[sdiy] Hard Sync on DCOs

[Florian Anwander]

Hello Tom


> Looking at the schematics, the JX-8P (not sure about the 3P, but I doubt it's different)
http://fa.utfs.org/diy/jx3p/schemo/JX3P_schematics_08_mainboard.jpg

> uses a 'standard' sync where the reset pulse from one osc is fed to the other. In this case, it's fed to the 8253 counter's reset input, but it's the same thing.
> Neither osc has a reset comparator which would enable it to produce a sync sound without the influence of the other osc.

Hm, I do not really understand your question. Hardsync on a saw-core VCO 
is: send the reset trigger (=output of the comparator) from the master 
oscillator to the switch (transitor) which resets the capacitor of the 
slave oscillator. There it will be OR'ed with the reset from the 
original Comparator

At a DCO there is no comparator, but there is the trigger from the counter.
Now at the JX3P/JX8P the signal from  the master oscillators counter is 
OR'ed with the the signal from the slave oscillators counter and then 
resets the capacitor.

In both cases the reset signal of the master is OR'ed with the reset of 
the slave. That is, what hardsync is. Hard sync does not work with the 
comparator input. That would be soft sync (see the Roland SH-7's 
oscillator B).

Florian