[sdiy] Electronotes, op-amp substitution, thru-zero oscillator...

[Grant Richter]

>
> most of the circuits show older op-amps, and there's some info on  
> substitutions, but there's still some holse.  specifically, i'm  
> wondering about what to use for the lm307s in the Random source  
> option 2... and more generally, what characteristics (in order of  
> importance) should i be concerned with matching when choosing  
> modern equivelents of older ICs?

Just use a TL07x op-amp in place of anything except a CA3130 or CA3140.

>
> i'm also looking at the thru-zero VCO... pretty complex project,  
> but i'll never be buying one from cyndustries... any of you  
> oldtimers ever build one of these beasts?
>

I built a quadrature thru-zero oscillator for panning the JAG using  
an LM13700 and MAX365.
They are nice for panning because they reverse direction correctly  
when you run the control thru-zero.

The quadrature waveshaper is here:

http://www.musicsynthesizer.com/Waveshapers/quadrature.html

Just sum the quadrature triangles to make trapezoids.

What good all this is in the audio realm I don't know? FM still  
sounds like FM always did.