A series of three polyphonic analog synthesizers released by Roland between 1978 and 1984. The first of the trio was the Jupiter-4, released in 1978. This was a transitional synth from Roland; it was their first polyphonic synth (4 voices), their first microprocessor-controlled synth, and their first synth with patch memory (a whopping 8 user-writeable memory locations). It retained the organ-like patch selection buttons underneath the front edge of the keyboard, in the manner of Roland's early monophonic synths, and the controls resembled the ones used on the System 100.
The Jupiter-8 was introduced in 1981. With 8 voices, two VCOs per voice, and a generous selection of modulation options (for a synth of its time), it was regarded as the flagship of Roland's line. It was one of Roland's first synths to primarily use sliders instead of knobs for parameter values, and the logical way the controls were laid out and grouped set a standard that Roland would continue to follow for years afterward. It was especially noted for the rainbow-colored row of pushbutton switches across the middle of the panel, the colors representing different function groupings. It was also a quite stable and reliable synth for its day. The Jupiter-8 was particularly noted for its ability to produce lush pads and smooth bass tones. Today, it is one of the most sought-after synths on the collector's market, with examples in good condition going in excess of $4000 US. Research into serial numbers by contributors at Vintage Synth Explorer indicate that about 3200 were produced.
Early production Jupiter-8s used a 12-bit DAC. This lacked sufficient resolution for proper VCO control, and some users reported tuning problems. The circuit was redesigned to use a 14-bit DAC, which solved the tuning issue and had other benefits in improving resolution of stored parameters. The last 400 or so Jupiter-8s produced came from the factory with a DCB interface, and a retrofit kit was offered that could add the interface to any unit with the 14-bit DAC. As DCB-to-MIDI converters are widely available now, any of these units can be adapted to MIDI.
This was followed by the Jupiter-6, an attempt to create a lower-cost version of the Jupiter-8. The two previous synths had relied on semi-integrated circuitry using opamps and OTAs from International Rectifier (the IR3109 and related parts), but to cut costs on the 6, Roland went with a higher level of integration using ICs from Curtis. This gave it a somewhat different sound than its predecessors; it didn't sound like the Jupiter-8, and some performers who bought it expecting a six-voice verison of the 8 were disappointed. And it didn't succeed in lowering the price enough to compete with the lower-cost polysynths being offered by Korg and Yamaha at the time. The lessons learned from this went into creating the Juno series. The Jupiter-6 remains somewhat controversial among collectors, with some Roland aficianodos avoiding it, and others considering it one of Roland's best analog synths.
In 2011, Roland introduced the Jupiter-80, a digital synthesizer based on the Fantom sound engine. Circuit-wise, it has nothing in common with the classic Jupiters, although it does emulate some of their functions. Reviews have been mixed. In 2013, Roland introduced a less expensive version, the Jupiter-50.