Audio Damage Dr. Device - Manual (Page 8)

1. Filter Controls
The FREQ controls the cutoff frequency of the filter. Rotate the knob clockwise to increase the cutoff
frequency.
The RES knob controls the resonance of the filter. As the resonance of a filter increases, the filter's output
emphasizes frequencies near its cutoff frequency. In plainer terms, if you turn up the resonance knob, the
filter sounds more “synthy”. (Try it—you'll hear what we mean.) If the filter type is set to 4PLP (see below)
and you turn the resonance knob fully clockwise, the filter will oscillate, producing a sustained tone even if the
plug-in has no input signal.
The TYPE knob switches the filter between several different filter models. As you rotate the knob, watch the
parameter display to see which filter type is active. The available types are:
 Four-pole low pass (shown as “4PLP” in the parameter display) – the filter type most commonly found
in synthesizers. A low-pass filter attenuates or reduces signal frequencies greater than its cutoff
frequency and passes signal frequencies below its cutoff frequency without alteration. As you rotate
the frequency knob clockwise, the filter passes more of the signal's high-frequency content and the
output sounds brighter. If you turn the frequency knob fully counter-clockwise, you may not hear any
output at all because the entire signal has been filtered out.
 Three-pole low pass (shown as “3PLP”): A low-pass filter with a frequency roll-off curve that is less
steep than that of the four-pole filter. Three-pole filters are fairly uncommon, but the three-pole low-
pass filter found in a certain bass-line synthesizer sound defines entire genres of music.
 Two-pole low pass (shown as “2PLP”): A low-pass filter with a frequency roll-off curve that is less
steep than either the three-pole or four-pole low-pass filter. Two-pole filters are usually used for
gentler frequency-shaping applications, such as in equalizers or tone controls, but are found on some
synthesizers.
 Four-pole high pass (shown as “4PHP”): A high-pass filter works in a manner opposite to that of a low-
pass filter: it reduces signal frequencies less than its cutoff frequency and passes signal frequencies
above its cutoff frequency without alteration. As you rotate the frequency knob clockwise, the signal
loses its lower frequencies and the output sounds thinner. If you turn the frequency knob up far
enough, you might not hear anything at all because all of the signal has been filtered out.