A firmware update for the AKAI AX60 Synthesizer
For several years I have been interested in learning more about the AKAI AX60, to see if it might be possible to add a few features to the firmware. I recently found one for what seemed like a reasonable price so I grabbed it. Unfortunately, the front panel has rust under the paint in a number of places, so it will always look rough. The electronics were repairable however, so I now have a unit for firmware development. I visited a few web forums where the AX60 was being discussed, and lined up some people to help me test the new firmware, and also suggest improvements.
The first thing to look into was what several people described as "jumpy sliders". As it turns out, the AX60 slider code is a little unusual. Slider values are converted into 8-bit binary values, so the range is 0-255. When a slider is found to be in motion, the value only needs to change at least 2 counts for the patch value and CV to be updated. But once the slider stops moving for about 1 second or more, in order for the patch value and CV to change, it has to move at least 5 counts in-between two successive reads of the slider. So it has to be moving fairly fast for the patch value and CV to be updated. Once the threshold is exceeded, the slider is considered to be "moving" and the threshold drops to 2 counts instead of 5. My guess is that the code was set up this way to avoid the "patch change" decimal point coming on from dirt in the sliders or maybe circuit noise. Anyway, I felt that it was better to change the code so that the threshold would always be 2 counts instead of 5.
My new firmware (which used the V1.2 code as a starting point) has been tested by six AX60 owners, and is now available. Here are the new features:
1) MIDI Sysex patch save and restore - saves or restores all patches in one operation (tape save/load works as before)
2) MIDI cc parameter changes are now supported
3) Non-volatile storage of MIDI channel setting and current patch
4) Slider code modified as described above to avoid jumpiness
5) Adjustable Unison de-tune feature. (Not active in split mode) (can be disabled)
6) Random arpeggiator mode instead of "play all notes" mode (can be disabled)
7) Arpeggiator up/down mode which doesn't repeat the top and bottom keys (can be disabled)
8) Slow LFO mode which halves the frequency over the entire range of the LFO (can be disabled)
9) VCF resonance slider taper mod to move oscillation point up (overall range is not changed) (can be disabled)
10) ADSR slider tapers mod to increase effect in the lower part (overall range is not changed) (can be disabled)
11) MIDI clocking of arpeggiator with choice of 48,24,12, or 6 PPQ (can be disabled for internal or 1/4" jack clocking)
12) Sustain mode can be activated using Arp Hold switch
13) MIDI Note velocity added to VCA EG Depth setting mode (but new setting also affects notes played on AX60, can be disabled)
The original AX60 firmware EPROM was pretty much full, so no room for the new code. To allow using a larger EPROM, it was necessary to change the decoding of the CPU address space a little. To accomplish this, I designed a small daughterboard that plugs into two IC sockets on the AX60 digital board. Here is how it looks (The EPROM window would normally be covered, of course):
To install the pcb, the AX60 digital board must be removed from the synth. A 16-pin IC is then removed from the board and replaced by an IC socket. The EPROM pcb plugs into that socket and the socket for the original EPROM. Assembling the EPROM pcb and installing it in the AX60 takes 1-2 hours. Here are the instructions for installing the EPROM pcb. No traces are cut and no jumpers are added to the AX60 pcb.
As noted above, MIDI CC's are now supported for controlling patch parameters. Here is a document containing the CC assignments, along with some additional information about using the new firmware.
Many of the new features can be disabled if desired, restoring the original behavior. To accomplish this, a number of pairs of switches are re-defined in "MIDI channel setting" mode to turn particular features on or off. In this mode, pressing these switches does not perform their normal function. It only turns one of the new features on or off. The settings selected in this mode are saved when the synth is powered off. Here is a diagram that shows which switches are used and what they control.
I am offering a blank pc board plus the parts needed to assemble it for $75 plus postage. Please contact me if you are interested. I will not be offering assembled boards.
If you have an original factory cassette for the AX60, and would be willing to have me convert it to sysex for others to use, please let me know.
Please note: Taking an AX60 apart and installing the new pcb must be done carefully, or damage to the synthesizer could result. It should only be attempted by someone familiar with this type of work. I will not be responsible for any damage to any instrument caused by either proper or improper use of the code offered here.
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