Doepfer A-185-2 Eurorack Precision Control Voltage Adder Module
Doepfer A-185-2 - Precision CV Adder
Doepfer's A-185-2 is a precision control voltage adder / buffer. Precision means that the amplification of the inputs with attenuators is exactly 1.00 and is suitable to add control voltages for the pitch control of VCOs (e.g. from a keyboard + sequencer 1 + sequencer 2). Summing resistors matched to 0.1% are used to obtain an accuracy of 0.1% for the added voltages.
The module is equipped with four CV inputs: one with attenuator and three without attenuator. Each input is normalled to +1V (i.e. if no plug is inserted the input contributes 1V to the sum appearing at the output).
The input with attenuator can be used for common modulations (e.g. from an LFO, ADSR, Theremin, Pitch-Bender) for all VCOs connected to the output. The Lev. 1 control is used to adjust the depth of the modulation, the first switch selects the polarity of the modulation. If not signal is connected to the first socket the attenuator works as a (fine) tunig knob because a voltage in the range 0... +1V (left position of the switch) is added to the CV output.
The inputs without attenuators are planned to add control voltages coming out of keyboards, sequencers, MIDI-to-CV interfaces, ribbon controllers or other CV sources that follow the 1V/Oct standard. For example the CV of a keyboard can be used to transpose the CV coming from a sequencer, or the CV of a slow sequencer can be used to transpose the CV of a fast sequencer.
Each input is equipped with a three-position switch that determines if the corresponding voltage is added (right position), subtracted (left position) or if the input has no effect (centre position). If no plug is inserted the corresponding switch works as an octave switch for the lower three sections as the default 1V are added or subtracted to the output voltage according to the switch position. The first switch can be used to add a variable voltage to the sum output. The variable voltage is adusted with Lev. 1 control and the knob works then as a kind of a (fine) tuning control.
The module is equipped with 4 outputs: three non-inverting and one inverting output. An internal jumper can be used to connect the non-inverted or inverted output to the CV line of the A-100 bus. That way the module can be used to control several VCOs that are connected to the same bus board as the A-185-2