[sdiy] square to sine

[David G Dixon]

> I've looked at V to F to a square, then integrating to a 
> triangle - but the amplitude of the triangle varies with frequency.
> Sure, you could correct for that with an AGC, but then your 
> fast tracking is lost.

No, because I'm going to use two 2164 expo converters: one for the V/F
converter, and one for the integrator, both controlled by the same voltage
(remember, 2164s pass bipolar current).

> I still think that the traditional integrator is the way to 
> go! if you want to stay analog.
> Wanting audio rate modulation rules out a lot of approaches.

> In my experience, it's easy to get a suare wave, and easy to 
> convert a square to a triangle, but impossible to convert a 
> variable frequency square to a fixed amplitude triangle 
> (which you need, if the tri to sine is to work.). Unless you 
> multiply by F, perhaps...

As with so many things, it's easy with 2164 VCAs.