[sdiy] Adding "sync" to a Through-Zero Sinewave Oscillator design

[ulfur hansson]

following up on richie’s reply - thats a good start!

a quick max patch gave me a nice proof of concept, i think it has a nice sound to it - however it also revealed a potential problem.

if the sync input triggering exceeds the oscillation rate of the core, a loss of amplitude is introduced since the core can never reach its outer limits. i hadn’t thought of this before but it’s painfully obvious now!

some kind of expander circuit feels like over engineering, so perhaps this is not the best approach - unless I use some sort of logic gate trickery to only switch once the core has crossed zero at least once?

Sent from outer space

> On Sep 15, 2018, at 9:00 PM, Quincas Moreira <quincas at gmail.com> wrote:
> 
> Paging mr Ian Fritz......
> 
>> On Sat, Sep 15, 2018 at 6:33 PM Richie Burnett <rburnett at richieburnett.co.uk> wrote:
>> I guess the OP meant the frequency changes sign?
>> 
>> Homophones "sine" and "sign" in the same sentence always sounds confusing! 
>> At least we haven't had "sinc" and "sync" yet ;-)
>> 
>> -Richie.
>> 
>> -----Original Message----- 
>> From: Tom Wiltshire
>> Sent: Sunday, September 16, 2018 12:02 AM
>> To: ulfur hansson
>> Cc: synth-diy mailing list
>> Subject: Re: [sdiy] Adding "sync" to a Through-Zero Sinewave Oscillator 
>> design
>> 
>> I thought triangle oscillators didn’t change *sign*, but rather changed 
>> *direction*.
>> 
>> Changing sign would imply that a waveform at +2V would jump abruptly to -2V. 
>> Changing directions means only that a waveform that has been rising up to 
>> +2V would start falling instead.
>> 
>> > On 15 Sep 2018, at 23:26, ulfur hansson <ulfurh at gmail.com> wrote:
>> >
>> > hello list!
>> >
>> > i have been working on a prototype for a through zero quadrature sinecore 
>> > oscillator over the past few weeks, and have been thinking of ways to add 
>> > a novel type of "sync" to the circuit.
>> >
>> > I love the way traditional triangle core oscillator sync sounds, and much 
>> > prefer it to the harsher sawcore type sync.
>> >
>> > with trianglecore sync (I hope I understand this correctly) the waveform 
>> > changes sign at trigger points rather than doing a hard reset to 0v, 
>> > right?
>> >
>> > since my oscillator is through zero, my idea is to implement a switch that 
>> > inverts the incoming v/8 CV everytime the "sync" input exceeds a certain 
>> > threshold.
>> >
>> > this would (in my mind) effectively only change sign of the sine waveform, 
>> > emulating the triangle core sync i mentioned before.
>> >
>> > before I start gathering components and laying out a sync prototype board, 
>> > i'd love to see if any of you think this is a ridiculous idea - and if 
>> > there is any literature out there on various methods of sync, i would love 
>> > to learn more about it beyond discharging integrator caps to ground :)
>> >
>> > thanks so much for your insight!
>> > all the best,
>> > -úlfur
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> 
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> Quincas Moreira
> Synth Diy Guy
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