FUNS
The FUN Equations
17-9
Figure 17-5 hipass (f = a, b)
b / (1 - a)
This is another weighted difference equation similar to the first six. The value of Input a is
subtracted from 1. The value of Input b is then divided by the difference. You’ll get considerably
different results for different input values of a and b.
a(b-y)
Think of this equation as reading “y is replaced by the result of the function a(b-y).” The value of
y indicates the value of the FUN’s output signal. Every 20 milliseconds, the K2661 takes the
current value of y, runs the equation, calculates a new value of y, and inserts the new value into
the equation. Consequently the value of y will change every twenty milliseconds. Here’s an
example. When you play a note, the K2661 starts running the FUN. The first value for y is
always 0. We’ll assume the value of Input a is +.5, and the value of Input b is +1. The first time
the K2661 evaluates the FUN, the result of the equation is .5 x (+1 - 0), or .5. So the FUN’s output
value after the first evaluation is .5. This becomes the new value for y, and when the K2661 does
its next evaluation of the FUN, the equation becomes .5 x (+1 - .5), or .25. The resulting output
value is .25, which becomes the new value for y. For the next evaluation, the equation is .5 x (+1-
.25), or .375.
(a + b)^2
The values of Inputs a and b are added, and the result is squared (multiplied by itself). This will
change the linear curve of a unipolar control signal into a curve that’s lower at its midpoint (by a
factor of 2). Bipolar control signals will generate curves that are high at both ends, and 0 in the
middle.
1)
4)3)
2)
input b
value
time
input b
value
time
input b
value
time
input b
value
time
To Next Page
Loading...
