Doepfer A-143-9 Voltage Controlled Quadtrature LFO/VCO Eurorack Module

Module A-143-9 is a derivative of our planned thru-zero quadrature VCO. It is a voltage controlled sine LFO with 4 outputs. The phase shift between the outputs is 90 degrees. The sine shifted by 90 degrees is also called cosine, the sine shifted by 180 degrees is nothing but the inverted sine, and the sine by 90 degrees is nothing but the inverted cosine.

The frequency range is from some minutes to frequencies beyond audio with three ranges selected by a toggle switch:

• switch position H: about 30 Hz ... 3.5 kHz with the manual frequency control ("Frq."), beyond 20 kHz with additional external CV
• switch position M: about 1 Hz ... 150 Hz with the manual frequency control ("Frq.")
• switch position L: about 0,1 Hz ... 10 Hz with the manual frequency control ("Frq."), down to several minutes with additional external CV

Two exponential frequency control inputs are available: CV1 without attenuator and CV2 with polarizer. Consequently the module can be used even as an experimental sine VCO but does not feature an exact 1V/oct CV input! The precision CV input will be left to the thru-zero quadrature VCO.

Two LEDs display the positive and negative share of the sine output.

The core of the module is a so-called quadrature circuit that generates a sine a cosine signal with very low distortion. The quality of the sine/cosine signals are much better than those generated by a waveform converter with a sawtooth or triangle signal as starting point.

The output levels are about 5 Vss (+/-2.5V) but can be adjusted internally by a trimming potentiometer (P5 "Shape").

Typical applications:

• External sine/cosine oscillator for the frequency shifter or
• Modulations with pure sine/cosine waveforms
• quadrature/barberpole effects (e.g. with the voltage controlled mixer )
• experimental sine/cosine VCO (e.g. for FM sounds)

Many users suggested to add a common output level control, i.e. four VCAs with one common control (manual + CV without attenuator + CV with polarizer) for the output levels. This is why we also designed the Quad VCA module with the possibility of an internal default connection to the four outputs of the A-143-9 (no soldering required, short 10 pin flat cable with removable connectors on both ends).

The A-143-9 is also a meaningful addition for the Frequency Shifter modules or . It enables frequency shifting even below 50 Hz generating e.g. these mellow beat sounds with a few Hz frequency shifting only. The following document describes how to connect the old A-126 and the : . The new Frequency Shifter has sockets at the front panel available.

The thru zero version of the A-143-9 with temperature compensation is the module .