[sdiy] triangle hard sync

[cheater cheater]

yeah, or two diodes (rectifier). Doesn't sound so difficult.

But I think that's only a workaround and the original problem is that
you want to be able to change the state of the core to either exactly
rising or exactly falling, instead of only being able to swap it. So
maybe that's one thing you need to think about. I understand you'd
need to modify the part of the circuit the comparator feeds into (I
lost the schematics and I don't know what you're working off right now
anyways)

Cheers,
D.

On Fri, Jul 9, 2010 at 23:30, Stewart Pye <stewpye at optusnet.com.au> wrote:
> Hi David,
>
> Couldn't you just insert a diode in series with your sync signal?
> I think the TR808 bass drum does a similar thing, although I think they have
> the diode so that the schmitt trigger point does not affect the rest of the
> circuit it should achieve what you want also. Look around the VCO section of
> the bass drum schematic...
> http://www.kolumbus.fi/janne.husu/specs/909va.gif
>
> Regards,
> Stewart.
>
>
> David G. Dixon wrote:
>>
>> Hey Team!
>>
>> I'm trying to retrofit hard sync onto triangle-core LFOs so I can sync
>> them
>> with gates, triggers, square waves, etc.  I can get the triangle to reset
>> to
>> 0V with a JFET across the cap, but I also want the triangle to start in
>> the
>> upward direction every time as well.  I can just about achieve it if I put
>> sync spikes into the comparator reference voltage input, but the negative
>> sync spikes cause the triangle to reverse direction, which I don't want.
>> This wouldn't be a problem if the sync source is a sawtooth, but a square
>> or
>> a gate signal would always have negative spikes.  I suppose I could add a
>> rectifier to eliminate the negative spikes, but that seems too
>> complicated.
>>
>> I see that the Oakley VC-LFO does what I want, albeit in the wrong
>> direction.
>>
>> Also, I could probably rig it such that the triangle started at its most
>> negative point, in which case it would have to go up.  Perhaps I'll look
>> into that next (that might be better).
>>
>> In any case, if anyone knows how to do this, or can point me to a document
>> where I could learn about it, I'd sure appreciate it.  I believe that
>> Magnus
>> Danielsson had a relevant document, but the link appears to be dead.
>>
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