sALut
Thank you for purchasing this Xaoc Devices
product. Belgrad is our first all-analog voltage
controlled filter module which—on par with
our other modules—brings something new to
the table. While it can be used as a traditional
VCF for “academic” subtractive synthesis, we
guarantee countless hours of exciting timbral
explorations thanks to its unique character,
flexibility, and features. The most prominent
feature is that it offers a multitude of frequency
responses with two resonant peaks.
instALLAtiOn
The module requires 14hp worth of free space
in the eurorack cabinet. The ribbon type pow-
er cable must be plugged into the bus board,
paying close attention to polarity orientation.
The red stripe indicates the negative 12V rail
and is supposed to point in the same direction
on both the bus board and the unit. The module
itself is secured against reversed power connec-
tion, however reversing the 16-pin header
may
cause serious damage
to other components
of your system, because it will short-circuit the
+12V and +5V power rails. The module should
be fastened by mounting the supplied screws be-
fore powering up. To better understand the de-
vice, we strongly advise the user to read through
the entire manual before using the module.
cOntROLs AnD OPERAtiOn
Belgrad features a pair of state variable
filter cores whose inputs and outputs can
be combined in various serial and parallel
configurations. The mode rotary switch
16
selects one of ten unique filter responses. Turn-
ing the knob from its leftmost position to its
rightmost position consecutively selects modes
that gradually change from lowpass to high-
pass with several more exotic responses in the
intermediate positions.
Different filter responses vary in overall am-
plitude gain and resonance behaviour. There-
fore, you should not be surprised by varying
volume levels after changing modes, especial-
ly when switching from a narrow bandpass to
a narrow notch response. Detailed mode de-
scriptions can be found on pages 5 to 7.
The level knob
1
(fig. 1) controls the am-
plitude of the signal fed into the filter from
the main input
2
up to some degree of in-
put overdrive. The processed signal is avail-
able at the main output socket
3
.
The big freq knob
4
sets the center fre-
quency of both filter cores in the approxi-
mate range of 4Hz to 28kHz. This frequency
can be voltage controlled through the v
·
oct
input
5
and modulated by the fm input
6
(attenuated by the illuminated slider
7
).
Furthermore, both filter cores may be symmet-
rically detuned with respect to the center cutoff
frequency, resulting in a range of interesting
responses, including vocal formants. The de-
tuning is controlled by the deliberately non-lin-
ear span knob
8
as well as the corresponding
bipolar (-5V to +5V) span control voltage in-
put
9
, additionally scaled by the illuminated
attenuator
10
.
2
module
explained
