[sdiy] TR707 to TR77 voice triggering

Adam Inglis 21pointy at tpg.com.au
Sat Nov 20 02:55:41 CET 2010


On 18/11/2010, at 7:55 PM, cheater cheater wrote:

> My suggestion is to make a standard output from those 707 triggers, so
> that they have a positive-going pulse, of adequate voltage (+5V). Then
> make standard inputs on your 77. This is a bit more complicated but
> having a set of standardized inputs and outputs on things you own is a
> very good idea and you'll thank yourself later.


I think you're right. My view of this needs to broaden a bit. It then  
can contribute to the whole studio, as in a "modular" system


> You can have two separate inputs for the two separate levels of
> accent. Then you can use those somehow in your 77, which could have
> two separate inputs as well.

That's an interesting idea I hadn't considered - having a global  
accent input for the 77s voices

Maybe implementing it like the envelope circuit in the 707 - i.e. as  
a common rail for the trigger transistors




>
> On Wed, Nov 17, 2010 at 09:58, Adam Inglis <21pointy at tpg.com.au>  
> wrote:
>
>> More tests today -
>> the negative going triggers from the latch chips do indeed manage  
>> to trigger
>> the 77s voices, but only very quietly and without accent.
>> Unfortunately, the positive CVs from the envelope generators are  
>> unsuitable
>> as trigger sources - I discovered any rapid sequence of notes  
>> causes a
>> slurring of the envelope, especially with accent, so not all notes  
>> are
>> reliably converted to triggers.
>>
>>
>>
>> regards
>> Adam Inglis
>> http://www.adambaby.com
>>
>> On 16/11/2010, at 9:42 PM, Adam Inglis wrote:
>>
>>
>>> er.. I'm not yet actually up to the chapters on logic in  
>>> Horowitz&Hill, ha
>>> ha!!
>>>
>>> You're right - there are negative triggers to be found in the 707  
>>> (+5 to
>>> ground) going to the bases of each transistor in each envelope  
>>> generator.
>>> The Accent line is a positive CV line going to all the collectors  
>>> of these
>>> transistors, can't remember the levels, prob around 5 volts  
>>> (there are two
>>> levels of accent).
>>> Not sure - does that sound like something I could AND??
>>>
>>> On 16/11/2010, at 6:11 PM, cheater cheater wrote:
>>>
>>>
>>>
>>>> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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