OMF-1
Analog filter Rack
Overview of the OMF-1
The complete filter rack module contains:
A four pole true analogue filter. This is based on the famous transistor ladder filter
developed by Dr Bob Moog in the 1960s. A front panel pot controls the filter cut-off
frequency, another controls the resonance. The resonance control is configured not to
cause volume drop when turned up. The filter can be made to oscillate if required.
Two filter outputs are available. One is the Fizz output. This is a type of -6dB/octave filter
and it gives a unique filtering effect with a real bite. The other is the Smooth output. This is a
classic -24dB/octave filter, and gives a smooth
warm analogue filter sound. Each output
goes via its own reversible attenuator. This means not only can you adjust the output level,
but also the phase of the output signal. This allows complex filter types to be made when
the two outputs are mixed together in various degrees.
A wide range single ended pre-amplifier is included. You can use the OMF-1 with virtually
any input from guitars to synthesisers. A peak indicator will allow you to monitor overloads,
although the OMF-1 is designed to overdrive beautifully.
An inbuilt low frequency oscillator with triangle and square waveforms. The frequency can
be changed from 0.2Hz to over 40Hz. A LED gives visual indication of the speed of the LFO.
Use this to create auto wah, vibrato and phaser type effects.
An ingenious dynamic envelope section that can move the filter cut off point up or down
automatically. It can be put into one of three modes at a flick of a switch:
FLR
It can function as a useful envelope follower, with controllable attack and decay
times. Perfect for simulating many classic dynamic follower filter boxes. Play louder
and hear the filter open up.
AR
It can be a standard attack-release envelope generator. This is triggered either by
the LFO, external gate signal or by an automatic audio trigger circuit with a
variable threshold level. Powerful for creating rising crescendos.
AD
It can be a standard attack-decay envelope generator. This is a type of one shot
envelope, that rises and falls at the presence of an initial trigger signal. Useful for
percussive type sounds.
The output level can be controlled with a master volume control. The output circuitry is
configured to drive long length cables with ease and offers a ground compensating facility to
reduce the likelihood of ground loops.
A side chain input is available. This is a second audio input that can control the main input,
but is not heard directly. Use this to trigger the envelope generator, or drive the envelope
follower. A common use of this is to make the main audio program respond to a drum
machine's output for syncopated effects. Use a deep rich string patch as your main input,
and listen to the drum machine automatically pulse the output to the beat.
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