Roland JX-10

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Roland JX-10 (or Super JX)
Manufactured by Roland
Dates 1986-1989
Price US$2195
Technical specifications
Polyphony 12 voices in 'WHOLE' and 'SPLIT' mode, 6 voices in 'DUAL' mode
Timbrality 2 ('SPLIT'/'DUAL' modes)
Oscillator 2 [DCO]s per voice/4 in 'DUAL' mode. Waveforms: SAW/SQUARE/FIXED PULSE/NOISE. Oscillator sync, xmod.
LFO 1 sine/square/random=noise with delay and rate
Synthesis type Analog Subtractive
Attenuator 2 ADSR Envelopes/4 in 'DUAL' Mode. They both have 3 levesl (and '0') of "Key Follow"
Aftertouch Yes
Velocity sensitive Yes
Memory 50 preset tones/50 user tones/64 patches, optional M64C memory cardtridges holding 50 tones
Effects chorus, delay ('chase play' using voices, not a 'real' delay FX)
Keyboard 76 keys
Left-hand control Pitch bend Lever with upward moving controlling LFO
External control MIDI for playing notes/PG-800 programmer for sound editing

The Roland JX-10 (also known as the Roland Super JX) was a 12-voice analog synthesizer keyboard produced from 1986 to 1989, along with a rack-mounted version, the MKS-70. It was the last true analog synthesizer made by Roland and has been critically acclaimed as one of their classic analog instruments. The design is essentially two Roland JX-8P synthesizers put together, with a 76-note velocity-sensitive keyboard with aftertouch. It also includes features not found on the JX-8P, including a simple 1-track sketchbook sequencer and a delay effect (which works like a "MIDI delay" by delaying one tone rather than acting as a true DSP delay effect). However, the JX-10 is not exactly the same as "two JX-8P's" because the chorus is not identical to the JX-8P (hence the chorus sounds different between the JX-8P and the JX-10 with single patches). The JX-10 also has a slightly different amplifier section as well as different electronic components which further distinguish its sound from its predecessor, the JX-8P.


Like most synthesizers of the time, the JX-10 is programmed by selecting a parameter through a small keypad and editing the parameter using a data wheel (which Roland dubbed the "alpha-dial"). Like the JX-8P, this can be bypassed by connecting a PG-800 programmer to the synthesizer. The PG-800 connects to a specific PG-800 port on the back of the synthesiser. Alternatively the JX-10 and MKS-70 can be programmed over MIDI using a controller device such as the KiwiTechnics Patch Editor (a firmware update is required on the JX-10).

Factory Presets[edit]

The JX-10 and MKS-70's factory presets were created by Eric Persing and Dan DeSousa.

Playing Modes[edit]

The JX-10 combines two completely separate 6-voice Tone Modules (A-Upper and B-Lower) which allow it to function as a single 12-voice synthesizer or as two 6-voice synths capable of layering or splitting two different Tones simultaneously. There are six playing modes:

  • Dual Mode - layers sounds from both Tone modules which can be balanced
  • Split Mode - allows for split-keyboard play of the Tone modules, upper and lower sections can overlap
  • Whole A - Upper Tone Module controls all 12 voices
  • Whole B - Lower Tone Module controls all 12 voices
  • Touch Voice Mode - adds velocity switching
  • Cross-Fade Mode - controlled by the amount of velocity, one tone fades in while the other tone fades out


The JX-10 has space for 64 patches in its internal memory, each of which can be composed with one (12-voice) or two tones (rendering the synth 6-voice polyphonic). These tones can be selected individually, combined together, or split. Of the 100 available tones, 50 of them can be edited and saved to memory; the other 50 are factory patches. The JX-10's memory can also be expanded by plugging in a M-16C, M-32C (very rare, originally only available on the Japanese market) or M-64C memory cartridge. If a cartridge is inserted, the JX-10's built in sketchbook sequencer can be used (it can only be used if a cartridge is present). The JX-10 / MKS-70 can also read and write tone data for the JX-8P this way (which in turn can only use the M-16C). The M-64C can store 64 patches and 100 tones; the M-16C can store 32 tones only (no patches).

MIDI Implementation[edit]

The MIDI implementation on the JX-10 is somewhat faulty and lacks common features. Most importantly it cannot send or receive Tone or Patches by MIDI SysEx. The MKS-70 (rack version of the JX-10) does however send and receive tones and patches over SysEx because it has different firmware in EPROM. If the firmware in the JX-10 is updated then it will support SysEx.
It can also be noted that the JX-10 transmits MIDI Control Change 123 (all notes off) instead of "normal" MIDI Note-Off messages every time a key is released (apparently the JX-8P does this as well). This can be filtered out by editing CC 123 in the sequencer if it should create any problems; normally it does not.


The JX-10 also has a 2U rack-mounted counterpart called the MKS-70. It is basically the same as the JX-10, except that the MKS-70's tones can be edited through MIDI using SysEx (this can be rectified on the JX-10, see below).


The JX-8, JX-10 and the MKS-70 use vacuum fluorescent displays which give the instruments their characteristic green/blue glowing read-out. In some cases these displays can fail with age, displaying 888888888888 or having other issues. One cause of these problems is the corrosion of a small coil component in the display driver circuit. While Roland used similar displays across a number of products at this time, interchangeability of displays between products is limited. Replacement parts are scarce and some experimenters have replaced the vacuum display with an LCD device and supporting circuitry. In January 2014 a custom supply of new coils became available for the JX-8/JX-10 and the MKS-70.

Firmware and CPU Update[edit]

Colin Fraser has released a modified firmware for the Roland JX-10 only which adds SysEx editing of tone parameters via MIDI (the standard Roland firmware for the JX-10 did not support editing over MIDI; the MKS-70 does). Fortunately, an update is fairly easy and does not include desoldering of the old EPROM chip (a 32k 27C256) since it is easily detachable from its socket on the assigner board.

As of June 2014 Colin announced he will stop selling the modified firmware due to the works of Frederic Vecoven and his newly written firmware upgrade for the Roland JX-10 whom's MIDI implementation not only is rewritten from scratch but also surpasses Colin's version in the means of assignability since it contains the same SysEx implementation along with added functionality.

As Colin stated: "I have decided therefore to stop selling my JX ROM. It would be daft to go to the bother of upgrading your ROM, and not getting the extra features of Fred's ROM for the reasonable extra cost."

In March 2013, a request was made on the GearSlutz electronic music forum for beta testers to test a new version of the Roland MKS-70 firmware. The replacement firmware adds features to both JX-10 and MKS-70 instruments, including faster envelopes and a new MIDI implementation. Two versions of the firmware are in development: for the full upgrade, CPU replacement (Intel 8031 to 80C320) is required on the two sound boards, and three new EPROMs.

Notable Users[edit]

External Links[edit]