Filter 8

Joranalogue 12HP
VCF FILTER VCO OSCILLATOR LFO

Verified sheet

The facts on this sheet have been cross-checked against the sources below.

Sources
Suggest a correction

Multimode 4-pole OTA filter with eight simultaneous 45°-spaced outputs. Four cascaded lowpasses plus pole-mixed HP1, band-boost+notch, phase shifter and BP4. Self-oscillates as an 8-phase sine VCO with 1V/oct.

Patch Ideas · 10

★ Resonating envelope bouncer
LOW range · attenuated envelope → IN · LP1 out · add resonance for bounce on transients · switch to AUDIO to superimpose an audio-rate component on the envelope for unique hybrid modulation
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Filter 8, Envelope, Attenuator, VCA. Signals: 3 cv.Filter 8EnvelopeAttenuatorVCALOW/AUDIO: LOWRESONANCE: ~2 o'clockINcvLP1cvOutcvIncvOutcvCVcv11. bouncing envelopecv
Hold-modulated FM bells
AUDIO · res max (oscillator mode) · audio source → HOLD (switch engaged) · tune Filter 8 and source to a just interval · apply matched V/oct FM · produces 'bell' and 'synthetic bass' tones somewhere between linear FM and hard sync
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Filter 8, Sequencer, Modulator VCO, VCA. Signals: 2 audio, 2 pitch.Filter 8SequencerModulator VCOVCALOW/AUDIO: AUDIORESONANCE: maxHOLD switch: ONV/OCT.1v/octHOLDaudioBP4audioPitch1v/octV/Oct1v/octOutaudioInaudioaudiopitch
Feedback drive
Audio source → IN · LP4 → attenuator → spare IN (feedback) · attenuator sets 'drive' · swap in a VCA on feedback path for voltage-controlled tone · try different outputs as feedback source for timbre variation
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 5 connections. Modules: Filter 8, VCO, VCA, Envelope, Output. Signals: 4 audio, 1 cv.Filter 8VCOVCAEnvelopeOutputLOW/AUDIO: AUDIORESONANCE: highINaudioLP4audioOutaudioInaudioCVcvOutaudioOutcvInaudio11. VC drive amountaudiocv
★ Saw-wave 8-phase VCO
AUDIO · res max · inputs unpatched · BP4 → EFM input (max EXP. FM) · LP2 and BB+N become near-perfect saw waves · pitch tracks with FM depth affecting V/oct · a chaotic saw bank
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Filter 8, Sequencer, External Filter, Mixer. Signals: 2 audio, 1 cv, 1 pitch.Filter 8SequencerExternal FilterMixerLOW/AUDIO: AUDIORESONANCE: maxCOMP.: ONEXP. FM: maxV/OCT.1v/octEFMcvBP4cvLP2audioBB+NaudioPitch1v/octInaudioInaudio121. saw-like2. waveshape feedbackaudiocvpitch
Multi-timbral kick + bongo ping
AUDIO · res just past 3 o'clock panel mark · COMP off · trigger → PING · LP4 drives the kick (big transient) · BP4 drives bongo-like tom · each output is its own drum voice from the same strike
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Filter 8, Clock, LFO, Mixer. Signals: 2 audio, 1 cv, 1 trigger.Filter 8ClockLFOMixerLOW/AUDIO: AUDIORESONANCE: just past 3 o'clockCOMP.: OFFPINGtrigV/OCT.cvLP4audioBP4audioOuttrigOutcvInaudio1231. pitch tuning2. kick3. bongoaudiocvtrigger
Phaser voice
AUDIO · moderate res · audio → IN · PS output = built-in one-stage phaser · slowly modulate V/OCT with an LFO for classic phaser sweep · chain a second Filter 8 for deeper phasing
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Filter 8, VCO, LFO, Mixer. Signals: 2 audio, 1 cv.Filter 8VCOLFOMixerLOW/AUDIO: AUDIORESONANCE: moderateINaudioV/OCT.cvPSaudioOutaudioOutcvInaudio11. phaser voiceaudiocv
Custom response via pole mixing
Audio → IN · send several LP outputs + IN into external VC mixer · use different modulation on each channel to morph the response in real time · recreate or exceed vintage multimode filters
▸ Show diagram
Patch diagramPatch diagram with 6 modules and 8 connections. Modules: Filter 8, VCO, VC Mixer, LFO 1, LFO 2, Output. Signals: 6 audio, 2 cv.Filter 8VCOVC MixerLFO 1LFO 2OutputLOW/AUDIO: AUDIORESONANCE: tasteINaudioLP1audioLP2audioLP4audioHP1audioOutaudioIn 1audioIn 2audioIn 3audioIn 4audioCV 1cvCV 2cvOutaudioOutcvOutcvInaudioaudiocv
★ 8-phase LFO bus
LOW · res max · COMP on · inputs unpatched · eight 45°-offset LFOs · route to eight destinations (pan, FX send, filter, wavefolder, etc.) for phase-related global motion
▸ Show diagram
Patch diagramPatch diagram with 7 modules and 8 connections. Signals: 8 cv.Filter 8PanVCAExternal FilterFXVCOWavefolderLOW/AUDIO: LOWRESONANCE: maxCOMP.: ONLP1cvLP2cvLP3cvLP4cvHP1cvBB+NcvPScvBP4cvCVcvCVcvCutoffcvRescvTimecvFMcvCVcvcv
Sync-effect via HOLD
AUDIO · res mid · audio → IN · another VCO square → HOLD · HOLD switch routing ON · filter core freezes on each rising edge → sync-like rhythmic stutter on the filtered audio · detune HOLD source for beating
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Filter 8, VCO A, VCO B, VCA. Signals: 2 audio, 1 gate.Filter 8VCO AVCO BVCALOW/AUDIO: AUDIORESONANCE: ~noonHOLD switch: ONINaudioHOLDgateLP4audioOutaudioSquaregateInaudioaudiogate
Decaying 8-phase sine modulator
LOW · res near self-osc · trigger → PING · ping excites a decaying multi-phase sine burst across all outputs · patch pairs to destinations for gently-ringing organic modulation on key events
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 4 connections. Modules: Filter 8, Gate Seq, External Filter, VCA, Pan. Signals: 3 cv, 1 trigger.Filter 8Gate SeqExternal FilterVCAPanLOW/AUDIO: LOWRESONANCE: just past 3 o'clockPINGtrigLP1cvLP3cvBP4cvOuttrigCutoffcvCVcvCVcvcvtrigger

Behaviors

8-phase sine VCO resonance max · inputs unpatched

Self-oscillates with 1V/oct tracking over ≥5 octaves. All eight outputs emit sine waves separated by 45°. With COMP engaged, amplitudes match — a complete 8-phase oscillator bank.

Simultaneous multimode normal filter operation

Every jack emits its response at all times. Patching LP4 and HP1 to separate destinations gives independent LP/HP filtering of the same signal, useful for bi-timbral voices.

Resonance without LF loss RESONANCE knob CW

Unique feedback topology keeps low-frequency content intact as resonance rises, unlike classic OTA filters that thin out. Lets you push resonance without bass drop.

Input mix/drive two signals into both INs

Input jacks sum internally — no mixer needed. Hot signals can clip the core; when resonance adds gain this becomes musical distortion. Lower amplitudes to avoid, or embrace it.

Filter ping rising edge → PING · res just below self-osc

Each output generates a different ping timbre: LP1–LP4 have percussive transients (kick-drum material), BP4 is purest (bongo/tom), BB+N behaves best with COMP on. COMP off elsewhere to avoid transient distortion.

Hold freeze HOLD gate or switch

Freezes the filter core at its instantaneous state. Halts slow modulations; at audio rate creates sync-like effects. Driving HOLD with audio pulses in oscillator mode yields FM-sync hybrid tones.

Linear FM with AC coupling LFM input + AC switch

LFM keeps perceived pitch centred during deep modulation. AC switch removes DC drift so the fundamental doesn't wander. Rev D firmware fix removed a freeze bug at ~+10V LFM.

LF slew modifier / 8-phase LFO LOW range · signal → IN

In LOW mode the filter slews incoming envelopes or gates. Resonance adds bounce. Self-oscillating LOW gives an 8-phase LFO array for quadrature-plus-rich modulation.

Output distortion as drive harmonically rich hot input

Because outputs are unity gain (COMP off), removing harmonics can raise amplitude and clip. Useful as intentional overdrive on saws/pulses through LP4.

Controls

Global LOW/AUDIO Switch Selects filter/VCO audio range or slew-modifier/VCLFO range.
AUDIO: 22Hz–22kHz · LOW: 2.8mHz–180Hz · 1Hz at centre in LOW
frequency COARSE Sets filter/oscillator frequency. 22Hz–22kHz in audio when FINE centred.
Audio: 22Hz–22kHz · Low: 2.8mHz–180Hz
frequency FINE 5 % fine-tune around COARSE. Roughly ±6 semitones in audio.
5% of COARSE range · centre = no offset
feedback RESONANCE Feedback from output back to input. Above ~3 o'clock self-oscillates (panel mark).
Unique circuit: no LF loss as resonance rises
exp FM knob EXP. FM Polariser for the EFM CV input. Second exponential FM path with depth.
noon: 0 · max: +1V/oct · min: −1V/oct · 0.66V/oct in LOW
linear FM knob LIN. FM Polariser for the LFM CV input. ~±7%/V — 'tonal' FM that holds pitch centre.
bipolar · ~±7 % freq/V
linear FM AC Switch AC-couples the LFM input to reject DC drift during audio-rate linear FM.
Engage for clean linear FM · bypass for DC control
resonance CV RES. MOD. Polariser for the resonance CV input.
bipolar · +5V at CV = max resonance
output gain COMP. Switch Enables gain compensation: all outputs equal amplitude when self-oscillating.
OFF: unity gain per output · ON: matched amplitude for 8-phase VCO use
hold HOLD Switch Manually freezes filter core, or enables/disables the HOLD gate input.
Toggles manually · with HOLD patched, switch routes the gate
calibration V/OCT Trimmer Front-panel pitch-tracking trim. Factory calibrated.
Target: 4 octaves between 0V and +4V on V/OCT
calibration RES. Trimmer Front-panel trim for self-oscillation amplitude at max resonance.
Target: BP4 = 10Vpp sine · not temp-compensated

I/O

IN · 7

  • V/OCT. 1V/oct · 0.66V/oct in LOW CV
    Precision 1V/oct exponential FM. Usable as VCO pitch input.
  • EFM bipolar CV CV
    Second exponential FM input, scaled by EXP. FM polariser knob.
  • LFM bipolar CV · ~±7%/V CV
    Linear FM input, polarised by LIN. FM knob. AC-coupleable via AC switch.
  • RES. MOD. bipolar · +5V = max CV
    Resonance modulation input, polarised by RES. MOD. knob.
  • IN (×2) any audio/CV · 100kΩ CV
    Two identical signal inputs, mixed internally. Can clip on rich high-level signals as a deliberate drive effect. Unpatched for pure oscillator mode.
  • HOLD +2V low / +3V high · Schmitt trigger GATE
    Rising edge freezes filter core at current state. Schmitt-triggered for weak/slow signals.
  • PING rising edge above +3V
    Rising edge above +3V 'strikes' the filter core for percussive ping tones. Set resonance just below self-osc.

OUT · 8

  • LP1 45° phase at cutoff
    1-pole lowpass. −6dB/oct. Softest filtering.
  • LP2 90° phase at cutoff
    2-pole lowpass. −12dB/oct.
  • LP3 135° phase at cutoff
    3-pole lowpass. −18dB/oct.
  • LP4 180° phase at cutoff
    4-pole lowpass. −24dB/oct. Steepest classic-Moog-style response.
  • HP1 225° phase
    1-pole highpass (pole-mixed). Gentle highpass; resonates at 225°.
  • BB+N 270° phase
    Band-boost + notch. Boost just below cutoff, cut just above. Wavefolder-like at high res.
  • PS 315° phase
    Phase shifter: 3-pole allpass summed with input. One-stage phaser response.
  • BP4 360° phase · purest self-osc sine
    4-pole bandpass. Purest sine at self-oscillation. 360° (0°) phase.