sAlut
Thank you for purchasing this Xaoc Devices
product. Zagrzeb is a stereo multimode 4-pole
(24dB/oct) state variable voltage-controlled fil-
ter (SV VCF). It offers five distinct frequency re-
sponses, three of which are available simultane-
ously. Zagrzeb is designed to sound smooth and
clean unless it is overdriven with a hot signal—
however, it does not lack character! We believe
it will be appreciated by fans of old Japanese
synthesizers but bear in mind that Zagrzeb is
not a clone of any existing design. The four-pole
state variable structure is a new development
and offers unique sonic characteristics. While
Zagrzeb is designed for filtering stereo signals
(e.g. samples or stereo oscillators like Xaoc
Odessa), it can easily handle mono signals and
is capable of creating a faux stereo pair thanks
to a special phase shifting network at the input.
instAllAtiOn
The module requires 8hp worth of free space in
the Eurorack cabinet. Always turn the power off
before plugging the module to the bus board
using the supplied ribbon cable paying close at-
tention to power cable pinout and orientation.
The red stripe indicates the negative rail and
should match the dot or –12V mark on the bus
board as well as the unit. Zagrzeb is internally
secured against reversed power connection,
however flipping the 16-pin header
may cause
serious damage
to other components of your
system, because it will short circuit the +12V and
+5V power lines. Always pay particularly close
attention to the proper orientation of your rib-
bon cable on both sides! The module should be
fastened by mounting the supplied screws before
powering up. To better understand the device,
we strongly advise the user to read through the
entire manual before use.
mODulE OVERViEW
Zagrzeb’s front panel is shown in fig. 1. The
stereo pair of left/mono and right signal
inputs
1
is AC-coupled and accepts all Eu-
rorack signal levels (up to 20Vpp), however, a
conservative 10Vpp level is recommended as
filtering certain signals may occasionally yield
increased amplitude thus causing distortion.
With a mono signal patched into the left/
mono jack the module automatically creates
a stereo signal. The three pairs of jacks below
the inputs are the high pass 24
2
, band
pass
3
, and low pass 24
4
outputs of
the filter. The bp config switch
5
near the
band pass outputs offers three variants of this
middle type of response. The big cutoff freq
knob below
6
controls the cutoff frequency of
the filter (10Hz to 20kHz) while the vertical
resonance slider
7
controls the degree of
resonance. The illuminated slider shaft indi-
cates how much the peaks of the output signal
exceed the peaks of the input signal (mostly
due to the resonant ringing around the cut-
off frequency). The fm 1
8
and fm 2
9
CV
inputs at the bottom of the panel control the
cutoff frequency. The sensitivity of the fm 1
input is controlled by the small attenuverter
knob
10
from –2 oct/V through 0 to +2 oct/V.
The fm 2 input is fixed at 1V/oct (uncalibrat-
ed). The spread CV input
11
allows the user
to animate the stereo image by moving the left
and right filter cutoff frequencies in opposite
directions.
fREQuEncY REsPOnsE
Zagrzeb is a state variable filter, hence it of-
fers multiple outputs. Common 2-pole filters
offer –12dB/oct low pass, +6/–6dB band pass,
and +12dB/oct high pass responses. Zagrzeb’s
4-pole structure gives the user as many as
five different characteristics: from –24dB/oct
low pass up to +24dB/oct high pass with all
three possible combinations of 6dB/oct slopes
that sum up to 24 in between. These interme-
diate combinations are different variants of
band pass (an asym6/–18dB, a sym-
12/–12dB, and another asymmetric
2
module
explained
