Déjà Vu

Bastl Instruments 4HP
ATTENUATOR ATTENUVERTER MIXER UTILITY

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Dual fader utility with voltage source behavior, attenuator, attenuverter, crossfader, preamp gain up to 10x, cascading outputs, and CV or audio processing in 4HP.

Patch Ideas · 5

★ Voltage offset pair
Leave both FADER inputs open · set each fader to different positions · use the two channels as offset sources for pitch or filter modulation · a tiny analog bias box with hands-on control.
Walkthrough
  1. Set FADER MODE on both channels to attenuator.
  2. Set FADER GAIN on both channels to 1x.
  3. Leave FADER A and FADER B inputs unpatched (so the faders become voltage sources).
  4. Patch an LFO → Déjà Vu ADD A (the LFO rides on top of the channel-A offset).
  5. Patch Déjà Vu OUT A → Filter CUTOFF.
  6. Patch Déjà Vu OUT B → VCO FINE TUNE or another CV destination (fader B is a pure manual offset).
  7. Ride FADER A to set LFO depth/bias, ride FADER B to hand-tune the destination.
Signal out OUT A — LFO + manual bias, CV. OUT B — static manual offset, CV for any modulation destination.
Listen for Filter cutoff breathing around a position you set with FADER A, and a second parameter you nudge in real time by sliding FADER B. Green/red LEDs show polarity.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Déjà Vu, LFO, Filter, VCO. Signals: 3 cv.Déjà VuLFOFilterVCOFADER A MODE: attenuatorFADER B MODE: attenuatorFADER GAIN: 1xADD AcvOUT AcvOUT BcvOutcvCutoffcvFine Tunecvcv
★ Crossfade macro
Use channel A as a crossfader between two modulation sources · feed the result into channel B for fine trimming · one fader performs the macro move while the second sets the final range.
Walkthrough
  1. Set FADER A MODE to crossfader (blends FADER A against ADD A).
  2. Set FADER B MODE to attenuator (B trims the final depth).
  3. Set both FADER GAIN switches to 1x.
  4. Patch LFO → Déjà Vu FADER A (source 1 of the crossfade).
  5. Patch Envelope → Déjà Vu ADD A (source 2 of the crossfade).
  6. Patch Déjà Vu OUT A → Déjà Vu FADER B.
  7. Patch Déjà Vu OUT B → Filter CUTOFF.
  8. Move FADER A to morph between LFO and envelope modulation. Use FADER B to set overall depth.
Signal out OUT B — a single macro CV that crossfades between LFO and envelope modulation, scaled by FADER B.
Listen for Filter movement that morphs from continuous LFO sway to punchy per-note envelope bumps as you slide FADER A, while FADER B sets how strong the whole effect is.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Déjà Vu, LFO, Envelope, Filter. Signals: 4 cv.Déjà VuLFOEnvelopeFilterFADER A MODE: crossfaderFADER B MODE: attenuatorFADER GAIN: 1xFADER AcvADD AcvFADER BcvOUT AcvOUT BcvOutcvOutcvCutoffcvcv
Stereo line preamp
Use the 10x gain setting to lift line-level or quiet synth sources into modular level · channel A and B handle left and right paths separately · useful before an effect return or mixer insert.
Walkthrough
  1. Set FADER A MODE and FADER B MODE to attenuator.
  2. Set both FADER GAIN switches to 10x (low-noise preamp).
  3. Patch Line Source L → Déjà Vu FADER A.
  4. Patch Line Source R → Déjà Vu FADER B.
  5. Patch Déjà Vu OUT A → Output mixer L.
  6. Patch Déjà Vu OUT B → Output mixer R.
  7. Slide FADER A and FADER B up from zero until the green LEDs peak without flashing hard red on the loudest passages.
Signal out OUT A / OUT B — line-level stereo signal boosted to eurorack level, ready for a mixer or effect return.
Listen for A previously-too-quiet external synth or phone output sitting at modular level with clear stereo — bright green LEDs on peaks, no obvious noise floor thanks to the low-noise preamp.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Déjà Vu, Source L, Source R, Output. Signals: 4 audio.Déjà VuSource LSource ROutputFADER A MODE: attenuatorFADER B MODE: attenuatorFADER GAIN: 10xFADER AaudioFADER BaudioOUT AaudioOUT BaudioOutaudioOutaudioLaudioRaudioaudio
★ Cascade 4-input mixer
Patch several sources into A and B, leave OUT A unpatched, and let the cascade jumper fold both channels into a small mixer. The module turns into a compact two-stage mix block.
Walkthrough
  1. Confirm the rear CASCADING OUTPUT JUMPER is set to ON (factory default on most units).
  2. Set FADER A MODE and FADER B MODE to attenuator.
  3. Set both FADER GAIN switches to 1x (raise if sources are quiet).
  4. Patch Source 1 → Déjà Vu FADER A, Source 2 → Déjà Vu ADD A.
  5. Patch Source 3 → Déjà Vu FADER B, Source 4 → Déjà Vu ADD B.
  6. Leave Déjà Vu OUT A unpatched so channel A cascades into B.
  7. Patch Déjà Vu OUT B → Output (In).
  8. Use FADER A to balance sources 1 vs 2 (A sub-mix), FADER B to set channel B level in the final mix; ADD levels are fixed unity sums.
Signal out OUT B — mono sum of up to four inputs, with FADER A acting as a sub-mix level for A into B and FADER B as the channel-B level.
Listen for A four-into-one mix in 4HP. FADER A controls how loud the sources patched into A appear in the final mix; FADER B controls the channel-B pair. OUT B's LED shows overall level.
▸ Show diagram
Patch diagramPatch diagram with 6 modules and 5 connections. Modules: Déjà Vu, Source 1, Source 2, Source 3, Source 4, Output. Signals: 5 audio.Déjà VuSource 1Source 2Source 3Source 4OutputFADER A MODE: attenuatorFADER B MODE: attenuatorCascading jumper: ONFADER AaudioADD AaudioFADER BaudioADD BaudioOUT BaudioOutaudioOutaudioOutaudioOutaudioInaudioaudio
Bias and boost
Bias a hot audio signal with the fader's voltage-source behavior and push it into an ADD input from another oscillator or envelope · the result is a simple offset-and-gain stage with a very direct feel.
Walkthrough
  1. Set FADER A MODE to attenuverter (bipolar processing of FADER A).
  2. Set FADER A GAIN to 2x to lift the signal after processing.
  3. Patch VCO → Déjà Vu FADER A.
  4. Patch Envelope → Déjà Vu ADD A (the envelope offsets/biases the audio path).
  5. Patch Déjà Vu OUT A → Filter / Output.
  6. Centre FADER A and move it up (positive) or down (inverted) to attenuvert the VCO; nudge FADER B (unpatched) only if you want its voltage to bias — not needed here.
Signal out OUT A — VCO attenuverted by FADER A plus the envelope added in at unity, at 2x gain.
Listen for A VCO that can be swept through silence and into polarity-inverted territory by FADER A, with an envelope bump from ADD A adding a per-note bias — saturating gently thanks to the 2x boost.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Déjà Vu, VCO, Envelope, Output. Signals: 2 audio, 1 cv.Déjà VuVCOEnvelopeOutputFADER A MODE: attenuverterFADER GAIN: 2xFADER AaudioADD AcvOUT AaudioOutaudioOutcvInaudioaudiocv

Behaviors

Voltage source mode leave FADER input unpatched

The fader becomes a static voltage source instead of a level control, so each channel can act as an offset or bias generator — or the fader acts as a manual level for whatever is patched into ADD.

Three-way fader behavior switch FADER MODE

The same channel can act as an attenuverter, attenuator, or crossfader between FADER and ADD, which keeps the panel useful for both audio and CV duties.

Preamp gain raise FADER GAIN

The channel can boost incoming audio up to 10x with a low-noise preamp, making it usable as a line-level to eurorack-level booster as well as a utility attenuator.

Cascade mixer leave OUT A unpatched (cascade jumper on)

Channel A mixes into channel B output, effectively turning the pair into a 4-input mixer (FADER A + ADD A + FADER B + ADD B → OUT B).

CV or audio utility patch either audio or control voltages

The module processes both CV and audio cleanly, so it works as a bias box, crossfade pair, gain stage, stereo panner, or small mixer.

Polarity LED indication observe OUT LEDs

Each output LED glows green for positive voltage and red for negative, with brightness tracking magnitude — a visual meter for attenuverter, offset and crossfade positions.

Controls

Channel A/B FADER Sets the channel level or crossfade position depending on mode.
voltage source when unpatched
Channel A/B FADER MODE Switches between attenuverter, attenuator, and crossfader behavior.
attenuverter · attenuator · crossfader
Channel A/B FADER GAIN Sets the gain stage for the fader path.
1x · 2x · 10x · 10x reducible to 5x via rear jumper
Rear jumper Cascading output jumper Routes channel A into channel B when OUT A is left unpatched.
cascading mix on/off

I/O

IN · 4

  • FADER A CV / audio CV
    Main fader input for channel A. Normalled to a voltage source when unpatched.
    NORM → voltage source
  • ADD A CV / audio CV
    Auxiliary input summed after the fader path on channel A (or second side of the crossfade in crossfader mode).
  • FADER B CV / audio CV
    Main fader input for channel B. Normalled to a voltage source when unpatched.
    NORM → voltage source
  • ADD B CV / audio CV
    Auxiliary input summed after the fader path on channel B (or second side of the crossfade in crossfader mode).

OUT · 2

  • OUT A CV / audio CV
    Channel A output with green/red polarity LED indication.
  • OUT B CV / audio CV
    Channel B output with green/red polarity LED. Channel A is mixed in when OUT A is unpatched and the cascading jumper is enabled.