APPLIED ACOUSTICS SYSTEMS STRINGSTUDIO Manual do Utilizador descarregar pdf (Página 47)

4.3 The FX View 47

4.3.8 Wah

The Multi-Effect module includes 2 different types of Wah effects: wah wah, and auto wah. These

effects are used to enhance a frequency band around a varying center frequency using a bandpass

ﬁlter. In the wah wah effect, the center frequency of the bandpass ﬁlter varies at a rate ﬁxed by

the user. In the case of the auto-wah, the variations of the center frequency is controlled by the

amplitude envelope of the incoming signal.

The Freq knob is used to control the central frequency of the ﬁlter. Turning this knob clockwise

increases the center frequency. In the case of the Wah Wah effect, the center frequency oscillates

around the value ﬁxed by the Freq knob while with the Auto Wah effect, the setting of the Freq

parameter ﬁxes the starting point value of the varying center frequency.

The Depth knob controls the excursion of the center frequency of the ﬁlter. In the case of

the Wah Wah effect, this excursion is applied around the value ﬁxed by the Freq knob while in

Auto Wah effect the value of the center frequency increases from the value ﬁxed by the Freq knob.

Turning this knob clockwise increases the excursion of the center frequency. Note that the Depth

parameter is also adjustable from the Play view.

Finally, the Rate knob controls the frequency or rate of the modulation of the center frequency

of the ﬁlter. In the case of the Wah Wah effect, turning this knob clockwise increases the rate of

the modulation. In the case of the Auto Wah ﬁlter, this knob is labeled Speed and controls the time

constant of the envelope follower. Turning this knob clockwise decreases the time constant, or in

other words the reaction time, of the envelope follower.

4.3.9 Notch Filter

The Notch Filter does

essentially the opposite of

a band-pass ﬁlter. It at-

tenuates the frequencies in

a band located around the center frequency and leaves those outside of this band unchanged as

shown in Figure 30. As was the case for the Wah Wah effect, the ﬁlter can be modulated.

The Freq knobs is used to control the central frequency of the ﬁlter. Turning this knob clock-

wise increases the center frequency. The Depth knob controls the excursion of the center frequency

of the ﬁlter around its center frequency. Turning this knob clockwise increases the excursion of the

center frequency. Finally, the Rate knob controls the frequency or rate of the modulation of the

center frequency of the ﬁlter. Turning this knob clockwise increases the rate of the modulation.

Note that the Depth parameter is also adjustable from the Play view.

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APPLIED ACOUSTICS SYSTEMS STRINGSTUDIO Manual do Utilizador Página 47