VCF.MUS.2

Lesson Summary 

Recognize resonance within the transistor ladder filter and identify the harmonic property changes.

Vocabulary 

Low Pass Filter - A filter that passes low-frequency signals and attenuates (reduces the amplitude of) signals with frequencies higher than the cutoff frequency.

 

 

High Pass Filter - A filter that passes high-frequency signals and attenuates (reduces the amplitude of) signals with frequencies lower than the cutoff frequency.

 

 

Band Pass Filter  - A filter that passes frequencies within a certain range and attenuates (reduces the amplitude of) frequencies outside that range.

 

 

Bandwidth - The difference between upper and lower frequencies.

 

 

Cutoff Frequency - The boundary in a filter at which signal begins to be reduced.

 

 

Q Factor - The amplitude and bandwidth of a filter at its cutoff frequency.  

Voltage Controlled Filter (VCF) - An audio filter that allows its cutoff frequency and resonance (Q) to be altered by an external control voltage. A VCF can act as a low-pass, high-pass,  or band-pass filter. 

 

Exercise 

Experiment with the VCF via the CUTOFF and RES knobs.

Set the Werkstatt to the settings in Figure 1.

 

Figure 1. VCF setting

 

We won't actually hear any sound from the Werkstatt until we start to turn the VCF CUTOFF knob clockwise.  What we are hearing is the cutoff frequency of the filter being swept through the frequency spectrum.  This changes the output of our Werkstatt in an interesting and musical way.  Now set the Werkstatt to the settings in Figure 2. 

 

 Figure 2. VCF RES Setting

 

Now when we sweep our CUTOFF frequency up and down we will hear a completely different sound.  This RES knob changes the resonance values in our filter and allowing us to create wild new sounds.  Experiment with both the CUTOFF and RES knobs to hear how they interact with each other. 

Materials 

Jumper Cables

 

 

 

 

Subject 
Unit