[sdiy] Formant filters, yay!

Till Moses Kammertöns till at kammertoens.de
Tue Mar 14 00:32:33 CET 2017


Rob Hordijk recently released an oscillator that does what he calls “masked sync” — it’s basically VOSIM, where the syncing oscillator is a downward sloping saw and the synced oscillator is a triangle that can be “nudged" (via CV) towards a downwards sloping saw, too (so at sub audio rates it can excite a filter etc).
There is also a square sub oscillator one octave below the syncing oscillator that can modulate the frequency of the synced oscillator, giving the impression not one but two formants (quite clever idea) where the modulation depth determines the distance between the two formants.
He couples the whole thing with a S&H that gets triggered by the syncing oscillator and has the synced oscillator at the input, and that is normaled to the mod inputs of both oscillators. At sub audio rates this can generate chaotic patterns and at audio rate you can generate noise and many sounds in between. See here:

https://www.youtube.com/watch?v=tbNcEiPu06M <https://www.youtube.com/watch?v=tbNcEiPu06M>
https://www.youtube.com/watch?v=lE0pTZJgQrg <https://www.youtube.com/watch?v=lE0pTZJgQrg>
https://www.youtube.com/watch?v=62dW_S8kqhg <https://www.youtube.com/watch?v=62dW_S8kqhg>

Here you can find a signal flow schematic:

http://hordijk-synths.info/news/2016/08/28/osc-sync.html <http://hordijk-synths.info/news/2016/08/28/osc-sync.html>

Best,
Till

> On 13 Mar 2017, at 23:42, Jarno Verhoeven <jarno.verhoeven at ziggo.nl> wrote:
> 
> 
> Speaking of VOSIM, apparently there's an analog implementation of it.
> Haven't managed to find a schematic of it.
> Has anyone found a schematic for a VOSIM osc (analogue )?
> Regards, Jarno 
> 
> 
> Verzonden vanaf mijn Samsung-apparaat
> 
> 
> -------- Oorspronkelijk bericht --------
> Van: Tom Wiltshire <tom at electricdruid.net> 
> Datum: 13-03-2017 20:17 (GMT+01:00) 
> Aan: Quincas Moreira <quincas at gmail.com> 
> Cc: *SYNTH DIY <synth-diy at synth-diy.org> 
> Onderwerp: Re: [sdiy] Formant filters, yay! 
> 
> Also relevant to the ancient VOSIM technology element of this thread:
> 
> http://steamsynth.com/shop/moog-unit-modules/scat-talker-mu-model-1420/ <http://steamsynth.com/shop/moog-unit-modules/scat-talker-mu-model-1420/>
> 
> Based on the Votrax SC-01 chip, which I haven't heard of, but it's not my field. Certainly turned up in enough places during its era.
> 
> Tom
> 
> On 13 Mar 2017, at 17:18, Quincas Moreira <quincas at gmail.com <mailto:quincas at gmail.com>> wrote:
> 
>> This filter and the Vowel patch shown may be relevant to this convo :)
>> 
>> 
>> https://www.youtube.com/watch?v=4YANHwTzAzo&t=42s <https://www.youtube.com/watch?v=4YANHwTzAzo&t=42s>
>> 
>> On Sat, Mar 11, 2017 at 8:05 PM, <rsdio at audiobanshee.com <mailto:rsdio at audiobanshee.com>> wrote:
>> 
>> On Mar 11, 2017, at 1:23 AM, Tony K <weplar at gmail.com <mailto:weplar at gmail.com>> wrote:
>> > All this talk of vocal filters made me nostalgic for S.A.M. in the Apple ][+ playing through a 1408 DAC board.
>> > I don't have have Chamberlain's MAM anymore but I believe there was  a good coverage of the topic in there . I seem to recall VOSIM software.
>> > Would have loved to know who wrote that original Apple program.
>> > The later Atari version of SAM was also good but never quite sounded as impressive or 'demented' as the Apple version. Used that as my first drum machine in phoneme mode.
>> >
>> > Sorry if this is completely irrelevant.
>> 
>> It seems quite relevant for DIY Synthesis - at least it was for my experience. It even seems relevant, still, in terms of today's embedded audio synthesis platforms.
>> 
>> The Apple ][+ community seemed to be 99% piracy. People had no qualms about photocopying the manual and duplicating the disks. I never actually did this for myself, because I never actually saw any original software packages, and yet people often volunteered to give me copies when I was young. The strangest was when someone copied the S.A.M. manual and disk for me, because I realized that the software was useless without the hardware.
>> 
>> Fortunately, the last few pages of the S.A.M. (Software Automatic Mouth) software has the schematic for their hardware. I hand-etched a double-sided Apple ][ peripheral card with the DAC and op-amps and managed to get the thing working!
>> 
>> The S.A.M. vocal synthesis was reasonably interesting, but I quickly found that I preferred writing non-vocal audio synthesis algorithms for myself. I ended up with a linear FM program that was quite impressive (but only one voice of two operators). The analog output was a couple of watts, so it could directly drive a large speaker without an amp.
>> 
>> I would also like to know who wrote the original Apple S.A.M. software. Perhaps I can find the ancient photocopy of the manual and look for the author's name, if it's even mentioned in addition to the software company name.
>> 
>> You are correct that Chamberlain's "Musical Applications of Microprocessors" includes a chapter that covers VOSIM. It's Chapter 13, Digital Tone Generation Techniques, in the final section for "other," and it literally stands for VOcal SIMulation. I never realized that VOSIM is related to FM - not in exact technique so much as similar processing complexity.
>> 
>> Later voice simulators seemed to be based on dedicated chips where there was no direct access to the DAC. By being exposed to S.A.M. and building the DAC board, I was able to learn a lot more about digital audio synthesis on my own (I didn't read MAM until decades later). Of course, several years later computers like the Amiga had 8-bit DAC features built in, and the Apple //gs actually included the Ensoniq ESP chip, but by that time I had moved on.
>> 
>> Brian Willoughby
>> Sound Consulting
>> 
>> 
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>> 
>> 
>> -- 
>> Quincas Moreira
>> Test Pilot at VBrazil Modular
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