A voltage controlled oscillator on a chip, produced by Curtis Electromusic. It was widely used in early-to-mid-'80s polyphonic synths, including the Oberheim OB-8, Memorymoog and the Roland Jupiter-6. The 3340 simultaneously provided triangle, sawtooth, and pulse waveforms, the latter with pulse width modulation. Two frequency control inputs were provided: a volt-per-octave input with an internal exponential converter having adjustable scaling, and a linear input for frequency modulation. Soft sync and hard sync inputs were also provided. Built-in temperature compensation helped keep it in tune.

The 3340 was highly regarded for the quality of its sound. It was unusual among VCO designs in that it employed a triangle core. There are some rumors that the 3340s used in the Memorymoog was a slightly different design, and only certain ones will work in that synth.

Like nearly all CEM ICs, the 3340 is now very rare. Although Doepfer has produced a modular VCO which requires a 3340 (the A-111), they should not be used in new designs.

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