image courtesy of Kevin Lightner

The Jupiter-8 is an 8-voice polyphonic synthesizer with a 61-note (C-C) keyboard. Each voice consists of 2 VCOs. VCO1 is switchable between triangle, sawtooth, pulse, and square waves and can be switched between 4 octaves. VCO2 has the same options except the square wave is replaced by a noise generator switch and it has the same 4 octave range, with a switch to put it into "Low Frequency range". There is a simple mixer that balances the level of the two oscillators. There is a single slider to control the amount of cross-modulation of VCO-1 by VCO-2. Pulse Width Modulation (PWM) is set by a slider to set the level of modulation, and then a switch to select between LFO, ENV-1, or manual PWM. The Jupiter-8 also allows VCO1 to be synced to VCO2. Either or both VCOs can be modulated by either or both of the LFO and ENV1. The LFO features controls for rate, delay, and four waveforms, sine, saw, square, and random (sample-and-hold). LFO2 is triggered by a big white button next to the pitchbend/modulation lever. It is controlled by two switches and two sliders. The switches enable the modulation of the VCO and the VCF and the sliders control the amount of modulation for each destination.

The Jupiter-8 voice has two filters. In addition to its lowpass, resonant VCF it has an adjustable, non-resonant, and non-modulatable highpass filter. Whereas the highpass filter is set by a single slider, the lowpass VCF is much more flexible. The VCF has a switch to choose between 2-pole (12 dB/octave) and 4-pole (24 dB/octave), as well as controls for frequency level and resonance. The VCF can be modulated by one of the envelopes, the LFO, and keyboard tracking, with sliders adjusting the amount of modulation for each of these three sources.

Both envelopes (ENV1 and ENV2) are ADSR (Attack Decay Sustain Release). Key follow may be switched on and off for each envelope. ENV1 can be set to normal or negative polarity. ENV2 is hardwired to control the VCA, with a slider controlling the amount. The bender can affect pitch and/or filter cutoff, each of which has a slider for amount. VCO1 and VCO2 have separate on/off switches for bender modulation. There is also a "wide" bending option, which scales the bender to extreme ranges.

The Jupiter-8's memory can hold 64 patches and 8 "patch presets." Patch presets can store keyboard splits, along with the settings for the arpeggiator, voice assign mode, hold, portamento, as well as many of the modulation settings. The Jupiter-8 features keyboard split or layer. Split allows you to assign a patch to 4 voices above the split key and a patch to the 4 voices below it. Dual creates a keyboard with 4-voice polyphony, having two voices playing separate patches for each note. The balance between both patches in split or a dual mode is controlled by a slider. The arpeggiator is switchable between 1, 2, 3, and 4 octaves and four modes: up, down, up and down, or random. In split mode it works on only the lower split. There is a knob for portamento in the mod section (to the left of the keyboard). It can be switched to off, on and upper only. The Jupiter 8 offers Solo, Unison, Poly 1, and Poly 2 modes. Solo allows you to only play one voice at a time (ie. one 2-oscillator voice). Unison mode plays all of the voices, all of the time, dividing them as evenly as possible between all sounding notes. That means that if you played a single note, you would hear all 8 voices stacked together. Playing two notes would get 4 voices apiece, playing three notes would get 3 voices on the first two notes and 2 voices on the third, playing four notes would get 2 voices apiece, and so on. This offers the flexibility of having a polyphonic keyboard when you need it and the ability to get a fatter sound out of one or two notes. Poly 1 is the normal 8-voice polyphonic mode, and Poly 2 uses normal polyphonic allocation as long as you play legato. Once you lift your hand off the keyboard, any new notes will cut off the releases of all currently sounding notes. This is recommended for use with portamento. "Hold" is equivalent to the sustain pedal, but it is also a programmable parameter - that is, a sound in a Patch Preset can be permanently "held." Hold can be set for either or both sides of a split/layer. Modulation parameters include pitch bend sensitivity, VCO bend range (Wide, Normal, or Off for each of VCO1 and VCO2), aftertouch routing to either filter cutoff or vibrato (from LFO2), and aftertouch sensitivity.

The Jupiter-8 did not come with MIDI, although MIDI retrofit kits were made for it by third-party manufacturers. The Jupiter-8 features external input for control of the VCA and VCF and an input for syncing the arpeggiator to an external clock. The sync input can be set to control 8th notes, triplets, or sixteenth notes in the arpeggiator. There are two sets of 1/4" and balanced XLR outputs, one for each side of the split, or each patch in dual mode.

[information compiled from the archives at Hyperreal]