SHIFT waveshaper
Block diagram
This simple circuit combines two mixers and a comparator to form a wave-shifter that, at
first glance, doesn’t look like much – however it
packs a lot of shaping capabilities
such as
sawtooth frequency-doubling
, complex waveshaping,
distortion
, self-oscillation and more,
especially using feedback
patching techniques as we’ll see later.
Basically, both and get summed together and then fed to both the
comparator and the second summer, while the fixed -1.8V reference voltage cancels out
the offset introduced by the comparator.
To better explain how SHIFT works, we’ll assume that the input of the circuit it’s a 10Vpp
sine wave. If it
e600mV,
the comparator’s output will change and
subtract 8V
to
the signal seen at the SHIFT output, introducing a sharp discontinuity/fold to the
waveform. The sine wave will then continue its cycle unaffected; when it
drops below
+600mV
the comparator’s output will change again,
adding 8V
to the signal seen at the
SHIFT output, producing another discontinuity in the waveform.
The SHIFT circuit’s behavior is roughly pictured by the symbol next to its output: the
straight line represents
0V
, and the altered sawtooth wave portrays the
resulting
waveform
of the following base patch:
SIGNOS
- User Manual | Page 11
OUT
+
COMPARATOR
-1.8V
+
(main input)
0 V
+6 V
-6 V
0 V
+5 V
-5 V
Fully open VCA
INPUT
(sine wave, 10 Vpp)
SHIFT OUTPUT
(altered sine wave, 12 Vpp)
+600mV
-8V
+8V
