Amplitude Control - Xaoc Devices KATOWICE Operator's Manual

quencies, and the right high slider
11
CV input control the high frequencies. The
middle band signal is available at the stereo
pair of mid outputs
band and high band are available at their
stereo pairs of low and high outputs
and 14 . A stereo mixdown of the three bands
(post-VCA) is available at the sum pair of
outputs 15 .
fIlTErInG
Splitting the signal into separate frequency
bands is implemented with a set of special
voltage–controlled crossover filters. They
are designed so that with no attenuation, the
sum of all three bands reconstructs the origi-
nal signal without any gaps in the spectrum.
The frequency responses of all three bands
are non-resonant and flat in the passband.
They all offer a 24dB/octave slope beyond
their cutoff frequencies (see fig. 2).
Keep in mind that the mid freq controls
(knob and CV input) define the geometric cen-
ter of the mid band (the middle point in the
exponential frequency scale). For example,
when mid freq is set to 2kHz and the mid
width is 2 octaves, the mid band spans from
1kHz to 4kHz (measured at –6dB split point).
When CV inputs are used, manual controls act
as offsets. There is a global limit of the split
frequencies meaning that they cannot extend
below 30Hz and above 20kHz. Also, the mini-
mum width of the mid band is 1 octave.
10
and
12 . Similarly, the low

AmPlITudE COnTrOl

Katowice offers independent amplitude
control for each of its three bands. A slider
in each band allows for attenuation of the
signal down to about –100dB. The response
13
of this potentiometer is carefully bent to
provide the natural feel of a fader. This at-
tenuation may also be achieved by patching
a negative CV to the corresponding jack. Con-
versely, when the slider is set near the bot-
tom, a positive CV will bring the signal back.
The response of the VCA is exponential and a
voltage of 8V opens it entirely to unity gain.
In order to prevent hard clipping, each VCA
channel features a soft-saturation circuit
that rounds the peaks of signals approach-
ing 18Vpp.
Katowice ships factory calibrated so that the
maximum gain is hard limited at 0dB. The
trimmer at the back allows for shifting the
gain range (including the limit) up to ±20dB.
fig. 2: example frequency response
20
dB
10
0
-10
-20
-30
-40
-50
-60
10
4
mid width
mid freq
100 1000
Hz
10000