Roland Jupiter-4

Roland Jupiter-4

Roland Jupiter-4 Compuphonic
Manufacturer Roland
Dates 1978 - 1981
Price US$2,895
UK£1,810
JP¥385,000
Technical specifications
Polyphony 4 voices
Timbrality Monotimbral
Oscillator 1 VCO + 1 sub-oscillator per voice
LFO 1 triangle/square/sawtooth/reverse sawtooth
Synthesis type Analog Subtractive
Filter 1 resonant lowpass, 1 highpass
Attenuator 2 ADSR
Aftertouch expression No
Velocity expression No
Storage memory 10 presets/8 user patches
Effects chorus
Input/output
Keyboard 49 keys
External control None

The Roland Jupiter-4 (JP-4) was an analog synthesizer manufactured by the Roland Corporation between 1978 and 1981. It was notable as the company's first self-contained polyphonic synthesizer, and for containing digital control of analog circuits (termed "Compuphonic" by Roland), allowing for such features as programmable memories and voice assignment modes.

Priced at US$2,895, it was cheaper than polyphonic machines from its competitors (such as the Sequential Circuits Prophet-5 and the Oberheim OB-X). However, it did not sell well in comparison. (These poor fortunes were reversed on the release of its successor model in 1981, the popular Jupiter-8.)

Architecture

The four voice cards

The Jupiter-4's basic architecture consisted of four identical voice cards, each with a VCO (and sub-oscillator), resonant low pass VCF (Roland BA662 in earlier revisions or IR3109 in later models IC, which could self-oscillate), and variable-gain amplifier (VCA). Modulation included an Attack-Decay-Sustain-Release (ADSR) envelope for the filter, and another for the voltage-control amplifier and a final level output with an overload LED, as well as a separate unmemorized master volume control. The filter ADSR could be inverted, allowing for "upside down" modulation. The final VCA level setting could be memorized in user presets, and was prior to the overall master stereo output volume. 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. Those settings were memorized in the user presets but a fully adjustable depth remained independently configurable through the pitch wheel to combinations of VCO, VCF and VCA, as well as a bend range. The VCOs can garner unstable tuning if aging or low-quality electrolytic capacitors are used (two for each voice card). Synthesizer repair shops can replace these tuning capacitors with stable polystyrene capacitors for an instant perfect tune. Individual oscillator card VCO tuning is accessed by four capped holes in the middle of the back of the case, but the unit should be allowed to warm up before adjusting for at least 20 to 40 minutes prior to adjustment.

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:[1]

The final signal path also included a simple high-pass filter and a lush stereo chorus effect based on two, now rare, MN3004 ICs. The chorus circuit board is located underneath the modulation wheel, and has one control: a front button for enabling/disabling the effect. It is lush and wide, supplying a pseudo stereo effect when both outputs are used. This filter, as well as other parts of the machine, also use the BA662 VCA chips, which are also rare. Despite evidence against its alleged sonic magic, the BA662 remains sought by many x0xb0x builders, a superior clone DIY kit of the Roland TB-303. Numerous such chips are used in the early JP-4 circuits and the Roland TB-303.

The Jupiter 4 had ten preset sounds and also featured eight memory locations for user-created patches. Saving to those locations requires two widely separated write record buttons to be held, to protect against accidental writing. A battery located deep between the chorus and power supply preserves the contents of the memory ICs.

A quirk that catches many first-time users is that the lower right preset and user memory buttons disengage most programmable controls to the right of the arpeggiator section when a user or factory preset is used. The controls to the right of the arpeggiator are only live when the yellow manual button is selected. The controls are analog switches and potentiometers, but do not adjust the synth cards directly. They are supplied with hi/low logic voltages or 0–5 volt voltages. Multiplexers and analog to digital converters read the settings, then send them in digital form to the CPU. The CPU then converts these parameters to analog control voltages, and sends them to the analog voice cards and envelope gates. It is a remarkably stable hybrid pioneer with a great analog sound.

Despite not being incredibly popular, it did 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 eulogized that despite its limitations "the Jupiter 4 will be tatooed on my heart for ever".

Promars

In 1979, Roland released a two-oscillator monophonic synthesizer called the Promars, which is often considered a monophonic version of the Jupiter-4. The Promars did not have the Jupiter-4's arpeggiator or its "ensemble" chorus effect, and reduced the four voice cards to two with basic detune. It had the memory and preset selection buttons above the keyboard, which were less clumsy to use than those on the Jupiter-4. It also had 37 keys, making slightly smaller than the Jupiter-4.

The Promars was used by Depeche Mode (around early-mid 1982), Vangelis (early/mid 1980s), The Enid, Jethro Tull, Landscape and Spandau Ballet (synth lead on 'To Cut a Long Story Short').

Io MIDI retrofit kit

The CPU replacement for the Jupiter-4 by Covariance
Covariance's assigner board add-on

László Kővári aka "Covariance" developed a MIDI kit and CPU replacement for the Jupiter-4. This two-part kit expands the Jupiter-4's patch memory from eight to sixty-four and also allows recalled patches to be dynamically modified (the original 8048 disallows editing once the patch has been saved). In addition to MIDI all sliders and switches can receive MIDI control messages, the arpeggio can be synced to the MIDI clock as well. A second LFO was also added which is even faster than the Jupiter-4's original LFO.

The retrofit kit was named Io to reference to Jupiter's moon, and Input-Output.[2]

Notable musicians/bands known to have used the Jupiter-4

See also

References

  1. ↑ Gordon Reid (November 2004). "The History Of Roland, Part 1: 1930-1978". The History Of Roland. Sound On Sound Magazine. Retrieved 29 November 2010.
  2. ↑ Covariance (2010). "What is Io". MIDIpolis FAQ. MIDIpolis. Retrieved 9 December 2012.
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