[sdiy] Elektor Formant Re: Test / Sequencer / Arduino

Thu Mar 26 11:40:03 CET 2015

Hallo Harald,

More good werk on the Formant!

And yes indeed, changes in the 5V indeed influence pitch. However, the specs of the uA723 
voltage regulator used to obtain the 5V are that there is a typ. 0.003% change in the 
output voltage per degree C, the REF02 spec is 20 ppm (for the C variety), which 
translates to 0.002% change per C, if I calculated correctly? If I calculated that right 
there may not be a big gain in using a REF02? The uA723 is not a bad part.

My Formant DOES have some coupling of the generated signals: you can sometimes hear a soft 
whine in the output signal even when it should be silent. It could well be that this is 
via a power line somewhere! C4/680n on the 5V line is pretty far from the V++ pin of the 
schmitt-trigger, I may try adding another one to see if I can get rid of that whine.

Another drift factor could be that the threshold of the 7413 or the LS7413 varies with 
temperature... Yes, it does. Both Umin and Umax vary with temperature. Hmm. Perhaps it 
would be better to use a good opamp comparator in a new design.

I like the sync addition!

And a nice looking board it is too. The original VCO board is far too big, it would have 
been nice if it was 2 separate eurocards in the first place. But I guess they preferred a 
board where people could make no mistakes.

Thanks, I will read your site more later.

rick

On 26/03/2015 10:24, Harald wrote:
> Hallo Rick,
>
> for your resting uA726 this might be of interest:
> http://www.haraldswerk.de/NGF/NGF_VCO_CORE_ONE/VCO_CORE_ONE.html
> I have rebuild the Formant VCO with some modern parts keeping the
> overall architecture original.
>
> Harald
>
> Am 25.03.2015 um 14:50 schrieb Rick Jansen:
>> hi Carsten,
>>
>> Great work! Its clearly visible you put a lot of work and effort into
>> your Formant. How did you make the white front panels by the way?
>>
>> I've always wondered who C. Chapman is. In some web pages he's referred
>> to as "Cyril Chapman", as "Colin Chapman" in others. I seem to remember
>> someone from Elektor mentioned the name is a writers name, but he could
>> not recall the authors true name. Or perhaps it was C. Chapman himself
>> who told me :-)
>>
>> The Formant is from 1977, some parts now *really* are hard to get, 38
>> years later... The uA726 is scarce, older Moog mini's and Memory Moogs
>> use them too, and they are sought after as repair parts. The CA3084 PNP
>> array may be hard to find, and the CA3080 OTA's are getting rare too.
>>
>> All in all, building a Formant is a project only undertaken by the
>> brave. Or was it the foolish?
>>
>> As for the sequencer: I'm going to try if it is feasible to finish it by
>> replacing the oldfashioned digital circuits by an Arduino Uno (14
>> digital I/O pins). Perhaps even an Arduino Mega, which has even more
>> digital I/O pins (54!).
>>
>> Best, and thanks for the links!
>>
>> rick
>>
>>
>> On 25/03/2015 12:18, Carsten Toensmann wrote:
>>> Hi Rick,
>>>
>>> when I started my own Formant project (MSS2000) I read your pages of
>>> course
>>> to get an impression of what it could mean to start such a huge
>>> project. And
>>> yes - it was a LOT of work, but it was worth it. I never built a
>>> sequencer
>>> for it though but a MIDI interface.
>>>
>>> Nowadays it seems to me that the Formant disappeared from the DIY
>>> scene more
>>> or less, which is a pity in my opinion, so I hope you will manage to
>>> reanimate your system and continue your project.
>>>
>>> I finished my Formant project in May 2008 after a building time of 6
>>> years.
>>> The system has been part of several music productions and I like it. See
>>> details on http://www.analog-monster.de/tagebuch_en.html
>>>
>>> Regards
>>>
>>> Carsten
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: synth-diy-bounces at dropmix.xs4all.nl
>>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] Im Auftrag von Rick Jansen
>>> Gesendet: Mittwoch, 25. März 2015 11:38
>>> An: Synth-Diy
>>> Betreff: [sdiy] Test / Sequencer / Arduino
>>>
>>> Hi,
>>>
>>> This is both a test message and a new-old project revival note. I was
>>> notified traffic on synth-diy may have halted, but as far as I can see
>>> everything still works.
>>>
>>> For the Formant I was, years ago, designing and building a sequencer,
>>> as we
>>> all do one time in our life. This one is inspired by the Synthanorma
>>> Sequenzer, as used by Kraftwerk and Tangerine Dream, in that it does not
>>> have potmeters but uses 12-position rotary switches.
>>>
>>> Mine has 3 rotary switches per step: 1. note duration 2. octave, 3.
>>> pitch. A
>>> switch, a trigger output and a LED (to impress the ladies) are also
>>> included.
>>>
>>> I was in the process of doing a circuit built with the regular HC digital
>>> ic's, like timers, counters, multiplexers etc etc, and a DA-converter.
>>>
>>> Basically the circuit already work[ed][s], but you know how it is when
>>> duty
>>> and jobs and relatinships take their time: such projects get shelved.
>>>
>>> For years I've seen projects in magazines like Elektor, using small
>>> digital
>>> controllers like Arduino. Usually I skipped those, as that is not the
>>> kind
>>> of electronics I personally like a lot. But I realise now how cheap and
>>> versatile they have become. They're almost a uA741. Perhaps even more
>>> Arduino's are sold than uA741's these days. And, with analog in/out, and
>>> digital in/out pins. Impressive.
>>>
>>> I even saw that is is quite easy to sync an Arduino program with the MIDI
>>> clock!
>>>
>>> Here is the current status:
>>>
>>>     <http://dropmix.xs4all.nl/rick/Emusic/Sequencer/>
>>>
>>> Now I need to bring back to life the Formant, which has been sitting
>>> there,
>>> unused for about 10 years. Hope the elco's are all still keeping their
>>> liquids!
>>>
>>> Best,
>>>
>>> rick
>>>
>>>
>>> _______________________________________________
>>> 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
>>>
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>