Make Noise DPO - Manual (Page 9)

VCO B core behavior
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 inte-
ger frequency of the applied external VCO, VCO B will reset to match the external VCO, and thus small
tuning errors will be corrected. eXternal LOCK is useful for cleaning up FM and audio rate modulation and
will 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 remained locked, there will be 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 IN) 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 KB controller to the VCO B 1V/ Octave input and set the FOLLOW control to
100% VCO A will follow the pitch tracking of VCO B. As FOLLOW is decreased from 100% VCO A will lag
further and further behind VCO B to the point of not actually following. At 0% FOLLOW, VCO A is indepen-
dent of VCO B. If you patch into the Follow CV IN, then the associated potentiometer becomes an attenua-
tor 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 100% will introduce 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 you will see this LED flash more slowly. This LED is also useful for visual indication of
the rate of the LFO when VCO A is programmed for LFO operation.