[sdiy] Ultrarough draft of my hot-rodding of the Music Easel ringmod

[Aaron Lanterman]

On Nov 27, 2008, at 9:48 PM, Scott Gravenhorst wrote:

>> This may be a stupid question, but does anyone use XR2240 or  
>> ICL8038 to
>> build actual VCOs for modular synths, and if not, why not?
>
> Out of the box, if you use the datasheet circuit, neither part has  
> very good linearity with respect to a pitch CV.  Thomas Henry (I  
> think) has a novel circuit using a 8038 from just a negative supply  
> instead of bipolar.  He put it in the feedback loop of an opamp to  
> linearize it's response to pitch CV and it's supposed to work pretty  
> well, but the circuit is _linear_ CV, not expo.  As a side benefit,  
> this circuit allows the IC to run cool because it runs at half the  
> normal voltage.

I think there's an expo circuit using a 8038 somewhere in  
Electronotes. One of my students built various 8038 circuits, and  
didn't seem terribly thrilled with the chip. I don't think he had  
quite the debugging/tweaking experience to really get the most out of  
it though.

- Aaron