Distorted output from an Akai S950 sampler


Mmmm, chips. Barely 20 minutes into using my newly-purchased S950, the sound became extremely, digitally-ish distorted. So before I start crying, it’s a good chance to whip the top off the thing and see what we’ve got in the grey box. Mmm, circuit board porn.


…and it’s a lot busier in here than I expected; the weight of the box (almost 11kg according to the manual) should have been a clue here. But then this thing did come out in 1988 – my (also broken…) E-MU ESI 2000 is virtually empty by comparison.

So you can see the power supply on the left, with a large heatsink. There’s at least two big main circuit boards, the lower one hidden by top one, which I’m guessing is the voice board, because of the eight identical columns of chips, one for each voice. I imagine the main out is on the right-hand side somewhere. Underneath this I imagine we have some sort of CPU board. There’s a large trapdoor underneath for adding two 750KB expansion cards. If your S950 says 512 Kwords on bootup, it’s unexpanded – 1024 Kwords 1536 Kwords means it’s fully expanded to 2.25MB.

I was hoping that there was some sort of loose connection rather than a blown opamp or power supply problem, which I’d be rubbish at fixing and tricky to track down. There are wires connecting the circuitboard to the audio out board – waggling and pushing the wires down into the socket the wires in this area (top-right as you look at the picture above) fixed the problem.


So I’ve not had a great chance to play around with it, but here’s a not-particularly indicative scratchy loop of a TR-606 and Boss handclap, with heavy spring reverb, sampled at 5KHz, sat next to an MS20 bassline recorded straight into Ableton Live.

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  1. 11th October 2021Martial Foucault says:

    Hi, I like your blog and your posts, I have one question, have you find the schematic on an EXM006 memory expansion for the S950. I would like to build 2 extensions. Have you any ideas where I could find some ressource to do that ?
    Thanks a lot

  2. 12th October 2021ua726 says:

    Hello! I’ve never thought to try to and make a S950 memory expansion. Mine has more or less a floppy disks’ worth of memory in it – any more and I’d be having to save the memory over a couple of disks, which sounds like even more hassle than it already is.

    There’s someone selling S950 cards on eBay right now for about £50. I imagine it’d be cheaper to make your own, but not by much, and perhaps only if you get it right first time.

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