[sdiy] Tri-core oscillator sync

[Tim Ressel]

Interesting.

I'm using a window comparator and a D flip flop to do the switching. The 
comparators drive the set/reset inputs and the hard sync drives the 
clock input. As I understand it this is reversing sync. My soft sync 
drives the reference input on the upper comparator on the window 
comparator, thus shifting the upper trigger point.

My design has the cap voltage bouncing between two positive points. If I 
add A reset FET the cap voltage will go to zero which is below the lower 
set point. Do your designs have the cap voltage going to zero as a 
matter of course?

--TimR

On 12/18/2018 10:47 AM, David G Dixon wrote:
> The way I have done this will all my tricore VCOs (including Dixie, Rubicon,
> and Atlantis) is to apply the syncing signal to the threshold of the tricore
> comparator for "soft" (reversing) sync, and to apply a sync-derived pulse to
> a JFET across the integrator capacitor for "hard" (resetting) sync.  This
> seems to work well.  I prefer the resetting sync sound in tricore VCOs
> myself.
>
>> -----Original Message-----
>> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On
>> Behalf Of Michael E Caloroso
>> Sent: Monday, December 17, 2018 9:44 PM
>> To: Tim Ressel
>> Cc: SYNTH DIY
>> Subject: Re: [sdiy] Tri-core oscillator sync
>>
>> "Hard sync" means that the charging core is prematurely reset
>> by an external trigger.  It is intended to create a complex
>> waveshape with altered harmonics.  By altering the frequency
>> of the sync'd VCO above that of the master VCO, you sweep the
>> harmonics.
>>
>> "Soft Sync" means the slave VCO is oscillating at the same
>> frequency of the master VCO.
>>
>> MC
>>
>> On 12/17/18, Tim Ressel <timr at circuitabbey.com> wrote:
>>> Hi,
>>>
>>> I have made a triangle core oscillator that works really
>> well except
>>> for the sync. I implemented what I thought would be hard
>> and soft sync
>>> but the results were disappointing. As I understand it my
>> "hard sync"
>>> is known as "reversing sync" i.e. a rising edge causes the steering
>>> flip flop to change state and thus the wave reverses. My
>> "soft sync"
>>> changes the upper set point on the window comparator.
>>>
>>> I would like the soft sync to sound like the Doepfer A-110-2
>>> oscillator soft sync if possible.  Thoughts?
>>>
>>> --
>>> --Tim Ressel
>>> Circuit Abbey
>>> timr at circuitabbey.com
>>>
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>
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-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com