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CHAPTER 

 

4

 

Introduction

 

 

 

the high pass filter which 

works in the opposite manner of 
the low pass filter: It suppresses 
the lower frequencies in a signal 
and lets the higher frequencies 
pass.

 

 

 

the band pass filter which 

suppresses both ends of the tonal 
spectrum and allows only a nar-
rowly defined bandwidth of the 
original sound to pass.

 

 

 

The band stop filter, band 

reject filter or notch filter which 
works in the opposite manner of 
the bandpass filter. It allows all of 
the frequencies of a signal except 
for a narrow frequency band 
around the cutoff to pass. The 
term “notch” is fairly descriptive; 
you might say this filter chops a 
notch out of the sound  spectrum.

Now activate the different operat-
ing modes and rotate the 

 

 

pot to get a feel for the way each 
filtering option works.

Along with the 

 

 pot, the 

 

 pot is the most impor-

tant control feature of a filter. The 
filter resonance increases the vol-
ume of the frequencies located 
near the cutoff frequencies and 
suppresses the more remote fre-
quencies. This sound shaping fea-
ture has a striking effect - 
especially when used in conjunc-
tion with the low pass filter: it pro-
duces a nasal or honking type of 
tone which increases as you turn 
the resonance up. Experiment by 
varying the 

 setting in 

the different operating modes in 
conjunction with different CUTOFF 
settings. You will find the effect 
that the RESONANCE pot achieves 
is markedly different for the band 
stop filter in comparison to the 
effect it has on the other filter 
types: as the resonance increases, 
the bandwidth of the notch 
decreases; in other words more 
frequencies on both sides of the 
filter frequency are allowed to 
pass.