserted into the
AUDIO IN jack.
Note that the ring modulator and the white noise source waveforms range from –5 to +5 volts, causing
the filter’s frequency to rise above and fall below the filter frequency set by the filter’s cutoff control,
while all three sub oscillator waveforms have a 0 to +15 volt range. When the sub oscillators are
selected for WAVE C and are modulating the filter’s cutoff frequency, the filter frequency will become
higher than that set with the filter’s cutoff control.
ENV 1 -/+: The ENV 1 control sets the amount of sweep that Envelope 1 will have on the filter’s cutoff
frequency. This control provides both positive and negative polarity envelope shapes to sweep the
filter’s frequency. With this control set to it middle position, Envelope 1 will have no effect on the
filter’s frequency. When this control is rotated counter-clockwise of the middle position negative
polarity envelope sweeps will occur. When this control is rotated clockwise of the middle position,
positive polarity envelope sweeps will occur. Since both positive and negative polarity envelope shapes
have a range of 0 to +10 volts, this will cause the filter’s frequency to always rise above the normal
frequency set with the filter’s cutoff control. This keeps both envelope polarities within the same usable
range to eliminate unnecessary adjustments of the filter’s cutoff frequency as is typical with most
synthesizers.
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