Roland JX-8P (1984)

Roland JX8P

 
UNDER THE HOOD
Inside Roland JX-8P

Inside Roland JX-8P

Inside Roland JX-8P

Inside Roland JX-8P

 
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NEC D8253C2 NEC 8155HC HITACHI HD63803 HITACHI HD14066BP SHARP IR94558      
 
IMPRESSION

Another Roland analog synth, and this one is described as « Hybrid ». This one has been the last analog synth, moreover, because the « D » series will take over with the advent of totally digital synths. The D-50 will eventually be the best known in that series.
The JX-8P is a very nice synth, having some futuristic look, a vacuum tube using a fluorescent display, rather than the classic LCD screen. The machine is quite heavy too and one senses a certain notion of robustness. His nickname « hybrid » comes from that capability to use a ring modulation. This is a synchronization process between the two oscillators. Rather than deliver their signals independently to the mixer, they may use the « FM » method of the synths of the series « DX » of Yamaha, and it is thus the oscillator1 that will inject Its signal in the oscillator 2. Once out from this modulation stage, the waveform will be profoundly modified, depending the volumes applied on two oscillators, and so we can produce some complex waveforms like JX8P’s competitor # 1: The famous Yamha DX-7 . However the DX-7 uses 6 oscillators that are wired according to 32 possible algorithms … So the JX8P is largely dominated in this very specific field …However, it is possible to create some quite realistic « Big Ben » bell sounds, or metal sounds typical of FM synthesis. Obviously we can choose to create purely analog sounds as well. The JX8P has more parameters than the Juno and Alpha-Juno series.

In fact I often compare it to a Jupiter-8 having the MIDI connections, but without the split or arpeggiator features. This says, nothing is more indicated than a sequencer to generate arpeggios, so it is not a worry. The « split » mode would have been interesting on this keyboard given its 5 octaves. On the other hand we have the unison mode (like on the Jupiter-8), which will make it possible to play 12 oscillators per note, which will result in an extremely rich and thick sound.

Indeed we have two oscillators (DCO) available per note, and also 2 envelopes. Thus allowing to have a dedicated envelope for the control of the volume amplitude, and the other envelope to control the filter. There are a lot of parameters that control the dynamics of the keyboard (and the aftertouch for that matter, but this one requires a strong hand to control its nuances to say the least). The programming interface is standard. A function / parameter number is entered, and then a value is entered, as on the majority of the synthesizers of this era. If you want to remember the good old days of the orders assigned to real-time controllers, you will have to join the services of the programmer « PG-800 ».

The sound produced by the JX8P has always amazed me in the negative sense of the term. It sounds quite thin, with a too pronounced medium frequencies spectrum, very dry and shiny. Whatever may be done to mitigate its effect, a brilliant aspect is heard. In addition, the adjustment range of certain parameters leaves doubtful. For instance (I specify that this is an example and I exaggerate things to highlight them) a value from 00 to 80 doesn’t seem to have an impact on a parameter. Then, set to 81 he reacts a little. But set to 85 he reacts infinitely too much. From 85 to 99 the nuance is no longer felt … So we end up with an « audible » value having an effect on the sound from 81 to 85 … While we have a range from 00 to 99 … Quite weird therefore … This applies to several parameters of this synth, like the enveloppe for instance. Of course I will be told that my model should probably have some issues, But I would say that I had the opportunity to do the same experimentation on two other JX8P, one of which had the PG-800 programmer and I concluded to exactly the same phenomenons.

Despite everything, it seems to me suitable for some electro bass, strings-synths, and aggressive leads. Indeed this synth proposes a rather punchy sound. The sound is not « thick » or « gloomy » like the Alpha Juno 1. It is much more regular, almost digital and therefore pretty thin. When you try very soft pads, you get a feeling of shortness of breath and frequency completely « eaten » by the filter, making the sound a bit « saturated », which is really surprising since the circuit handling the filter is an IR3R05 like used on other Roland synths of the same era and which do not give this impression … We could believe that this circuit is combined with some others and may end up by deeply modifying the characteristics of this filter …

It has a very good MIDI implementation, which will allow with a sequencer to control it precisely. It also has( like the Junos) a quite reduced polyphony of 6 notes, but it never really disturbed me. You can achieve pretty good things by playing in very low keys, with slightly distorted sounds, one can then approach big mythical syntheses in the sound impression.

A small tour into the guts of this imposing machine reveals the classic I.C. brand Roland for the audio part. Note that the motherboard of this synth is particularly fullfiled, and especially the section « cpu / logic board ». I often wondered why there were so many programmable timers and other microcontrollers, whereas compared to the Alpha Juno 1 released a year later, there is nothing more Which would require such a debauchery of logic circuits … But I suppose the engineers of Roland had good reasons …. Let the specialists debate about that. The 6 oscillators seem to be built from Quadruple Analog Switch (SPST) Multiplexer circuits.
On the motherboard we find :

  • 12x HITACHI HD14066BP (DCO probablement)
  • 14x SHARP IR94558 Dual-Op Amplifier
  • 6x IR3105 (VCF/VCA)
  • 2x MN3009/MN3101 BBD (Chorus)
  • 1x NEC D8049C (Timer controler)
  • 4x NEC D8253C-2 (Programmable Timer)
  • 1x HITACHI HD6308 (CPU)