Syncable VCLFO

jorgen.bergfors at jorgen.bergfors at
Thu Mar 26 13:19:30 CET 1998

>> Does anybody have schematics for a voltage controlled low frequency
>> that can be synced to the gate signal? That is, everytime you play a note,
>> triangle wave should start from zero, go upwards and the continue from that.
>> haven't seen this feature on any of the modulars around (Formant etc...). Of

>> course, a free running mode should also be available.  Preferrably a sine
>> output too.  

>E.G. Roland 100M has such an LFO.

>Take an existing circuit.
>Then simply add a discharge switch (cmos, mosfet, bipolar) parallel to the
>timing cap.
>The switch can be controled by a simple monoflop to enshure proper
>Interesting: Programable voltage to set the "initial point". In case of a
>generator some extra logic may be required to set up the proper charging
>after the sync.


Thank you very much, I will try this.
I think I will try it with the LFO circuit that is on the SSM 2024 data sheet. 
Another solution is to use one of my Doepfer PMS Quad VCO boards and change the 
timing caps to make them into LFOs. Actually Dieter Doefper drew a sync input 
on the schematics for me, when I bought it from him personally back in 1982. 
That was for oscillator sync on an ordinary VCO, but I suppose it should work 
at LFO-frequencies too.

Jorgen Bergfors

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