For a while, Akai was making both samplers (s612, s900, s950) and analog synths (ax60, ax80, ax73, vx90) and they had this proprietary system for connecting them — a 13-pin cable that lets you run multiple channels of output out of the sampler and into the synth, allowing the sampler’s voices to be polyphonically processed by the synth’s analog filters and so on. This sounds like a great setup, so I was surprised when I recently scored an s950, vx90, and 13-pin cable to find very little info on this online, aside from the s612/ax60 combo. After a bunch of experimenting with my setup, I decided to record what I found for posterity.

• The 13-pin cable is just a multi-channel audio connection
• Each sampler voice corresponds to a single channel in the cable
• The s612 has 6 voices, and the s900 and s950 have 8 (not sure about s700/x7000)
• In the s950, a simple program with one keygroup assigned to “all outs” will get sent out the cable, apparently rotating through the 8 channels. Assigning the keygroup to a specific out will seemingly always send the audio out the corresponding cable channel.
• In the s950, the individual channels are indeed monophonic (i.e. the do correspond exactly to the 8 voices). A later event will seemingly always cut off an earlier one.
• The vx90 has six voices and apparently only listens to the first 6 of the 8 cable channels. So if it’s hooked up to an 8-voice sampler like the s950 that’s rotating through its voices, every 7th and 8th note will be dropped by the vx90
• The s950 seems to have no way to assign a keygroup to a set of outs (i.e. outs 1-6). You can assign to a single out or to all (or to left/right, even/odd, but that doesn’t help).
• If 2 keygroups are assigned to outs 7 and 8 while a third is assigned to all outs, the s950 is not smart enough to prevent the all group from sometimes using voices 7 and 8 and therefore cutting off those notes. So you seemingly can’t trick it into just using 1-6.
• Since individual keygroups can be assigned to specific outs, a multi-keygroup program (e.g. a drumkit) could be set up to only use outs 1-6.
• However, even if you get the s950 to not use outs 7 and 8, there seems to be no way to ensure that, on receiving a midi note, the s950 and vx90 will choose the SAME voice channel to use. So the notes still won’t line up.
• The s612 and ax60 combo apparently address this by having a midi mode where the voices are controlled on 6 separate midi channels so that the two units can be forced to allocate the same voices. Presumably if you can put the ax60 in this mode, you could do something similar with the s950 by assigning keygroups to multiple midi channels. I don’t have an ax60 and don’t know if this is true.
• If the vx90 is in unison mode (i.e. all 6 voices stacked), it will pick up audio on any of the 6 cable channels, so that works. Of course, this is just using the vx90 as a single monophonic filter on the s950’s output, which could be accomplished with any external filter.
• You could also presumably make a cable that would wire a single audio channel to all 6 voice inputs in the 13-pin cable, allowing the vx90 to be used as a monophonic filter when in poly or dual mode, for whatever that’s worth.
• The upshot is that, as far as I can tell, the whole Akai-sampler-synth connection thing is mostly bogus and unusable, unless you have an ax60, or just want to use the vx90 unison mode.
• I believe everything I say about the vx90 applies to the ax73. I don’t know about other synths that may have the 13-pin connection.