VM Rackmode String Filter processors

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The Cherry Audio VM Rackmode String Filter comprises 36 high-Q parallel bandpass filters arrayed throughout the musical range (say that five times fast... go ahead, we'll wait). The original unit was intended to mimic the multiple static resonances of a stringed instrument body such as the violin or cello. When simple waveforms (especially solo waveforms) are played through it, the String Filter imparts a woody richness to the sound making it sound more "stringlistic."

Having so many resonant filters close together has a secondary effect on the amplitude of moving harmonics as well. If vibrato is applied (i.e., frequency modulation), some harmonics will ride up and down their nearby filter slopes creating amplitude modulation of that harmonic. It is this kind of detail that the unit was created for, but it can create interesting effects from many signal sources.

The adjustment of this mix has a profound effect on the resulting tone. The filters are arranged into odd and even interleaving sets which are associated with the left and right stereo outputs. The stark stereo spread of the odd/even splitting can be lessened by setting the Width control more toward Mono. Note that the String Filter is really useful for stereoizing mono sources!

Input jacks- Plug incoming signals in here. The signal(s) will be routed to filters differently depending upon left and right input routing as follows:

  • L (mono) in - L and R out results in the L audio going through all filters coming out in odd/even stereo.

  • L and R input and outputs- L audio goes through odd and R audio goes through even filters coming out in stereo.

  • L (mono) in, L and R out- L audio goes through all filters coming out in odd/even stereo. (This is great for stereoizing a mono signal.)

  • L (mono) and L (mono) out- L audio goes through all filters and outputs all filters in mono. The individual outputs are monauralized versions of the filter groups.

Frequency and Resonance Offset and Mod

Frequency Mod jack and attenuator- Allows positive or negative CV mod of the Frequency Offset control (see below).

Frequency Offset- The filter frequencies of the original unit were fixed, but we've added a Frequency Offset knob that simultaneously adjusts the frequencies of all 36 filters in parallel.

Resonance Mod jack and attenuator- Allows positive or negative CV mod of the Frequency Offset control (see below).

Resonance Offset- Globally adjusts the bandwidth of all 36 filters. Turning this down all the way pretty much renders the effect inaudible (not at all stringy), and turning it up all the way will sound clangy and metallic.

Frequency Group Controls

Lo/Lo-Mid/Hi-Mid/Hi filter levels- The 36 filters are divided into four groups of nine: Lo, Lo-Mid, Hi-Mid, and Hi. The four groups are mixed via their respective level controls. The adjustment of this mix has a profound effect on the resulting tone.

Frequency Band mod jacks and attenuators- Allows positive or negative CV mod of each frequency group control.

Individual Frequency Group Outputs

Each of the four frequency groups has an individual out. These can be routed for further individual processing.

Output Section

Width- Sets the stereo panning width of the filters.

Output jacks and meters- The output signal(s) of the String Filter. The stereo output meters display nominal level, you know the drill here!