User`s manual

Description of controls is as follows:

Cutoff Specifies frequency in Hertz below which all

Frequency: signals are attenuated. Frequencies above this cutoff are unaffected. Minimum

Cutoff Frequency is 100 Hz, while the maximum Cutoff Frequency is 5400 Hz.

Cutoff Frequency can be adjusted in 1 Hz steps.

Stopband Specifies amount in dB by which frequencies below

Attenuation: the Cutoff Frequency are ultimately attenuated. Stopband attenuation is adjustable

from 0dB to 90dB in 1 dB steps.

Transition Specifies slope at which frequencies below the

Slope: Cutoff Frequency are attenuated in dB per octave. Sharpest attenuation occurs

when Transition Slope is set to maximum, while gentlest attenuation occurs when

Transition Slope is set to minimum. Note that the indicated value changes

depending upon Cutoff Frequency.

A graphical description of the highpass filter and its controls is shown below.

Figure 7-5: Highpass Filter Graphical Description

7.4 Bandpass filter

Application:

The Bandpass filter is used to decrease the energy level (lower the volume) of all signal

frequencies below a specified Lower Cutoff Frequency and above a specified Upper Cutoff

Frequency, thus combining the functions of a seriesed Lowpass and Highpass filter into a single

filter. The signal region between the Lower Cutoff Frequency and the Upper Cutoff Frequency is

called the passband region. The Bandpass filter is useful for simultaneously reducing both low-

frequency rumble and high-frequency hiss.

The Lower Cutoff Frequency is usually set below the voice frequency range (somewhere below

300 Hz) so that the voice signal will not be disturbed. While listening to the filter output audio, the

Lower Cutoff Frequency, minimum of 0 Hz, can be incrementally increased until the quality of the

voice just begins to be affected, achieving maximum elimination of low-frequency noise.

The Upper Cutoff Frequency is usually set above the voice frequency range (somewhere above

3000 Hz) so that the voice signal will not be disturbed. While listening to the filter output audio,

the Upper Cutoff Frequency, minimum setting of 100Hz over the Lower Cutoff Frequency, can be

incrementally lowered until the quality of the voice just begins to be affected, achieving maximum

elimination of high-frequency noise.

The amount of volume reduction outside the passband region can further be controlled by

adjusting the Stopband Attenuation setting (maximum volume reduction is 90dB). The slope at

which the volume is reduced from normal (at each Cutoff Frequency) to the minimum volume

(specified by Stopband Attenuation) can also be controlled by adjusting the Transition Slope

setting.