doepfer a-167 analog comparator / subtractor / offset generator price : $75.00

a-167 is a module that compares analog voltages and derives a gate signal. the state of the gate output (low/high) depends upon which of the voltages is higher. it is possible to compare two external voltages (+in and -in) or an external voltage (+in or -in) with a manually adjustable value (offs. control). both analog inputs +in and -in are equipped with an attenuator. internally the module generates the voltage k1*(+in) - k2*(-in)  + offset and und sets or resets the gate output depending on the result of this internal voltage (>0v or <0v). the factors k1 and k2 represent the manual attenuators. a led shows the current state of the gate output.

the gap control is used to adjust a so-called "hysteresis". as long as this control is set to zero the switching levels for both on and off state of the gate signal are identical. as soon as the gap control is turned up the switching levels for on and off state fall apart and a so-called hysteresis appears. the sketch at the bottom of this page shows the gap function.



normal and inverted gate outputs are available. in addition the internal voltage k1*(+in) - k2*(-in)  + offset is available at the analog sum socket. consequently the module can be used as subtractor and offset generator too.

applications: generation of gate signals depending upon analog voltages. e.g. a gate signal that depends upon the present value of a lfo (triangle), adsr or random signal can be generated and used to control a voltage controlled switch that on the other hand switches different control voltages or audio signals. the module can even be used to add the free-running mode to each adsr ,e.g. a-140 similar to a lfo but with separate controls for rising and falling edge and exponential waveforms - in contrast to the linear waveforms of a lfo.



this patch shows an "adsr-lfo" that is gated with the gate input of the a-140, i.e. the "lfo" works only if the gate input is "high". waveform and frequency are controlled by the controls attack, decay, sustain, release, offset and +in. the gap setting has no function. attention: only certain settings of the controls create an adsr-lfo!



or this patch of an "adsr-lfo" the controls attack, release, offset, gap and +in determine the waveform and frequency. decay and sustain have no function. attention: only certain settings of the controls create an adsr-lfo!



this module has a maximum current draw of 20ma. it requires 8 te/hp worth of space to fit in a eurorack frame.

to view this module's user manual as a pdf file, please click here.