Oscillator sync?

[gstopp at fibermux.com]

     A synthesizer VCO is almost universally composed of the following 
     circuit sections:
     
     Voltage-to-current converter
     Integrator
     Reset comparator
     
     The voltage-to-current converter is used to change the charge on the 
     main oscillation capacitor in the integrator. (The conversion can be 
     linear or exponential, but the exponential type is more common and 
     produces musical intervals out of equal changes in voltage input, 
     which many people consider to be more useful.)
     
     The integrator's main oscillation capacitor is the "heart" of the VCO, 
     as a buffered version of the voltage on this cap becomes the VCO's 
     main waveform output.
     
     The comparator watches the voltage on the integrator cap and resets 
     the cycle when one waveform has been completed.
     
     If the VCO is the sawtooth-discharge type, the comparator simply 
     shorts out the cap for a tiny instant to produce a sawtooth wave.
     
     If the VCO is the triangle-square type, the comparator reverses the 
     direction of the charging current to produce a triangle wave. The 
     direction signal can be used as a squarewave output as well.
     
     Okay fine so far. That describes the basic VCO operation. Now it is 
     possible to bring in an external sync signal to reset the VCO cycle. 
     There's three main types of sync - "hard sync", "soft sync", and 
     "phase-locked" sync.
     
     "Hard sync" means that the signal brought in on the sync input causes 
     the integrator cap to be discharged, regardless of where it is in its 
     cycle.
     
     "Soft sync" means that the sync input causes the integrator cap to be 
     reset (or triangle direction reversed) if the integrator cap is 
     somewhere near the end of its cycle. If the cycle isn't close to being 
     reset in the first place, the sync input is ignored.
     
     "Phase-locked sync" means that the sync signal's frequency is compared 
     to the VCO's frequency (with a multiplier for example) and the 
     resulting error voltage is fed back around to the VCO's CV input 
     secion to cause the VCO to try to track the sync signal.
     
     Hard sync only really works if the VCO's frequency is higher than the 
     sync input's frequency. If the sync signal is a higher frequency than 
     the VCO frequency, the VCO frequency will just match the sync signal 
     except at lower amplitude. When the VCO is swept way above the sync 
     signal's frequency, the VCO's output will be a cool buzz-saw type of 
     sound, useful for electric guitar distortion-type sounds.
     
     Soft sync and phase-locked sync cause a mellower frequency locking 
     effect, allowing two VCO's to be tuned together beat-free. Hard sync 
     can be gradually transformed into soft sync as the sync signal's level 
     is reduced.
     
     Example synthesizer sync types:
     
     Hard sync - ARP Odyssey
     Soft sync - Emu modular
     Phase-locked sync - Moog 921B VCO's
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Oscillator sync?
Author:  "Berry R. Thrailkill" <bthrail at comp.uark.edu> at ccrelayout
Date:    4/19/96 11:09 AM

   Does anyone out there have a reasonably idiot-friendly explanation of 
how to sync two oscillators?  I've been playing with the sync feature on 
my little Moog MG1 and I'd like to incorporate oscillator sync into the 
monosynth I'm eventually planning to build...