Pittsburgh Modular Microvolt 3900, Руководство пользователя

Страница: 26 / 70

26
11. Dynamic VCA
The dynamic VCA is the heart of the Microvolt 3900. An unique processing circuit that adds dimension to the
audio waveforms. The basic function of a VCA is to control the loudness of the sound over time. This includes
turning a sound on and off or subtly changing the output level.
The dynamic VCA is a modern interpretation of Don Buchla ’ s famous “ lopass ” gate. The lowpass gate circuit is
unique in the way that it simulates the characteristics of natural instruments. When used in lowpass gate mode
(19), louder sounds contain more harmonic content and quieter sounds contain less harmonic content. This is not
the case when using VCA mode(19). VCA mode simply changes the loudness of the sound without modifying the
harmonic content. There is no reason that synthesizers need to simulate how acoustic instruments function but
because of how it affects the harmonic content of sound, a lowpass gate sounds more organic or natural
compared to a standard VCA.
The original lowpass gate was limited to a static response time that varied from unit to unit. This made each
lowpass gate a little different. The dynamic VCA in the Microvolt 3900 adds a unique, dynamic response(21)
control circuit to the original Buchla lowpass gate concept allowing for customizable gate response times.
Dynamic VCA Patching Notes
•
The pluck button(22) bypasses the dynamics modulation trimmer(24) and creates a trigger from any sharp
signal sent into the dynamics modulation input(123). This triggers the dynamics response to create an
organic percussive strike. The pluck button works best in low pass gate mode(19) and the attack of the
envelope generator (41) is set to very short.
•
The input balance trimmer(23) is a mixer. The output of the filter is mixed with a signal patched into the
dynamic vca input(124). The input balance trimmer is bypassed if the dynamic vca input is not patched.
•
The dynamics slider(20) and dynamics modulation trimmer(24) work together to control the output level.
When using CV, the dynamics slider becomes the offset control and the dynamics modulation trimmer
controls the amount of CV manipulating the VCA level.