M-Audio Wayoutware TimewARP 2600 User Manual page 24

3.6.3.1 Gain Factor
To describe the behavior of an amplifier or attenuator, we may use the expression "gain factor" to mean the ratio
of output signal amplitude to input amplitude.
3.6.4 Filters
A filter is a device that works better at some frequencies than at others. (The inverters, mixers, and attenuators we
have been describing work the same at all frequencies, so they are not filters.)
Because of this frequency-dependent characteristic of filters, they change the shape of any complex waveform
passing through. And so it will be important for you to get to know what filters do to signals in both the time
domain and in the frequency domain.
3.6.4.1 Low-Pass Filters
Any device or mechanism that passes along slower motions better than faster ones can act as a lowpass filter.
Picture yourself stirring a cup of tea with one of those little wooden paddles they hand out in the coffee shops. Stir
it back and forth, fast. Now slow down. Now imagine the tea has turned to syrup. You can still stir it slowly, but if
you try to go fast the stick will simply not move.
That's a lowpass filter. You can see the effect of this on a signal quite easily.
For audio signals, you will usually be more interested in the frequency-domain effects of filtering. For subaudio
signals, it is usually the time-domain effects—changes in waveshape—that we care about. In the time domain, a
low-pass filter rounds off any sharp transitions in the signal. A good example of this is the lag processor described
in section 3.6.4.5 below.
In the frequency domain, it weakens spectral components that are higher than the filter cutoff frequency—the
frequency at which the filter begins to have an effect on the signal.
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