[sdiy] TR707 to TR77 voice triggering

cheater cheater cheater00 at gmail.com
Tue Nov 16 09:11:42 CET 2010


Hi Adam,
can't you use the trigger that goes into the 707's envelopes? I
believe there's a separate accent line (as far as I remember the
schematics). You can AND that with a separate copy of the trigger
lines, and add it to the original trigger lines. That's probably one
AND array, together with just some logic buffers or whatevers (I'm not
that great with digital logic hardware, just software!)

Maybe you can use those directly in the 77 without any conversion.

Cheers,
D.

On Tue, Nov 16, 2010 at 02:20, Adam Inglis <21pointy at tpg.com.au> wrote:
> Cheers - I was hoping to avoid building a negative rail, the 77 manages
> without one (The negative-edge detector circuits that make up the matrix
> generate a brief negative pulse on the falling edge of the square waves from
> the multivibrator counters).
>
> Hanging a common-emitter amp off the 24 volt rail to invert the signal, and
> running this into a similar edge-detector seems to work, but thats a lot of
> parts if I have to make one for every voice.
>
> regards
> Adam Inglis
> http://www.adambaby.com
>
> On 15/11/2010, at 2:37 PM, Chromatest J. Pantsmaker wrote:
>
>> I'm thinking a voltage regulator to get you your -7 volts.. and then a
>> transistor for each voice. use the 707 CV to trip the transistor
>> letting the -7 through?  Probably a current limiting resistor on each
>> one?
>>
>> Of course, this is how I design my own stuff... and sometimes it
>> works.  I really have no idea of the "correct" way to do things.
>>
>> On Sun, Nov 14, 2010 at 9:30 PM, Adam Inglis <21pointy at tpg.com.au> wrote:
>>
>>> Hi All
>>>
>>> First post - long time lurker and learner here for many years.
>>> Self-taught
>>> in analogue audio electronics thanks to a studio full of old "junk" from
>>> the
>>> 70s and 80s, an oscilloscope from the 60s, and the first few chapters of
>>> Horowitz and Hill!
>>>
>>> Question: Someone here mentioned not too long ago the idea of using the
>>> voice trigger signals in a Roland TR707 to trigger external instruments.
>>> It
>>> got me thinking, as I love the interface of this drum machine - quick and
>>> fun.
>>>  I would like to be able to trigger the voices in my old preset Roland
>>> Rhythm TR77. This uses passive LC voice circuits, which respond fairly
>>> dynamically to voltage triggers of between -3 to -10 volts. Looking at
>>> the
>>> 707, I found the voice group's envelope generators supplied a positive
>>> envelope CV of varying decay times and amplitudes (about 2-5 volts)
>>> depending on instrument. These CVs also respond to the 2 levels of
>>> programmable ACCENT, and so would appear to be a good source of
>>> triggering.
>>>
>>> Any suggestions as to a simple, low-parts-count circuit I could install
>>> (several iterations of) into the 77 that would convert the positive CVs
>>> from
>>> the 707 into brief negative pulses for the 77s voices?
>>> I should mention there is 0 - 12 - 24 volts available in the 77 with just
>>> basic filtering, no voltage regulators, so I was assuming it would need a
>>> transistor rather than a chip based solution.
>>>
>>> Anyone interested in my crude investigations into the workings of the
>>> TR77
>>> can have a look here...
>>> http://www.adambaby.com/studiotech_TR-77.html
>>>
>>>
>>>
>>>
>>> regards
>>> Adam Inglis
>>> http://www.adambaby.com
>>>
>>>
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>
>>>
>>
>>
>>
>> --
>> .sig
>> -Chromatest J. Pantsmaker
>> http://www.chromatest.net
>>
>>
>>
>
>
>
>
>
>
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