XAOC Devices Belgrad

Name: Belgrad
Brand: XAOC Devices

Dual peak analog state variable filter with wild character

14 HP Eurorack module

Belgrad is an all-analog dual-core state variable filter for Eurorack, featuring two resonant peaks whose frequency distance, balance, and character can be continuously voltage-controlled. It offers ten distinct filter responses ranging from lowpass to highpass with exotic intermediate modes, and includes nonlinear feedback and cross-modulation features that push it well beyond conventional subtractive filtering into expressive, vocal, and chaotic sonic territory.

Features

All-analog dual-core state variable filter design
10 distinct frequency responses from lowpass to highpass
Two simultaneous resonant peaks
Span control for symmetrical detuning of filter cores up to nearly eight octaves
Balance control for asymmetric resonance emphasis between the two peaks
Wide tuning range approximately 4Hz to 28kHz
V/octave tracking input for musical pitch control
FM input with illuminated attenuator slider
Span CV input with illuminated attenuator
Resonance CV input (0 to 8V)
Balance CV input (bipolar -5V to +5V)
Self-oscillation with approximately 5-octave V/oct tracking

Controls & Jacks (17)

Main Input— Main audio signal input to the filter
Balance CV— Bipolar (-5V to +5V) control voltage input for peak balance symmetry
Frequency— Sets the center frequency of both filter cores in the range of approximately 4Hz to 28kHz
Span— Controls the nonlinear detuning between the two filter cores, creating formant-like responses with a range of nearly eight octaves
Resonance CV— Control voltage input for resonance (0 to 8V range)
V/Oct— Voltage-per-octave control input for frequency tracking
Level— Controls the amplitude of the signal fed into the filter from the main input, with overdrive capability
FM Attenuator— Illuminated slider that attenuates the FM modulation input signal
Main Output— Processed audio signal output from the filter
FM— Frequency modulation input, attenuated by the FM slider
Span CV— Bipolar (-5V to +5V) control voltage input for span detuning, scaled by the span attenuator
Balance— Sets the emphasis balance between the two resonant peaks, from lower peak domination through symmetry to upper peak domination
TITO— Toggles between neutral, self-modulation (SM), and cross-modulation (XM) for internal audio-rate coupling and nonlinear effects
TITO— Toggles between neutral, self-modulation (SM), and cross-modulation (XM) for internal audio-rate coupling and nonlinear effects
Resonance— Controls the overall degree of resonance; at around position 8 the filter begins to self-oscillate
Mode— Rotary switch selecting one of ten unique filter responses, from lowpass to highpass with exotic responses in intermediate positions
Span— Controls the nonlinear detuning between the two filter cores, creating formant-like responses with a range of nearly eight octaves

How-To Guides

Vocal Formant Sweep
Self-Oscillating Dual VCO
Variable Phaser or Double Notch
Drum Transient Mangler with XM
Chaotic Self-Oscillation in HH or BH
Sweeping Band Rejection Filter
4-Pole to 2-Pole Lowpass Morph
Bass Fattening with Input Overdrive
Dynamic Resonance Envelope
Asymmetric Balance Formant Voice

Explore the interactive Belgrad panel on BleepDex — tap any control to learn what it does.