[sdiy] Pro One CEM3340 Sync magic

[MTG]

And it appears there is a negative side effect of doing this. When you have 
an external clock, the first note in the arpeggiator will sound when you 
turn on EXT mode. When the first external clock actually arrives, the synth 
will play the second note. :-P  For some reason the sequencer is not 
similarly tainted.

GB
www.musictechnologiesgroup.com


----- Original Message ----- 
From: "MTG" <grant at musictechnologiesgroup.com>
To: <Synth-diy at dropmix.xs4all.nl>
Sent: Saturday, April 17, 2010 6:03 PM
Subject: [sdiy] Pro One CEM3340 Sync magic


>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
>
> GB