Module A-143-9 is a derivative of Doepfers 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 270 degrees is nothing but the inverted cosine. The frequency range is from some minutes to moderate audio (a few kHz) with three ranges selected by a toggle switch.

Two 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! 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 and 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.

Typical applications:

• External sine/cosine oscillator for the frequency shifter A-126
• Modulations with pure sine/cosine waveforms
• quadrature/barberpole effects
• experimental sine/cosine VCO