A-143-9 Voltage Controlled Quadrature LFO/VCO

The A-143-9 Voltage Controlled Quadrature LFO / VCO is a voltage controlled sine wave generator that produces a very clean sine wave signal. With approx. 3 kHz, the LFO reaches into the audio range, with an additional control voltage it can even be used as a VCO up to approx. 20 kHz.

A very clean sine signal from the A-143-9.

Compared to “real” oscillators like the A-110-1, it has a few limitations in addition to the smaller tonal range: No temperature compensation and a less exact 1 V / octave characteristic for control.

The same signal is available at the four outputs, each shifted by 1/4 oscillation (or 90 degrees), so that the first and third (or the second and fourth) outputs each supply an inverted signal.

User interface







Together we are strong

The A-132-2 Quad VCA I was a good complement to the A-143-9 when the amplitudes of all four outputs should be controlled synchronously. If the two modules are connected to each other on the boards using a ribbon cable (supplied with the A-132-2 VCA), the inputs of the Quad VCA are pre-assigned to the outputs of the Quadrature LFO. Unfortunately, the A-132-2 is no longer available, the otherwise extremely flexible alternative A-135-2 does not have the simple connection option using a ribbon cable but instead individual and mixed outputs, individual control voltages etc.

Crossfading and modulation

In connection with an A-132-3 dual linear/exponential VCA and a mixer, interesting crossfade effects can be created with simultaneous – phase-shifted – modulation of the audio signals.

An unusual “vibrato” that starts again and again. If the “Gain” and “CV” settings on the amplifiers are skilfully adjusted, a slight counter-vibration of the two VCOs can also be heard.


The Quadrature VCO A-110-4 is an interesting variant of this oscillator. Doepfer has also given it temperature compensation and the option of “Thru Zero” frequency modulation. The inverted sine and cosine outputs have been saved for this, but they can be generated by two simple inverters if required.

Technical specifications

Width8 HP
Depth50 mm
Power requirements30 mA (+12V) / -30 mA (-12V)