xaoc-devices/belgrad
Belgrad
Dual peak multimode state variable filter with two analog filter cores, 10 distinct frequency responses, voltage control over resonance and peaks balance, nonlinear feedback and cross-modulation, and adjustable input overdrive. Model of 1976.311
Visualization filter_response
Capabilities 2
- Self-Oscillationself-oscillation
- At reso around 8, the filter self-oscillates as one or two sine wave VCOs tracking approximately five octaves via v·oct input.311
- Voltage-Controlled Filtervoltage-controlled-filter
- Dual-core analog state variable filter with 10 distinct frequency responses, voltage control over frequency, resonance, and peaks balance.311
Jacks 7 — 6 in / 1 out
| Name | Signal | Voltage | Description |
|---|---|---|---|
| Inputs (6) | |||
| balance input | cv | -5V to 5V | 311 |
| fm | cv | — | FM input for modulation of the center frequency, attenuated by the illuminated slider.311 |
| main input | audio | — | 311 |
| reso | cv | 0V to 8V | 311 |
| span cv | cv | -5V to 5V | 311 |
| v·oct | cv | — | V/octave input for voltage control of the center frequency of both filter cores. Also controls pitch when self-oscillating.311 |
| Outputs (1) | |||
| main output | audio | — | 311 |
Parameters 9
| Name | Type | Range | Behavior |
|---|---|---|---|
| balance | knob | — | Sets the relative emphasis of the two resonant peaks, from domination of the lower peak through full symmetry to domination of the higher peak. Can be voltage controlled via the balance input.311 |
| fm attenuator | fader | — | Illuminated slider that attenuates the FM input signal applied to the center frequency.311 |
| freq | knob | 4Hz – 28000Hz | Sets the center frequency of both filter cores. Can be voltage controlled via v·oct input and modulated by fm input.311 |
| level | knob | — | Controls the amplitude of the signal fed into the filter from the main input, up to some degree of input overdrive.311 |
| mode | switch | 1 – 10 | Rotary switch selecting one of 10 filter responses, progressing from lowpass to highpass with exotic intermediate responses.311 |
| reso | knob | — | Sets the overall degree of resonance. Around value 8 the filter begins to self-oscillate, behaving like one or two sine wave VCOs. Driving further reveals nonlinear distortion in the feedback paths.311 |
| span | knob | 0octave – 8octave | Deliberately non-linear knob that symmetrically detunes the two filter cores relative to the center frequency, setting the distance between the two resonant peaks from zero up to nearly eight octaves.311 |
| span cv attenuator | fader | — | Illuminated attenuator that scales the span CV input.311 |
| tito | switch | — | Three-position switch controlling internal coupling topology. Neutral position is off; up selects self-modulation (sm) giving radical, textured resonance; down selects cross-modulation (xm) adding warbly, chirpy character.311 |
Firmware history 0 versions
No firmware history recorded.
References 2
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[311]
Xaoc Belgrad Operator's Manual rev. 1976/1.5 (dual peak multimode SVF)manual● verified 2026-05-11
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[312]
Xaoc Devices Belgrad product pageproduct_page⚠ verified 2026-05-11 · manufacturer changed since last verified