[sdiy] Roland CR-8000 triggering

Adam Inglis 21pointy at tpg.com.au
Sun May 24 01:24:52 CEST 2015


Many thanks for all the replies , and Nick, thanks for the schematic.

I guess, as Laurie points out, what I want would mean having digital  
and analogue signals on the same bus!
A feature of the MIDI2SDS that I am hoping to exploit is that the  
trigger pulse amplitude is proportional to midi note velocity. I need  
to do more tests but I think the CR voices may respond quite nicely to  
this.
Unfortunately many of the suggestions would defeat this response.

Looks like it's going to be a case of either/or ... so some kind of  
switching between the two control options will be needed.

cheers
Adam

On 24/05/2015, at 3:26 AM, Richie Burnett wrote:

> 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 :-)
>
> -Richie,
>
> 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
>> http://www.adambaby.com/images/tech%20pics/CR8000/CR8k_CPUtrig.png
>> These triggers go to the various analogue voice circuits, here's a
>> couple of examples, bass drum and hand clap
>> http://www.adambaby.com/images/tech%20pics/CR8000/CR8k_BDtrig.png
>> http://www.adambaby.com/images/tech%20pics/CR8000/CR8k_claptrig.png
>>
>> 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?
>>
>> cheers
>> Adam
>>
>> (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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