[sdiy] TR707 to TR77 voice triggering

cheater cheater cheater00 at gmail.com
Sat Nov 20 10:05:32 CET 2010


On Sat, Nov 20, 2010 at 02:55, Adam Inglis <21pointy at tpg.com.au> wrote:
>
> 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

yeah, that could probably work! I guess you want some sort of
buffering.. don't ask me, I'm no electronics wiz ;-)

Also, since there are 64 levels (thanks for pointing that out guys,
schematics show that there's actually a 6-bit DAC there..) I suggest
just one output.

Cheers,
D.

>>
>> 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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