User manual

22
Filter
Sequential
Filter
The function of the lter is to subtract frequencies from the sound
produced by the oscillators and noise generator, thereby changing the
overall harmonic content of the synth’s sound. This change is varied over
time using the Filter Envelope to produce more dynamic timbres.
The original Prophet-5 had three incarnations: the Rev1, Rev2, and Rev3,
each with their own unique characteristics. Probably the most signicant
difference between the Rev 1/2 and the Rev3 was that they had different
lters, which gave the instruments a different sound character. The Rev
1/2 had a Dave Rossum-designed 2040 low-pass lter, while the Rev3
had a Doug Curtis-designed CEM 3320 low-pass lter.
The new Prophet-5 and Prophet 10 provide the best of all worlds by
providing both types of lters. You can select between these with the rev
switch. Each has its own unique character:
• rev 1/2 is a Dave Rossum-designed SSI 2140 lter. Its 4-pole, 24
dB-per-octave resonant design is functionally identical the 2040 lter
found on the original Sequential Circuits Prophet-5 Rev1 and Rev2. It
can self-oscillate when resonance is set to its maximum.
• rev 3 is a genuine Doug Curtis-designed CEM 3320 lter. Its 4-pole, 24
dB-per-octave resonant design is functionally identical the lter found
on the Sequential Circuits Prophet-5 Rev3. It can self-oscillate when
resonance is set to its maximum.
The differences between these lters can be subtle or pronounced, depend-
ing on their individual settings, the amount of lter resonance applied,
and other factors.
The rev switch not only changes lter type, but also the Filter Envelope’s shape/
response to match the original Prophet Rev 1/2 and Rev 3 respectively. After setting
the Filter Envelope as desired, try changing lter type to hear the difference.