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25 | The Voltage Controlled Filter (VCF)

RESONANCE

Also known as Emphasis, or Q, RESONANCE takes a portion of the Filter

output and channels it back to the input of the Filter. This creates a

resonant peak, or boost, that occurs at the Cuto frequency. Rotating the

RESONANCE knob clockwise will increase this resonant peak; rotating the

knob counterclockwise will decrease the amount of this resonant peak.

At maximum Resonance settings, the VCF can become self-oscillating. As

modulation is applied to the Cuto frequency, the relationship between

Cuto and Resonance can be heard with more clarity.

FILTER MODULATION PARAMETERS

As with Oscillator Modulation, Mavis contains two modulation sources that can be applied to vary the

Cuto frequency of the Filter. The ﬁrst is the LFO (Low Frequency Oscillator). This provides a repeating,

cyclic change based on the current settings of the LFO RATE and LFO WAVE parameters. The second is

the EG (Envelope Generator). This creates a one-shot, continuously changing control signal based on the

current settings of the ATTACK, DECAY, SUSTAIN, and RELEASE knobs. In this case, EG modulation can

be used to add articulation to each note as it is played, or to create other dramatic modulation sweeps.

This EG control signal begins anew each time a key is pressed or an external Gate is received.

VCF MOD MIX (Voltage Controlled Filter Modulation Mix)

Mavis allows both modulation sources to be applied to the value of the

Cuto frequency parameter simultaneously. The VCF MOD MIX knob sets the

balance between the two modulation sources (LFO and EG). Rotating this

knob fully counterclockwise will select only the EG as the modulation source.

Rotating this knob fully clockwise will select only the LFO as the modulation

source. In between those two extremes, the VCF MOD MIX knob acts as a

balance control, or crossfader, between these two modulation sources.

VCF MOD AMT (Voltage Controlled Filter Modulation Amount)

This knob determines the amount of modulation being applied to the Cuto

frequency. Unlike any of the other Mavis knobs, this control is bi-polar. In

the center position, no modulation is being applied; the modulation amount

is zero. Turning the knob clockwise from the zero point will add more and

more modulation to the Cuto frequency parameter. Turning this knob

counterclockwise from the zero point will still add more and more modulation

to the value of Cuto frequency parameter, however, this modulation will

have an inverse value. For example, instead of the EG ATTACK parameter

raising the Cuto frequency over time, as with a positive VCF MOD AMT

value, the EG ATTACK parameter would instead lower the Cuto frequency

over time when a negative VCF MOD AMT value is chosen.

Moog MAVIS User Manual

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