Make Noise DPO Manual - page 10
10
There is one way to affect the behavior of the VCO B core. The External Lock input allows for an extremely weak, phase reversed
synchronization of VCO B to an external VCO where as VCO B approaches an integer frequency of the applied external VCO, VCO
B resets to match the external VCO and small tuning errors are corrected. External Lock is useful for cleaning up FM and audio rate
modulation and does not impart much change in the timbre or introduce strong harmonics to VCO B. It is useful for chaining
together multiple DPOs (or DPO and other VCO) for more complex FM, chords and other patches where tuning errors need to be
minimized.
Because External Lock input is phase-reversed, it is also possible to achieve very interesting amplitude modulations by summing
VCO B along with a signal from the VCO supplying the External Lock input. Because their phase is reversed, as long at the VCO
cores remains locked, there are varying degrees of cancellation between the two VCOs, depending upon the wave shapes and
levels programmed at the summing stage. By modulating VCO B frequency (through Expo CV Input), it is possible to knock VCO B
out of External Lock and thus, amplitude is regained.
The External Lock input expects a 10Vpp square or pulse shaped signal; however, just about any signal could be used with
varying degrees of success. The Duty Cycle (width) and Amplitude (height) of the signal will have some affect on the outcome.
FOLLOW
If you patch a sequencer or keyboard controller to the VCO B 1V/Octave input and set the Follow control to full clockwise, VCO A
follows the pitch tracking of VCO B. As Follow is decreased from full clockwise, VCO A lags further and further behind VCO B to
the point of not actually following. At full counter clockwise Follow, VCO A is independent of VCO B. If you patch into the Follow
CV Input, then the associated potentiometer becomes an attenuator for the incoming CV (as on the Optomix CV ins), allowing for
external control over how VCO A follows VCO B.
Follow is useful in maintaining FM or Sync Ratios while controlling the DPO with a sequencer or keyboard. The lag that occurs
when Follow is set to less than full clockwise introduces moments of dissonance and noise due to the temporary tracking errors.
This is a wonderful way to introduce uncertainty to an otherwise stable sequence of notes.
Beat Frequency LED
This LED gives visual indication of phase difference between VCO A and B. It is useful for fine tuning simple oscillator frequency
relationships such as unison, octaves and fifths. As the two oscillators approach these musical relationships, the LED flashes more
slowly. This LED is also useful for visual indication of the rate of the LFO when VCO A is programmed for LFO operation.
VCO B Core Behavior