Owner`s manual

CHAPTER 3 -
21
CHAPTER 3 -
The Craft of audio Synthesis
3.6.2
Signal Mixing
A signal mixer adds two or more signals together and outputs the result of the addition.
This is a more complex signal, usually, than any of the inputs. But not necessarily; if
signal B, for example, is the exact inversion of signal A, then mixing the two will produce
a signal of exactly zero.
3.6.3
Attenuators/Ampli ers
An attenuator cuts the strength of a signal passing through. Digitally, this is accomplished
by multiplying the input by some value ranging from 0.0 (which passes no signal) to 1.0
(which passes the signal at its full input amplitude).
An ampli er may increase the amplitude of a signal. But not necessarily; it is usual for a
voltage-controlled ampli er to have a maximum gain factor of 1.0. In fact, the purpose of
VCA’s is actually to “chop” the signals passing through them. It would make more sense
to think of them as “voltage controlled attenuators”.
3.6.3.1
Gain Factor
To describe the behavior of an ampli er 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  lter 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  lters.)
Because of this frequency-dependent characteristic of  lters, they change the shape of
any complex waveform passing through. And so it will be important for you to get to
know what  lters do to signals in both the time domain and in the frequency domain.
Inverters
input
input
output
output
these four
signals added
(mixed)
together make....
two sines
added together