[sdiy] Pro One CEM3340 Sync magic

[Simon Brouwer]

Op 18-4-2010 3:03, MTG schreef:
> I had an interesting discovery this weekend (for me anyway). As I'm 
> sure many of you know, the Pro One has a single (free-running I call 
> it) LFO and this lone LFO also drives the sequencer/arpeggiator.  
> While working on my "replacement CPU" I noticed, that while the LFO 
> was free running, it would always sync to the user when they first 
> played notes with the Arp on. That is, the first note would sound 
> immediately and then the LFO would clock the next note one LFO period 
> later. My initial attempts at duplicating the arpeggiator resulted in 
> no note sounding until the LFO "came around" to the proper edge used 
> to clock the notes. So I'm thinking, how the hell do they reset the 
> LFO to the user?  Low and behold they used a rather clever method of 
> squashing the triangle wave of the 3340 which resets the LFO. This 
> seems to be somewhat undocumented since the part has other pins for 
> sync. Anyway I guess it's more well  known to others, since today I 
> found a mention of it in this thread:
>
> http://electro-music.com/forum/post-176134.html

Is it correct to say that the CEM3340 "sync" is not synchronization in 
the true meaning of the word, as it does not lock the frequency of the 
sync'ed oscillator's output to that of the syncing oscillator, as a 
saw-core hard sync does?

I remember it being discussed here that Roland used additional circuitry 
with the CEM3340 in the Jupiter 6 to achieve the same type of sync that 
the Jupiter 8 had.

-- 
Vriendelijke groet,
Simon Brouwer.