Roland Jupiter-4 - Architecture

Architecture

The Jupiter 4's basic architecture was 4 identical voice cards, each with a VCO (with sub-oscillator), resonant low pass VCF (Roland IR3109 IC, which could self-oscillate), and VCA. Modulation included an ADSR envelope and LFO. The LFO, routable to oscillator pitch, pulse width, filter cutoff and amplifier, was notable for being able to reach audio frequencies, allowing for crude FM and AM synthesis.

The Jupiter 4's two most distinctive features were provided by virtue of its "compuphonic" digital control of the four voice cards, made possible by two Intel 8048 chips:

• An arpeggiator, with a choice of up, down, up/down, or random mode. The arpeggiator can be prominently heard in Duran Duran's 1982 hit single "Rio."
• Four voice assignment modes, which, as well as simple 1 VCO-per-voice polyphony, included the ability to effect 4-VCO unison when one key was pressed, 2-VCOs per voice when two keys were pressed, and 1-VCO per voice when three or four keys were pressed. This effect can be heard on tracks such as "Seconds" by The Human League and "I Dream of Wires" by Gary Numan.

The final signal path also included a simple high pass filter and a stereo chorus effect. The Jupiter 4 had 10 preset sounds and also featured 8 memory locations for user-created patches.

Despite not being incredibly popular, it did manage to find its way into the hands of some musicians, most of which were associated with the New Wave and synthpop music scenes (see below). Phil Oakey of The Human League eulogised that despite its limitations "the Jupiter 4 will be tatooed on my heart for ever".