[sdiy] square to sine

David G Dixon dixon at mail.ubc.ca
Wed Oct 10 18:54:37 CEST 2012

> Integrator errors or temperature dependencies in David's 
> proposed circuit won't affect the output frequency, only the 
> output sine quality (well, triangle amplitude which will in 
> turn affect sine quality).  Right?

Right.  Sine shapers require triangle feeds of a certain amplitude, and if
that amplitude varies, the sine gets distorted (it either gets more
triangular or more square).  However, if I use reasonably fast opamps for
the integrator (TLE2072 is my preferred model here, with a minimum slew rate
of 35V/us) then I don't expect any issues until well above the audio range.

> Probably any modern "V-F" converter is going to use a charge 
> pump or something like that which would be more accurate at 
> tracking than a traditional synth-style VCO core.


> Thanks, guys for the insightful discussion!  I'm really 
> learning a lot from your comments as a relative beginner.

You definitely came to the right place.  Don't forget to have a look at the
archives as well (Google "Synth DIY archives").

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