Roland Super JX-10

Analog monster width 12 voice polyphony, 24 oscillators

Difference to JX-8P and some images from two repair jobs

Some people seams to dispute Roland’s marketing buff telling us Super JX (MKS-70/JX-10) are two JX-8P in one instrument. Reason are they prefer the sound from JX-8 over Super JX which imply there are differences on the hardware. And after reading Eric Persing ‘s comment on the self-oscillating filter in Super JX I got curries to find out the difference in circuit.

Initial findings show differences around the filter chips. Several changes around control functions but as these also are under software control the most interesting parts to look at seems to be the load and filter frequency caps on pin 6 (Load), pin 10 (C4), pin 11 (C3), pin 12 (C2), pin 13 (C1). Cap value for C1, C2 and C4 are identical on all units, leaving pins for C3 and Load to investigate.

Interestingly we find that the MKS-80 from rev5 also use the same IR3R05 Filter/VCA chips and none of the subjects use identical values as it turns out.

Super JX also differ from the JX-8 by it's exponential control of pin 5 (Level) on IR3R05. This signal is generatet from summed audio of all 6 voices after the HPF and are mixed with CV controll though a 47k resistor (R66).

Filter difference between JX-8P and JX-10

Update 5-2019 — From mail conversation with Fred Vecoven currently migrating his JX-10 v3 firmware for use on in the JX-8P I learned the original code for filter control are identical for both JX8 and JX-10. Implying JX-8P will not get self oscillating filters from new firmware alone.

Filter values
C3 pin 11 Load pin 6
JX-10 220pF 1K5/10uF
JX-8P 10nF 3K3/10uF
MKS-80 rev5 10nF 3K3/47uF
The JX synthesizers employ a four-pole lowpass filter, which rolls high frequencies off at a rate of 24dB per octave. There is a slight difference between the maximum resonance amount setting in the JX-8P and the JX-10. When pushed to its upper limit, the filter in the JX-10 will oscillate producing a sine wave, but this effect is not possible on the JX-8P. Eric Persing, Keyboard Magazine Oct 1986
JX-10

Further dive into the schematics we learn that after the audio signal leaves the VCF all 6 voices on each module board are summed through an op-amp and then passed to the select-able HPF where filter values for all three position are identical for both JX-8 and JX-10.

Signal are then split for chorus bypass and entering the chorus circuit where both JX-8/10 make use of the MN3009 / MN3101 combination. With minor difference to the oscillation control circuit for BBD driver MN3101 main difference seems to be use of op-amps (M5218P) in JX-10 for low pass filters before and after the MN3009 BBD, — as opposed to discrete transistor circuits in JX-8P.
Limiter before the LPF in front of the chorus found in JX-8 are not duplicated to the JX-10, — use of exponential control of the IR3R05 level might have made it obsolete?

From the chorus circuit audio signal now enter the master volume VCA. For JX-10 this is a integrated logarithmic VCA M5241L whereas the JX-8 use a dual transistor 2SA798G with an op-amp (probably M5218). For JX-8 output are taken direly from this op-amp while the JX-10 has a dedicated output driver (M5218L) after the VCA chip.

On a side note the Mono Total Mix output on JX-10 are summed after the headphone amplifier with option to pad down the mono signal with a three positions switch. For JX-8 this switch will pad down the stereo output.

Block diagram

jx10/Super_JX-10_016.jpg
To view high resolution images, right click on image and select View image or Save image

Select file from list below

ProgrammingSuperJX.pdf
13.0M Compressed file
Roland M-64C_01.png
318.5K
Roland M-64C_02.png
622.2K
VCF Difference JX-8 vs MKS-70.png
125.3K
jx810block.png
347.1K
voice board JX8.png
95.3K
voice board MKS70.png
106.4K
Roland_M-64C (1).JPG
1.4M
Roland_M-64C (2).JPG
1.5M
Roland_M-64C (3).JPG
878.1K
Roland_M-64C (4).JPG
797.0K
Roland_M-64C (5).JPG
1.7M
SuperJX10.JPG
471.0K
Super_JX-10_001.jpg
226.1K
Super_JX-10_002.jpg
119.2K
Super_JX-10_003.jpg
247.8K
Super_JX-10_004.jpg
131.9K
Super_JX-10_005.jpg
212.6K
Super_JX-10_006.jpg
170.2K
Super_JX-10_007.jpg
165.5K
Super_JX-10_008.jpg
90.9K
Super_JX-10_009.jpg
224.7K
Super_JX-10_010.jpg
229.4K
Super_JX-10_011.jpg
187.7K
Super_JX-10_012.jpg
265.8K
Super_JX-10_013.jpg
258.2K
Super_JX-10_014.jpg
285.9K
Super_JX-10_015.jpg
190.9K
Super_JX-10_016.jpg
193.0K
Super_JX-10_017.jpg
179.2K
Super_JX-10_018.jpg
314.8K
Super_JX-10_019.jpg
276.1K
Super_JX-10_020.jpg
217.6K
Super_JX-10_021.jpg
160.0K
Super_JX-10_022.jpg
202.8K
Super_JX-10_023.jpg
179.8K
Super_JX-10_024.jpg
175.6K
Super_JX-10_025.jpg
238.8K
Super_JX-10_026.jpg
272.7K
Super_JX-10_027.jpg
274.5K
Super_JX-10_028.jpg
201.3K
Super_JX-10_029.jpg
267.3K
Super_JX-10_030.jpg
317.4K
Super_JX-10_031.jpg
374.7K
Super_JX-10_032.jpg
317.0K
Super_JX-10_033.jpg
271.0K
Super_JX-10_034.jpg
315.8K
Super_JX-10_035.jpg
384.8K
Super_JX-10_036.jpg
283.8K
Super_JX-10_037.jpg
439.6K
Super_JX-10_038.jpg
394.3K
Super_JX-10_039.jpg
230.2K
Super_JX-10_040.jpg
209.4K
Super_JX-10_041.jpg
296.4K
Super_JX-10_042.jpg
298.3K
Super_JX-10_043.jpg
365.9K
Super_JX-10_044.jpg
409.0K
Super_JX-10_045.jpg
218.1K
Super_JX-10_046.jpg
153.1K
Super_JX-10_047.jpg
173.0K
Super_JX-10_048.jpg
310.8K
Super_JX-10_049.jpg
217.6K
Super_JX-10_050.jpg
158.3K
Super_JX-10_051.jpg
146.5K
Super_JX-10_052.jpg
258.1K
Super_JX-10_053.jpg
191.7K
Super_JX-10_054.jpg
310.8K
Super_JX-10_055.jpg
275.6K
Super_JX-10_056.jpg
204.5K
Super_JX-10_057.jpg
279.9K
Super_JX-10_058.jpg
167.2K
Super_JX-10_059.jpg
141.5K
Super_JX-10_060.jpg
206.1K
Super_JX-10_061.jpg
365.4K
Super_JX-10_062.jpg
379.6K
Super_JX-10_063.jpg
249.3K
Super_JX-10_064.jpg
370.3K
Super_JX-10_065.jpg
259.7K
Super_JX-10_066.jpg
207.0K
Super_JX-10_067.jpg
197.4K
Super_JX-10_068.jpg
182.7K
Super_JX-10_069.jpg
236.8K
Super_JX-10_070.jpg
285.2K
Super_JX-10_071.jpg
246.7K
Super_JX-10_072.jpg
382.5K
Super_JX-10_073.jpg
265.4K
Super_JX-10_074.jpg
248.3K
Super_JX-10_075.jpg
202.7K
Super_JX-10_076.jpg
278.8K
Super_JX-10_077.jpg
258.7K
Super_JX-10_078.jpg
197.5K
Super_JX-10_079.jpg
217.1K
Super_JX-10_080.jpg
236.8K
Super_JX-10_081.jpg
405.3K
Super_JX-10_082.jpg
431.5K
Super_JX-10_083.jpg
238.5K
Super_JX-10_084.jpg
227.5K
Super_JX-10_085.jpg
206.8K
Super_JX-10_086.jpg
219.0K
Super_JX-10_087.jpg
214.2K
Super_JX-10_088.jpg
205.1K
Super_JX-10_089.jpg
178.5K
Super_JX-10_090.jpg
279.5K
Super_JX-10_091.jpg
255.2K
Super_JX-10_092.jpg
246.2K
Super_JX-10_093.jpg
231.8K
Super_JX-10_094.jpg
223.8K
Super_JX-10_095.jpg
245.2K
Super_JX-10_096.jpg
204.1K
Super_JX-10_097.jpg
219.7K
Super_JX-10_098.jpg
202.4K
Super_JX-10_099.jpg
290.5K
Super_JX-10_100.jpg
331.3K
Super_JX-10_101.jpg
319.3K
Super_JX-10_102.jpg
196.5K
Super_JX-10_103.jpg
189.7K
Super_JX-10_104.jpg
325.1K
Super_JX-10_105.jpg
387.2K
Super_JX-10_106.jpg
250.5K
Super_JX-10_107.jpg
239.6K
Super_JX-10_108.jpg
159.3K
Super_JX-10_109.jpg
152.1K
Super_JX-10_110.jpg
161.9K
Super_JX-10_111.jpg
140.8K
Super_JX-10_112.jpg
219.6K
Super_JX-10_113.jpg
114.9K
superjx.jpg
648.8K

DCO explained: https://www.youtube.com/watch?v=mqY6cVJS9fo

First MIDI upgrade for JX-10 with technical information: http://www.colinfraser.com/jx10/jx.htm

Firmware 3.xx/4.xx: http://www.vecoven.com/superjx/superjx.html


Comments

Your comment are welcome

Name:


Email: optional, will be hidden


Comment:    



Please do not make support question private as it brake with what this site is trying to do which is to share information to many with multiple contributors
All spam is reported adding to your international IP blocking quota.