XAOC Devices Belgrad
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.
