Switches the Filter between the two classic filters that the Prophet~5 utilised during its production. The envelope shapes of both the filter and amplifier also change.
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The primary sonic difference between the filters on the Prophet-5 Rev 1/2 and Rev 3 stems from the filter chips used: The Rev 1 & 2 Prophet-5 used the SSM2040 (designed by Dave Rossum), while the Rev 3 switched to the CEM3320 (designed by Doug Curtis).
The SSM2040 delivers a rich, organic, dark, and slightly gritty character with a more musical, fuzzy resonance and a warmer, yet more aggressive and unrefined tone that’s often likened to a Moog-style ladder filter on a chip.
In contrast, the CEM3320 in the Rev 3 is cleaner, more precise, and stable, generally sounding brighter or "thinner" to some ears, with a more abrupt high-frequency roll-off due to its logarithmic envelope response compared to the more linear behaviour of the SSM.
Many claim the Rev 1/2 filter often feels more characterful (with subtle instability). However, in our experience it is less reliable that the Rev 3 filter, which became the defining "80s Prophet sound"
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This control determines the initial cut-off frequency of the filter. From 10Hz to 8800Hz for Rev 1/2, and 25Hz to 8400Hz for Rev 3.
This control determines the amount of resonance (”Q” or “emphasis”) of the filter. Note that the filter resonance characteristics change dramatically depending on the Filter Type Selected.
Traditionally on analogue filters increasing the resonance was accompanied by a decrease in bass response. The Q-Compensation parameter reintroduces that lost bass with 7 discrete steps. Ranging from 1 (least compensation) to 7 (most). This feature is modelled from the Rev4 hardware, where it was introduced in a firmware update.
This control determines the amount of filter envelope that modulates the filter.
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You may notice that it’s possible to modulate the filter using the filter envelope twice, once here, and once via the poly-mod section. These signals combine and amplify each other, essentially increasing the available depth range.
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This knob determines the amount of Filter Tracking going into each voice. It can be adjusted to the desired discrete filter tracking value from 0% to 100%. When set to “100%”, it causes the filter in each voice to “track” the keyboard.
This control determines the initial rise time of the filter envelope. The shortest time is selected by setting it fully counter-clockwise. From 0ms to 30s.
This control determines the fall time of the filter envelope down to the level set by the sustain control while a key on the keyboard is being held down. From 0ms to 28s.