[sdiy] Triangle-to-saw conversion

[Oren Leavitt]

Aaron Lanterman wrote:
> Is there a "canonical" example of triangle-to-saw conversion?
> 
> Saw-to-triangle is pretty easy to explain, but the other way around is trickier.
> 
> - Aaron
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 


Hi Aaron,

A common way is to level shift the triangle wave to 0 - 5V, and use a 
FET switch, that is driven from the square wave output of the tri osc 
comparator, to switch the saw output amp between operating as an 
inverting unity gain amp to a non-inverting unity gain amp.

It is non-inverting as the triangle ramps upward, then becomes inverting 
when the triangle reaches its top peak. The result is suddenly the +5V 
top of the triangle is now at -5V. As the tri osc is now ramping 
downward, the inverted result is ramping upward from -5V. When this 
reaches 0V the input from the osc is also reaching 0V and it changes 
state, switching the saw amp from inverting back to non-inverting. The 
saw output appears to be continuing upward past 0V to +5V again.

An example is the Eletronotes "ENS-76 VCO option 2". There are probably 
other examples that others may be aware of.