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.
