doepfer-a-185-2

Doepfer A-185-2 Precision Adder / Bus Access

Precision CV summing with bus access and octave switching

6 HP Eurorack module

The A-185-2 Precision Adder / Bus Access is a utility module that sums up to four CV or audio signals with extreme voltage accuracy, making it ideal for combining pitch CVs without tuning errors. Each input channel has a three-position switch (positive, off, negative) allowing addition or subtraction of signals, and the module also provides direct access to the A-100 bus CV for integrating MIDI-to-CV data from the bus. Its precision trimming ensures octave-accurate transposition when used in V/Oct pitch contexts.

Features

  • Four-channel precision CV/audio summing with overall gain trimmed to exactly 1.00 via P1
  • Each channel has a three-position switch: positive addition, off, negative subtraction
  • Internal +1.000V precision reference for octave transposition when input jack is unplugged
  • P2 trimmer for calibrating the internal +1.000V octave reference
  • Non-inverting (+) and inverting (-) outputs provided simultaneously
  • A-100 bus CV access via JP5 jumper (normal or inverted polarity)
  • Bus board connection via JP1 ribbon cable (red stripe = bottom)
  • Switching contacts on input sockets activate internal reference when jack is removed
  • Suitable for precision V/Oct pitch CV summing and transposition
  • Offset voltage compensation included in calibration procedure

Controls & Jacks (25)

  • Channel 1— Three-position switch for Channel 1 input selection: left (−), center (off), right (+).
  • Channel 1 Input— Adjusts overall gain to exactly 1.00. Trim potentiometer for precise calibration.
  • Channel 2— Audio/CV input for Channel 1
  • Channel 2 Input— Non-inverting summed output
  • Channel 3— Audio/CV input for Channel 2 (switches to +1.000V when empty)
  • Channel 3 Input— Audio/CV input for Channel 3
  • Channel 4— Audio/CV input for Channel 4
  • Channel 4 Input— Inverting summed output
  • Output (+)— Bus control voltage output
  • Output (−)— Inverting summed output
  • P1 Overall Amplification— Adjusts 1.000V reference for octave switching. Trim potentiometer for precise calibration.
  • Bus CV Output
  • P2 Octave Interval— Adjusts 1.000V reference for octave switching. Trim potentiometer for precise calibration.
  • JP1 Bus Connection— Pin header for connection to bus board (red stripe = bottom position).
  • JP5 Bus CV Connection— Jumper to select bus CV operation: lower = normal (non-inverted), upper = inverted, not installed = no connection.
  • Channel 2— Three-position switch for Channel 2 input selection: left (−), center (off), right (+).
  • SW1— Three-position switch for Channel 1 input selection: left (−), center (off), right (+).
  • SW2— Three-position switch for Channel 2 input selection: left (−), center (off), right (+).
  • SW3— Three-position switch for Channel 3 input selection: left (−), center (off), right (+).
  • SW4— Three-position switch for Channel 4 input selection: left (−), center (off), right (+).
  • BU1 Input— Audio/CV input for Channel 1
  • BU2 Input— Audio/CV input for Channel 2 (switches to +1.000V when empty)
  • BU3 Input— Audio/CV input for Channel 3
  • BU4 Input— Audio/CV input for Channel 4
  • Bus CV— Bus control voltage output

How-To Guides

  • Calibrate Overall Amplification (P1)
  • Calibrate Octave Reference (P2)
  • Merging Two Pitch CVs for Chord Offset
  • Live Octave Transposition via Switch
  • CV Subtraction for Detuning or Difference Signals
  • Integrating Bus MIDI Pitch CV into a Patch
  • Static Chord Offset for Three Oscillators
  • Mirroring CV for Complementary Modulation
  • Manual Semitone Transposition Stack

Explore the interactive A-185-2 Precision Adder / Bus Access panel on BleepDex — tap any control to learn what it does.

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