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MOD: Yamaha CS-01

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  • MOD: Yamaha CS-01

    I have wanted a CS-01 for many years.. They were just too expensive and too hard to come by for me to bother. Then recently i got a nice one on eBay from the UK for a reasonable but still overpriced price.. It's a black one, with a switch for the resonance.. think it's a Mk.1.

    If You ever wanted the sound of the Casio divide-down home organs, but with a synth control surface, the cs-01 is for You!

    Read this: http://rga24.blogspot.ie/2010/06/yamaha-cs01.html and look at this: http://home.earthlink.net/~kerrybradley/id11.html for a starting point or 2. I really wanted to get the Resonance adjustable, and although i have a breath controller, i have no interest in it, nor in using the jack to inject voltages into the CS01. the problem with the CS01, and most Yamaha and Korg 80's/70's gear is it's horrible negative voltages and such arse that i really could not be bothered with tapping. So, no CV or GATE input mods here, and although the Highly Liquid kit for the cs-01 here: http://highlyliquid.com/hl2012/blog/category/cs01-midi is nice, it can wait for another episode.

    So, to do the Resonance mod, i used the VCA knob for the breath controller - it's 10k, the same value as the resistor i would be replacing with it. To do this, you must unsolder the knob from the board, then bend the 3 pins back and up away, so they don't use the holes they used to any more, then re attach the knob by the 2 support lugs either side. then run wires from the holes you have after removing the 10k resistor in the resonance switch circuit to the middle and either of the outer legs on the pot. now you can adjust the 'Q' trimmer on the board near the filter section until it screams with the new knob fully open. experiment with this trimmer, and the VCF cutoff trimmer so you can have a totally closed filter when the filter is closed (duh!) then you can get the best scream from the resonance as you approach a closed filter with lots of res dialled in.

    The previous res switch can be re-used to switch in & out the other mod i did. Isolate the switch by cutting the traces as in the picture. You don't need to worry about this effecting the filter, it does not. Resonance is now set up to depend on where the VCA BREATH CONTROL pot is... So, Then run a wire from the OSC out of the main chip (pin 15) thru' a 10uf cap to one side of the switch, then from the other side of the switch run wire to a the VCF knob for the BREATH CONTROL - do the same trick as with the VCA knob before this - ie: remove the pot, but this time when re-soldering it, leave the centre leg back in it's hole - lift the other 2 and use either to attach the wire from the VCO chip pin 15 via the switch and cap. See? what we are doing is using the route from the middle leg of the VCF BREATH CONTROL pot to the Filter cutoff - and we are feeding it with the VCO out, but via the old (now useless) switch for RES. The reson for this is so we can enable/disable it easily, and not have to mount another switch anywhere.

    This makes for some crazy-assed modulation of the filter with the OSC, especially when it is is screaming!

    Finally, i decided to do the bending/waveform trick. I mounted a toggle switch on the bottom case near the mod wheel (see pics) and ran 3 wires to the waveform switch as shown (the gray wires) and managed to be able to make 2 new waves.. a totally batshit one, no geometric shape, just mutation, and a hybrid slope saw, switchable of coarse. these work best when the saw/sin wave is selected, but they do have an effect on more then waveshape - some combinations cause the keyboard scanning to trip up and duplicate notes, and some cause the D notes to be 1 note high across the keyboard! no worries, nobody cares!
    Last edited by playthatbeat; Sat 31-05-2014, 4:58 PM.
    jUst plAythAtbEAt

  • #2
    This is how it sounds.

    I open with just the stock machine, doing a casio bassline lol.. then i start cranking in the new res mod - remember i re-set the levels of the 'Q' (feedback really) and the 'Fc' (range of the filter cutoff) to allow the filter to sweep from almost total silence to fully open with no ENV to FILTER enabled. If you do not adjust these 2 pots, then all you get from the new Res control is a graduated version of the crap that was there on the switch! You need to crank up that feedback on the board to get it screaming.. Then i start to add in the OSC to FILTER mod, and i tweak the 2 new controls a bit. i then do all of the above while changing waveforms on the selector and also with my bend.
    Attached Files
    Last edited by playthatbeat; Sat 31-05-2014, 4:48 PM.
    jUst plAythAtbEAt

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    • #4
      Last pic - where to mount a switch - i used a dual 2 pole, so in the middle it does nothing..
      Attached Files
      jUst plAythAtbEAt

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      • #5
        I did this mod ~5 years ago and used the synth a sum total of, NEVER. I guess this was one of those projects that never ended up being used in a track. I see it in it's box regularly, and never bother my ass playing with it, due to that issue with lack of MIDI.

        Highly Liquid are now kinda gone, but they did make something 'universal' to add MIDI to matrix-scanning keyboards, like the CS01, before they called it a day. You can get Your own board made from their instructions and BOM, or hunt one down on ebay, or see this:

        https://www.pharmasonic.jp/shop/inde...roller=product

        The Pharmasonics also nicely include the elusive manual and guide for installing to various machines as downloads.

        I opted for an ebay version of the UMR-2 as i could use PayPal.. The install in pending - NOW WE WILL SEE!!!!
        jUst plAythAtbEAt

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