SergeModular

Hi James,

thanks much for this explanation! Do you think it is possible to post a short sound file of
just an [NTO] square wave being hard-sync'd and being slowly tuned from unison upwards
(relative to the sync source oscillator), so that we hear the humps as well as the sync
sound? Hope this is possible, as it would really be instructional before attempting to
modify.

Best regards,
thanks in advance,
Jan-Hinnerk

--- In SergeModular@yahoogroups.com, "James R. Coplin" <moog@q...> wrote:
> I can try a little. At first, removing the resistor completely made the osc
> much more receptive to resets, super hard sync with no effort. Any kind of
> an edge would be enough to reset the osc. However, *anything* would also go
> directly into the core via the reset circuit: DC, noise, the evil eye, etc.
> It was fairly easy to get "odd" behavior besides the desired reset. It was
> just too sensitive, any positive short voltage would reset the core, often
> when you didn't want it to.
>
> This is why Ken recommended putting at least a small value resistor to
> provide protection for signals leeching in that were not intended to reset
> and provide sync. This worked better at removing the oddness in having the
> wire and provided a degree of input protection for the core.
>
> Going on the "if a little is good, more is better approach", I started
> increasing the value of the resistor to see what the largest resistor (ie,
> closer to the osc. design spec) that would work and provide hard sync
> behavior would be. 3k seems to be about the largest value that still lets
> the core get reset by strong edges while providing an adequate buffer
> against the external world. It is enough to block nearly all the DC, misc
> noise, etc. that could impact the stability of the osc. So far so good...
>
> However, a lot of this is personal preference. The 3k resistor is not super
> hard sync. It is kind of a medium-hard sync. You could use a lower value if
> you want the reset touchier. All of this being said, it is not perfect.
> There are noticeable humps when the two osc are close together. The sync
> circuit was not designed for hard sync, so you are getting part of the
> behavior (enough to satisfy me at least) but not perfect behavior. I find
> that you need to offset the freq of the slave osc to stop the humps and keep
> the modulations from ending near the next freq crossover. Within these
> ranges, it works lovely.
>
> Again though, this works fine for me (I've converted all of mine and don't
> have any problems) but it is not a STS sanctioned, blessed, or recommended
> mod. It does change the circuit (although slightly) and has not gone through
> the rigorous bench testing that a STS sanctioned change would have to go
> through.
>
> Bottom line, if you really want hard sync (and I did) this is probably the
> only option you have as a STS change in the osc to accommodate hard sync is
> unlikely. Later!
>
> James R. Coplin
> ***************
> If anyone asks of my whereabouts,
> simply tell them i've gone out the window
> for a spot of tea and am not
> expected back any time soon.
> ***************
>
> > -----Original Message-----
> > From: metafoetus2002 [mailto:jan-hinnerk.helms@t...]
> > Sent: Tuesday, January 18, 2005 7:38 PM
> > To: SergeModular@yahoogroups.com
> > Subject: [SergeModular] Serge Sync
> >
> >
> >
> > Hi,
> >
> > last December we saw some posts regarding modification of the Serge [PCO]s
> > and [NTO]s
> > from Soft Sync to Hard Sync.
> >
> > James R. Coplin suggested to replace the 22k Ohm resistor on the Sync
> > input with a blank
> > wire.
> > Then Ken Stone suggested to replace the 22k Ohm with a 220 Ohm for circuit
> > protection.
> > One month later James suggested to replace the 22k Ohm with a 3k Ohm for
> > "best sound
> > and minimal (note I didn't say none) core effects".
> >
> > I am very thankful and excited about this possibility to get hard sync on
> > my Serge. Now I
> > wonder if someone of the more electronically knowledgeable guys on this
> > list could be so
> > kind and explain
> > - the possible core effects
> > - what's the trade-off between circuit safety and hard sync sound
> > - why the difference between soft and hard sync is just changing a
> > resistor
> >
> > Thanks much in advance,
> > best regards,
> > Jan-Hinnerk
> >
> >
> >
> >
> >
> >
> > Keep on Patchin'!
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >