It’s alive (again)…
I really need to stop these “It’s alive” posts, but here’s another one. The Super JX boards arrived the other day and I finally got them on the bench last night. I struggled a bit with the display and Guy Wilkinson and Fred Vecoven helped me over email.
So today I went further and added more cables and emulated the volume board main volume control. Now I have sound.
Spent a few days building a proper front panel to control the assigner board and allow me to set parameters etc. I’ve now got that working (first time) and connected to the assigner board.
Hard to think I started this in July and it sort of fell by the wayside whilst I waited for sliders to arrive from AliExpress, first I bought 80 non 0.1” spacing sliders, so without drilling the perfboard they were not going in, so I ordered another 80 and this time they were 0.1” spacing. But again hesitant I did nothing with it, then I saw the new MPG-7X by retroaktiv and it had reduced the slider count by using buttons instead for some functions, now I had thought of this but now I had seen it I decided I had enough bournes LED sliders to build the editor.
I love all the stuff you make.
Though, do you ever sleep? 
I have to make the most of the little electricity we have each day.
Further updates, I’ve started mounting boards into a chassis.
I built up the switch mode replacement PSU for the super JX project. This replaces the transformer and huge PSU of the JX which would not fit into this project. As I’m using an OLED display I didn’t need the VFD power rails.
I moved the power connectors from the original power supply after testing the voltages of the new one.
this may be an obviously stupid question… does “complete” not include the case?
Complete innards, I didn’t want the case or keybed. I said the seller can flog the keys on ebay etc. It’s going into a 19” rack for an MKS-70 build.
So this has taken a back seat to a few other projects and updates, but I learned something interesting about the jx-10 and jx-8p synths, the voice boards are effectively a complete self contained 6 voice polysynth with a chorus. They simply take serial commands from the assigner which controls the display, keyboard, MIDI, inputs etc and front panel. It outputs serial commands for note on/off and all the parameters and the processor in the voice board does the work of creating sounds from that serial input.
So rather than attach my editor to the jx-10 assigner and over complicate matters, why not ditch the assigner, make my own front panel with just what I need and reduce the displays to 1 rather than 2. I can simply change all my midi output to the corresponding serial commands and talk directly to the boards.
I also worked out how to double the amount of MCP23017 chips I can have by using two i2c busses and modding the library to support both busses. The OLED display is now on a 3rd i2c buss and connected via an i2c back pack. This means I can remove the SPI display I was using for parameters and editor control. I have 11 MCP chips now to read in all the buttons and power the LEDs. I chopped out the old front panel and built a new one and removed the assigner.
One other thing is the assigner also generates +/-5.6v for the voice boards, these are derived from the +/-15v on the assigner so I need to build these regulator circuits, also the assigner generates an 8mhz clock source which I will get the Teensy to do and buffer it to +5v. I can now free up the assigner power cable and use that to supply all the power my controller/assigner needs.
Old board hacked out
New board installed keeping a similar layout
Assigner board removed from the build
In the meantime I’m building a JX-10 rack mount version with the spare boards, here is the finished front panel.
Just got to make a front panel template and cut the panel out, but other than that it’s all installed and working. I had a couple of faults, voice board C was broken because I missed a pin when soldering in the Vecoven V4 upgrade and the volume control didn’t work as I inverted the signal after the VCA and that normally isn’t an issue, but when you are using the VCA to control a voltage you need to invert it back again. So I added an extra TL072 and inverted the stereo pair back to a positive voltage.
Another addition to the build.
