The Vecoven Digital PWM enhancement for the Roland Super JX involves adding a digital daughter card to each voice board. Extensive de-soldering of four counter chips, a capacitor and processor is required for each tone board.
It has been derived from the JX8P PWM modification and results in a super neat install, it is my favourite SuperJX modification, better still, in the JX10, the keyboard assembly does not have to be removed! If you have good de-soldering skills, it is a straightforward modification to perform.
Details for the PWM upgrade are here: Vecoven Super JX
What Can It Do?
Pads: Check out this demo by Serge Pomorski on SoundCloud: Mother of All Pads
Bernd Bruening has developed a set of PWM patches and plays them on YouTube.
How It Works
On each voice board, the 4 counter chips are replaced by a digital daughter board that simply substitutes the Square wave output from the digital circuitry with one that is capable of PWM. New firmware utilises the new features of the replacement counters that are implemented inside an FPGA.
Fred has done an amazing job of replacing all functionality of the original counter chips, along with the bugs and nuances the chips have to replicate the old functionality of the DCOs very precisely. So much so that it works with Roland firmware too. Additional registers have been added to allow custom firmware to exploit PWM features.
New circuitry is very low power and as the counters were some of the largest heat generators in the instrument, the reduction in power consumption is astonishing with a 300 mA saving per voice board – that’s insane!!!
A new high speed 8032 processor derivative is also used to execute code up to 3 times faster. Not only can more code be executed but also has an additional benefit for fast and precise envelope generation. The improvement in speed, allows much faster attack envelopes unlike the original Roland design.
There are so many additional options including additional envelopes and LFOs that can be used to manipulate the PWM feature. In experienced hands, the change can be dramatic.
The number of extra parameters are vast, they are described on Fred’s site.
Testing the Analogue or Digital versions side by side, yields same results from an audible perspective, choice is simply how you wish to modify the instrument; wiring or de-soldering. The Analogue version is lower cost too as it is a much simpler PCB that you can build yourself. An important point to remember is that the SuperJX uses DCO…..but….. with analogue wave-shaping, therefore small and pleasant imperfections are inevitable with either version.
I Got It! Where Do I Start?
To begin the journey, edit a tone and set oscillator type to “PULS”, a PWM value and off you go.
An excellent video showing what to edit to get going yet hear how brutally different the modification can be has been made by Joakim Floke on YouTube.
All of the manuals for the Vecoven upgrades are located on his site in the downloads section, many revolve around the JX 10 but equally applicable to the MKS 70 as only the front panel controls differ.
Installation JX10 & MKS70
The example below is for the JX10 but the MKS70 is the same for each voice board. In total, on the JX10 it took about 3 to 4 hours. Only the voice boards have to be removed, so little has to be disassembled.
It is strongly recommended to use an electric de-soldering tool for this task. When doing so, frequent cleaning of the tool is necessary due to the low quantity of solder sucked out in each operation as it causes blockages more readily on low cost tools.
For hints and tips on de-soldering ICs from the voice board, see the Vecoven Analogue PWM fitting guide where it details processor removal and checking of plated through hole connections. When removing ICs, it is very easy to accidentally remove the plating on the inside of the hole and cause all manner of strange faults on the processor bus.
This modification requires a medium level of practical electronics skills.
In these pictures you may notice the blue mat and occasional view of a wrist band. This is to keep static electricity under control.
They can be purchased from eBay for very little money. Many electronic parts in the SuperJX are no longer available, taking anti-static precautions reduces the possibility of damage or weakening of old semiconductors.
IC & Capacitor Removal
Remove IC10, 19, 20, 21, 22 and C119. Caution required around C119 because the legs are folded flat before soldering and care needs to be taken to avoid damage to the PCB.
Once done the PCB should look like this.
The components removed, look like this.
Fit the new ROM, CPU and place the digital counter card in position. The CPU can be socketed and a high quality socket is provided with the kit. If wanted, it is possible to roll back to Roland firmware if putting the old CPU back in, or any 8032 derivative.
Solder the digital counter card in place making sure that no bridges or shorts are made.
Fit the capacitor to the underside of the PCB. It is a good idea to use a small piece of electrical tape but likely not necessary if the insulation on the capacitor body is thick enough. However it does protect the PCB traces against effects of vibration if instrument is transported.
Repeat all of the above for the other voice board.
Finally everything can be reinstalled into the instrument.
Copyright © 2021 Super Synth Projects, Guy Wilkinson
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