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  #1  
Old 10-17-2013, 12:22 PM
Mondovermona Mondovermona is offline
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Default UMR2 - Kawai SX 210 MIDI retrofit

The Kawai SX210 (Teisco) IMHO is an underrated and very interresting 8-voice synth from 1982/1983 with computer controlled analog LP filters (SSM2044), a separate HP filter, and a three phase BBD based ensemble effect in stereo, which (except for the stereo) closely resembles the funcion of BBD ensemble effects built in early string machines (Eminent 310U, ARP Solina, Logan String Melody and others).

It not only produces fresh and interesting sounds, bus also has nice looks. There are several good reasons to include MIDI to this instrument to get it back on the track.

Here's the keyboard matrix - any thoughts?
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File Type: pdf Kawai SX-210 Keyboardmatrix.pdf (86.5 KB, 381 views)
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Old 10-17-2013, 12:34 PM
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Originally Posted by Mondovermona View Post
The Kawai SX210 (Teisco) IMHO is an underrated and very interresting 8-voice synth from 1982/1983 with computer controlled analog LP filters (SSM2044), a separate HP filter, and a three phase BBD based ensemble effect in stereo, which (except for the stereo) closely resembles the funcion of BBD ensemble effects built in early string machines (Eminent 310U, ARP Solina, Logan String Melody and others).

It not only produces fresh and interesting sounds, bus also has nice looks. There are several good reasons to include MIDI to this instrument to get it back on the track.

Here's the keyboard matrix - any thoughts?
Hi Mondovermona,

As you probably determined already, it looks like active-low matrix polarity with select on KS0-KS7 and data on B0-B7.

It should be straighforward, but the usual caveat applies: to be certain, it's always a good idea to double-check the signal voltage with a scope.
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Old 10-17-2013, 01:00 PM
Mondovermona Mondovermona is offline
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Sorry, I forgot to include the CPU circuit. The scan signal is produced out of a LS138 at 5V supply and the data lines are clamped to +5V (see lower right end of the schematic). I expect the voltages in the keyboardmatrix to be in the proper range for the UMR2.
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File Type: pdf Kawai SX-210 CPU board.pdf (223.7 KB, 285 views)

Last edited by Mondovermona; 10-17-2013 at 01:10 PM.
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Old 10-21-2013, 07:43 PM
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Originally Posted by Mondovermona View Post
Sorry, I forgot to include the CPU circuit. The scan signal is produced out of a LS138 at 5V supply and the data lines are clamped to +5V (see lower right end of the schematic). I expect the voltages in the keyboardmatrix to be in the proper range for the UMR2.
Aha, yes. It looks good to me. Please let us know how it works out!
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Old 12-19-2013, 09:33 PM
Mondovermona Mondovermona is offline
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Hi John,

I have now installed the UMR2 kit with the SX210. Pictures will follow soon.
Data I/O lines of the UMR2 are connected to B0-B7 of the SX210's keyboard, Select lines are connected to its KS0-KS7. Polarity is set to (-) (active low). The UMR2 is powered directly via the 5 Volt supply for SX's CPU (digital +5V)

In the setup procedure of the UMR2, a incoming MIDI signal to set low Key no. and MIDI channel is received, but in setup step two the UMR2 does not respond to any keystrike on the connected SX's keyboard. Accordingly, I cannot complete the initial setup procedure.

Keyboard control of the SX through its own keyboard is preserved and fully functional even with the powered, yet not set up UMR2 in place.

I measured signals at the Data I/O and found constant 5 Volts (due to the pull-ups on the SX's CPU board (see above) as expected. The Select lines also show high level with intermittent low going pulses. I found that by pressing a key on the keyboard the respective Data line goes intermittendly low, but only from 5 Volt to about 1.8 Volts, not to zero. Might this be the reason why UMR2 does not sense the keystrikes? Or is it an "unusual" scanning procedure at the select lines.

What test shall I perform next? Which measures are to be taken to get the UMR2 running?
Your help is greatly appreciated.
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Old 01-09-2014, 08:39 PM
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Hi Mondovermona,

Quote:
Originally Posted by Mondovermona View Post
Hi John,

I have now installed the UMR2 kit with the SX210. Pictures will follow soon.
Data I/O lines of the UMR2 are connected to B0-B7 of the SX210's keyboard, Select lines are connected to its KS0-KS7. Polarity is set to (-) (active low). The UMR2 is powered directly via the 5 Volt supply for SX's CPU (digital +5V)

In the setup procedure of the UMR2, a incoming MIDI signal to set low Key no. and MIDI channel is received, but in setup step two the UMR2 does not respond to any keystrike on the connected SX's keyboard. Accordingly, I cannot complete the initial setup procedure.
Ok. Just to confirm: when you send the initial "low note" to the UMR2, does the UMR2's red LED flash, and then does the UMR2's green LED begin blinking continuously?

Quote:
Keyboard control of the SX through its own keyboard is preserved and fully functional even with the powered, yet not set up UMR2 in place.

I measured signals at the Data I/O and found constant 5 Volts (due to the pull-ups on the SX's CPU board (see above) as expected. The Select lines also show high level with intermittent low going pulses. I found that by pressing a key on the keyboard the respective Data line goes intermittendly low, but only from 5 Volt to about 1.8 Volts, not to zero. Might this be the reason why UMR2 does not sense the keystrikes? Or is it an "unusual" scanning procedure at the select lines.
Ok. Did you measure the voltage using a scope or with a multimeter?

If you are using a multimeter, the meter will "average" the voltage over time, so that a signal oscillating between 0V and 5V will read as a DC voltage somewhere in between.

If you are using a scope and noted that the low-level voltage is 1.8V, then yes, this could be the source of the problem.

Please let me know more about your measuring method and we will continue from there.
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Old 01-14-2014, 10:41 AM
Mondovermona Mondovermona is offline
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Thank you for you answers, John.

Yes, I have a scope. so the number I gave were taken from its screen.

I am afraid that your UMR2 is not capable of dealing with the way the SX210 scans the keyboard.

As you may know, I have successfully retrofitted my OB-Xa with the UMR2. Now I failed in the same with the SX210 which has basically the same keyboard and straight forward scan circuitry (as confirmed by you in this thread). However, after having compared the scan signals of both synths with the scope, I feel that there is a substantial difference in the nature of the signals: While the Oberheim scans pretty slowly with periodical patterns on each of the scan channels in the range of some milliseconds, the scan signals of the Kawai look pretty different: there seem to be some kind of bit pattern or the like on each of the 8 scan lines. The low active signal is in the range of less than a microsecond (my old oscilloscope of 35 MHz bandwith cannot fully resolve or trigger on these very short pulses). There seems to be a completely different time regimen or scaning procedure. Note that the Kawai's CPU is running at 12MHz (which I consider pretty high for a CPU in a synth of 1981/1982). Please enlighten me. BTW, at what speed is the UMR2 running?

Contrary to what is fond in the schematic drawing (see previous thread) the "scan out" lines are clamped to +5V, as well as the "scan/data in" lines).

Your continued assistance is highly appreciated!!
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Old 01-17-2014, 11:43 AM
JE:5 JE:5 is offline
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Hi, I am new here and found this thread by searching google for info on MIDI retrofitting a Kawai SX-210 that I have just picked up.

I have read this thread and understand that the MIDI in works but the MIDI out does not and that the set up procedure relies on the MIDI out working in order to complete?

I am not actually in need of a MIDI out and only require basic MIDI in (Note on, note off). So, is there a way of spoofing the UMR2 into completing the setup procedure and just having the MIDI in working? Or have I totally misunderstood this thread!

Cheers.
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Old 01-22-2014, 01:44 PM
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Quote:
Originally Posted by JE:5 View Post
Hi, I am new here and found this thread by searching google for info on MIDI retrofitting a Kawai SX-210 that I have just picked up.

I have read this thread and understand that the MIDI in works but the MIDI out does not and that the set up procedure relies on the MIDI out working in order to complete?

I am not actually in need of a MIDI out and only require basic MIDI in (Note on, note off). So, is there a way of spoofing the UMR2 into completing the setup procedure and just having the MIDI in working? Or have I totally misunderstood this thread!

Cheers.
HI JE:5, welcome to the forum.

It looks like Mondovermona can't get either MIDI in or MIDI out to work with the SX-210. In general, however, when the UMR2 is compatible with the host keyboard, the setup can always be completed. It is no problem to use the keyboard only as a sound module.

Mondovermona, I'm not sure that I have any additional insight for you about this particular keyboard model. The UMR2 runs at an effective instruction clock of 8MHz, however, this is not necessarily indicative of it being "too slow" when compared to the clock speed of the host microprocessor. The keyboard scan rate is typically much slower than the instruction clock.

Thank you for posting your findings! Please let me know if I can provide any other information.
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