Following up on my last post about connecting Akai samplers and synths with their proprietary 13-pin cable, I managed to get it working polyphonically with my s950 and VX-90. I expect this would also work with the AX-73 (which is virtually identical to the VX-90) and the AX-60 (which is similar) synths, and with the s900 and s612. Based on what worked for me and stuff I’ve read about people using the s612/AX-60 combo, I suspect all the units with the 13-pin connection work (somewhat) similarly.

How to get s950 voices to be processed polyphonically by the VX-90:

1. Connect the voice out of the s950 to the sampler in of the VX-90. I found one on eBay described as “for Roland cable GKC-3 13-pin” — it’s a knockoff of a Roland guitar synth cable. If you get some other cable, make sure pins 1-7 are connected (1-9 to get all 8 voices).
2. Connect the MIDI out of the VX-90 to the MIDI in of the s950. Not the thru! The VX-90 is going to transform the midi notes you send it before passing them on to the s950. If you want to be able to run the s950 without the VX-90, you’ll need to be able to reroute its MIDI input.
3. Connect the outputs of the VX-90 to your mixer or amp.
4. Set the VX-90 MIDI channel to 1 (edit, parameter 70). Set the s950 MIDI channel to 1. You can probably use other channels, but the two are actually going to communicate over multiple channels, so it’s easiest to just set them at 1 and let them do their thing.
5. Create a patch on the VX-90 with sample input (parameter 06) set to ON and A/B balance (param 07) set to 100 (or at least 50). Set assignment mode (param 50) to POLY and portamento (param 51) to 0. For starters, open the filter up all the way (cutoff, param 10, to 100, and resonance, param 11, to 0).
6. Create a program on the s950 with a single keygroup containing a simple synth sample, with the filter wide open (to 99). Duplicate this keygroup until you have 6 identical keygroups. Set the midi channel of KG1 to 1 and its output channel to mono 1. Set KG2 to channel 2 and mono 2, and so on.
7. Select your sample patch on the VX-90 (the midi mode that communicates with the s950 is only enabled when you select a patch with sampler input set to ON).
8. Send the VX-90 some midi notes. You should hear the s950 sample playing through the VX-90. Make sure when you run through a series of notes, all the notes are audible and that when you play a chord, you hear all the notes simultaneously. Play with the filter (param 10) to see it processing the sampler output. Assign some envelope modulation to the filter cutoff (param 13) to hear independent filter processing for each voice.
9. To tweak your program on the sampler, edit the keygroups with KG set to “all”, which will change all 6 keygroups at once. Of course, you could give them different settings if you want a sort of random note effect.
10. Play with the A/B balance (param 07) to mix the sampler with the internal oscillator. By turning the tune knob on the front of the VX-90 you can get a nice detune going between the two. You should also be able to put the VX-90 in DUAL or UNISON mode (param 50) to get extra stacking. If you just want to use UNISON, you actually don’t need all the keygroup hoo-ha on the sampler; that’s just necessary for polyphonic operation.

Why does this work? When the VX-90 is in sampler mode (i.e. when the current patch has sample input enabled, param 06) it spreads its midi notes across 6 channels, one corresponding to each voice. If you send it a series of notes on channel 1 and monitor the output (the  s950 has a midi monitor function), you’ll see the notes come through on channels 1-6. The s950 program is set up to receive on those 6 channels and route that note through the corresponding output in the 13-pin cable. The VX-90 and s950 have to be in sync this way to make sure the sound from the sampler goes through the corresponding voice that is being played at the same time.