From: ricard@axis.se (Ricard Wolf)
Date: Wed, 16 Feb 94 08:12:27 MET

> Yes, by all means -- dig out that info on the variable synch and post it!
> Sounds like a useful mod to apply!

It's been a while, but here goes...

This is a mod for the sync circuit in the CEM 3340 data sheet, which permits
the sync 'level' to be varied from zero up to full hard sync, various
types of soft sync being acheived along the way. Sweeping the sync'd oscillator
with an LFO and using moderate amounts of sync creates a sort of
arpeggio, with different timbres at each note. It can also be used
for syncing a lower-frequency oscillator with a higher-frequency oscillator;
as you probably know, using normal hard sync, this just causes both
oscs to run at the higher frequency.


                                                                              
-------|                                                                      
 master|                                   -15V        
 3340  |                                    |         
 pin 8 |                                    |        
-------|                                    |       
   | (saw out)                             /       
   |                                     /C       
   |                                B |/         
 10 k pot <----- 470 pF -- 12k -------|               
   |                            |     |<             
   |  SYNC LEVEL                |        \E         
   |                            |  Any PNP \       
   |                            | transistor |    
  GND                           |            |   
                                |            |
                                |            |  
                                |         |---------------------- 
                               56 k       | pin 10 (tri out)     
                                |         |                     
                                |         |                    
                                ----------| pin 9 (soft sync in) 
                                |         |                     
                              0.1 uF      |   slave 3340                      
                                |         |----------------------
                                |                               
                               GND                             
                                                             
                                                            
Those of you who have the 3340 data sheet will recognize the sync circuit,
the component values are altered, don't think it matters much, I cut
this out from the schematics I made after I'd built the synth, so I think
it has more to do with what I had on hand...