After a few years in the making, I’m delighted to announce that Nebula-X balanced outputs for the Roland JX-10 is finally here.
Soon after launching Nebula balanced outputs for the Roland MKS-70 back in Summer 2021, I received enquiries asking if I had plans to do something similar for the Roland JX-10. I took all those enquiries onboard and considered a replacement JX-10 jack-board with balanced outputs but the challenges were simply too much for me to pursue this kind of project at the time.
The JX-10 is a performance synthesiser. It has a lot more ports than the MKS-70. The JX-10 jack-board also hosts the programmer port and the headphone socket. Oh and one last thing, while I had three MKS-70s, I didn’t have a JX-10! 😒
I continued to receive enquiries and so a version of Nebula for the JX-10 remained in the back of my mind for a couple of years until I had an idea to potentially kill two birds with one stone.
Balanced lines drastically reduce noise between the outputs of one device and the inputs of another. In the JX-10 however, there’s an annoying noise source inside the actual keyboard. The audio connections between the voice-boards and the jack-board run straight underneath the very noisy display. Noise picked up by those lines was enough to make Roland use screened cables for those connections, something that wasn’t deemed necessary in the MKS-70, as the layout is quite different. If I could find a way to mitigate internal noise, that would give a replacement jack-board for the JX-10, something that would make a real difference.
So how was I going to achieve a better noise performance? Allow me to digress slightly to explain how this might be possible…
When I was a student in the early eighties and getting my first studio together, the lack of funds often pushed me into thinking outside the box. To reduce noise without balanced lines for example, I used something which I referred to as ‘quasi-differential’ transmission. My mixing desk had balanced inputs but most of my gear didn’t have balanced outputs. Normally, we’d just tie the inverting pin in the connector at the balanced input, to the screen (ground). If however, we use a screened 2-core cable and don’t join the inverted signal line to the screen, then the common rejection feature of the balanced input would remove noise as if the line was balanced… kind of. Using this principle was in my opinion, something worth experimenting with and suddenly Nebula-X balanced outputs for the Roland JX-10 looked like a worthwhile exercise.
You may have noticed that to do this trick, screened 2-core cables will be required. This can’t be done with screened single core cables. Those familiar with the insides of the JX-10 will be aware that the lines connecting the voice-boards to the jack-board, are screened single-core cables so YES, new cables will be required but don’t worry, I figured that these should be supplied with Nebula-X.
On top of that, while there’s a 4-pole connector on each end of the audio lines in a standard JX-10, the audio connections on Nebula-X are 6-pole as each voice-board connection will require two sets of signal, 0V and screen.
So how does this quasi-differential system work?
Well, we kind of use the second core in the cable, the core that's connected to ground at the voice-board and goes into the inverting input of one of Nebula-X's differential amplifiers, as bait. We actually want this core to pick up noise!
You see, both the signal carrying core and the 'second' core go into a differential amplifier with the former connected to the non-inverting input and the latter connected to the inverting input. The differential amplifier rejects, or filters all signals that are common on both inputs. The only common signal is of course, noise since noise hits everything in the same way and doesn't give two hoots if one line is inverting and another is non-inverting.
Do be warned however. A balanced line can NOT get rid of noise that's already in the source. Any noise generated on the voice-boards for example, won't be filtered out.
And YES, you’re absolutely correct; to implement my quasi-differential line trick, as well as having balanced outputs, Nebula-X also has balanced inputs. I actually used the INA2134 by Texas Instruments which is an insanely high-specification device.
NEBULA-X BALANCED OUTPUTS FOR THE ROLAND JX-10 PRE / POST NOISE TESTS
Of course, apart from wanting to satisfy my own curiosity, I don’t expect anyone to take my word for it. Although the theory is sound and indeed, I've used my quasi-differential system many times over the past few decades, I'm quite aware that my word might not be enough. So as soon as I can, I'll be posting some test results. Most likely in the form of a video, I'll record the outputs from my JX-10 with the original Roland jack-board and then with Nebula-X.
Other than having balanced inputs and a bunch of sockets that aren’t on the MKS-70 jack-board, Nebula-X inherits all the principles that I used on Nebula. Apart from fulfilling the main objective, Nebula-X has revised, more robust MIDI hardware, a MIDI LED indicator (to show MIDI IN) and socketed ICs allowing the user to easily change devices .
Removing the original jack-board can be a bit tricky but with a little patience, it’s not impossible. A long crosshead screwdriver with a long thin shaft is really helpful.
As mentioned, the original audio lines from the voice-boards going to the jack-board, need to be removed or at least disconnected at the voice-board ends as well as the jack-board end. The reason I mention the latter, is that I like my upgrades to be easily reversable. In fact, I absolutely hate the idea of upgrades or modifications that require permanently compromising beautiful vintage equipment and that’s why ALL my upgrades can easily be removed and equipment and respective gear returned to its factory condition.
As with Nebula, designing Nebula-X balanced outputs for the Roland JX-10, required a couple of workarounds which in my opinion, were acceptable compromises.
Roland implemented an ingenious switching system which allowed for automatic voice output selection, depending on which output sockets had jack plugs in them. Doing something similar with Nebula and Nebula-X was impossible for one reason and one reason only: space.
As per the original JX-10 jack-board, the pedal inputs on Nebula-X are also switched ‘stereo’ sockets. Being much wider than mono switched or stereo unswitched sockets, they simply wouldn’t fit in the locations of the output sockets.
As such, the level selector switch for the mono output has been replaced with a switch that changes the output configuration of Nebula-X from stereo to four independent outputs.
Finding a suitable switch was a challenge which began with the design of Nebula. Remember that the memory protection switch on the MKS-70 is on the front panel so I didn’t need an ON-OFF-ON switch. All I needed was an ON-OFF switch to energise a couple of relays.
On the JX-10 however, the memory protection switch is on the jack-board. Unfortunately, despite my best efforts, I couldn’t get an ON-OFF-ON version of that switch. 😡 Hence, the memory protection switch on Nebula-X doesn’t have a ‘centre off’ position.
Nebula balanced outputs for the Roland MKS-70 is supplied with a label which goes on the back of the instrument, to remind users of the switch position for stereo and individual outputs.
Similarly, Nebula-X will be supplied with two (smaller) labels for output mode select and memory protection ON / OFF.
One of my philosophies when considering a new design, is to follow the old 80% planning and 20% doing rule. The first thing to consider, is whether or not the new project a worthwhile venture. As mentioned at the start of this post, initially I wasn’t able to convince myself that Nebula-X was worth the hassle. Designing the electronics doesn’t start with a blank schematic. One needs to work out if the new peripheral or modification will work with the host system. Since there are very obvious similarities between the JX-10 and the MKS-70 and bearing in mind that Nebula for the MKS-70 already has a proven track record, it seemed that Nebula-X balanced outputs for the Roland JX-10 would theoretically work.
The mechanical aspects of of a design are also important. There's no point designing s cool bit of electronics if for example, it's not going to fit! In the case of Nebula-X, I wanted an easy drop-in design. That’s great but things like screw holes need to line up and sometimes that’s quite challenging when dealing with the types of tolerances in a machine that’s forty years old. Having said that, I do see machines like the Roland JX-10 in a slightly different light. It’s kind of amazing that Roland and other manufacturers was able to achieve such well-fitting panels with the technologies that were available in the eighties.
Indeed, it's not all about electronics. When making peripherals for other manufacturers' equipment, it's important that they should fit. Everything must line up perfectly. Nebula-X almost seems like it should always have been there!
Briefly touched on earlier, finding suitable sockets was another challenge. With no idea how many Nebula-X systems will be sold, I need to secure a source that will be reliable and offer me realistic prices.
All control port sockets like the two switch inputs, the pedal inputs and of course the programmer port, all function as they should.
Roland was keen that their instruments could be used live as well as in the studio so like the MKS-70, the JX-10 has a mono output that can be fed directly into an amplifier. I decided NOT to make this output balanced and set the output level to be compatible with most keyboard amps and combos... not that I imagine anyone taking their JX-10 down the pub for a Friday night gig!
Anyway, after all that, Nebula-X ended up fitting like a glove. It literally became a drop-in design exactly as I had intended and in my humble opinion, Nebula-X balanced outputs for the Roland JX-10 is an easy to install and worthwhile upgrade for the serious JX-10 user.
One last point; balanced outputs are 6dB hotter than their unbalanced counterparts. That can only be a good thing.