A-110-4 is a so-called Thru Zero Quadrature VCO. The term "quadrature" means in this connection that the oscillator outputs sine and cosine waveforms simultaneously. The term "Thru-Zero" means that even "negative" frequencies are generated. But this a bit a misleading term as negative frequencies do not really exist. "Negative" means in this connection simply that the sine/cosine waves will stop when the linear control voltage reaches 0V and continue with the opposite direction as the linear control voltage becomes negative and vice versa.

Linear modulation by another oscillator using the thru zero feature generates audio spectra than cannot be obtained from an oscillator without the thru zero function. The reason is that a "normal" VCO will simply stop as the linear control voltage becomes zero or negative. But a thru zero VCO will start again with "negative" frequencies as the the linear control voltage becomes negative.

The main advantage of the A-110-4 compared to other Thru Zero VCOs is that the design uses a sine/cosine core. The sine/cosine waves are not derived from other waveforms (e.g. sawtooth or triangle) by means of waveshaping. Rather the sine and cosine waves are the core of the VCO which results in very pure waves with a minimum of distortion and overtones.

Features

• Thru Zero Linear Frequency Modulation in Analog Format!
• Quadrature outputs, 180 degress out of phase
• 1V/Oct pitch CV input
• Exponential and Linear Frequency Modulation in puts with dedicated attenuators