[sdiy] TR707 to TR77 voice triggering

Stewart Pye stewpye at optusnet.com.au
Thu Nov 18 21:03:53 CET 2010


I agree that it would be more versatile to have positive going triggers 
coming out of the TR707, however I'd replicate ENV GEN circuit for each 
voice but leave out the decay capacitor. I think I'll layout a PCB to do 
this for my 707. It's only 2 x LM324, 8 transistors and 16 resistors.

Also, there's more than 2 levels of accent. 64 I think, but most are 
only accessed via MIDI.

Cheers,
Stew.

cheater cheater wrote:
> Hi Adam,
> no sweat, I didn't read anything on digital electronics other than a
> few wikipedia articles and I basically understand what's going on.
>
> 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.
>
> 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. How to lay out the usage of the accent on
> the panel is a fairly creative process and you can do a lot of
> interesting things with it.
>
> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>               
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>>     
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
>
>   




More information about the Synth-diy mailing list