[sdiy] Roland CR-8000 triggering

Richie Burnett rburnett at richieburnett.co.uk
Sat May 23 19:26:51 CEST 2015

I guess the *logical* way to do it would be to use an AND gate on each instrument trigger line between the cpu board and the voicing board, to combine the logic outputs from the CR-8000's own cpu and those from your trigger board.

An AND gate will give a low output level if either of its inputs goes low.  Therefore you should be able to trigger each voice either by the CR-8k's own CPU or via your new trigger board. It does require an AND gate for each instrument though, but you get four in a chip.

There may well be some cheaper way of doing it, but that's the method I would investigate. Hope this helps :-)


Sent from my Xperia SP on O2

---- Adam Inglis wrote ----

>I'm looking at installing a midi to trigger interface in my CR-8000,  
>but I  want to retain the internal trigger function. I need a way of  
>isolating the two trigger sources from each other.
>The internal trigger system is from the CPU, via some pull-up  
>resistors and a buffer, giving negative-going triggers from 5 - 0  
>volts, seen in this pic here
>These triggers go to the various analogue voice circuits, here's a  
>couple of examples, bass drum and hand clap
>I tried duplicating the input capacitor seen at the trigger entry in  
>these voice circuits, for each trigger source, however this attenuated  
>the  pulse too much resulting in a different voicing (proving that  
>these circuits can be "velocity" or voltage sensitive).
>Elby Designs, who make the MIDI2SDS16 interface that I'm testing, say  
>that in general you can't have both connected at once.
>Any thoughts?
>(BTW, Roman asked re a previous post whether there was any change of  
>voicing with pulse width variation. In the first pic you can see they  
>quote a huge range of variation as the width varies with the tempo,  
>from 4 - 70 milliseconds. So I guess the pulse width can't be  
>critical. I haven't tested below 4 ms though.)
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