[sdiy] function generation

[WeAreAs1 at aol.com]

In a message dated 11/8/03 9:39:54 AM, patchell at cox.net writes:

<< The 8038 is generally only suitable for pitch non-critical 
applications....in other words, not suitable for your main VCO.  The Terry 
Michael's (ASM-1) vco core is much more suitable for pitch 
generations.  However, there is nothing wrong with using the 8038 in other 
oscialtor applications.  You just have to keep in mind that it is not easy 
to make it an exponential oscillator. >>

Another reason not to use the 8038 is its huge current consumption.  Those 
suckers get hot!  

I do agree with Jim's wise suggestion to use the Terry Michaels-type VCO 
circuit.  However, noted DIY-guru Thomas Henry has figured out some workarounds 
for some of the 8038's notorious problems (poor pitch stability, limited control 
range, high current consumption).  He has published an article and schematic 
on his new 8038 VCO design at his website:   <A 
HREF="http://www.midwest-analog.com/diylvco.html">http://www.midwest-analog.com/diylvco.html</A>

I have not tried building this one, so I don't know how well it works.  
However, I do tend to trust Tom Henry on stuff like this.  Tom also seems to like 
using the old LM566/NE566 function generator in musical apps (although it has 
become rather difficult to obtain as of late).  See his website for more info.

BTW, did you know that the old Pollard Syndrum (circa late 70's) used an 8038 
as its drum tone oscillator?  Yeah, I know... a drum synth is not necessarily 
a pitch-stability-critical application, but it's definitely a musical one.  
The 8038's sine wave would be good for making drum ones, no?

Having said all that, I'd still go with the Terry Michaels VCO, though.

Best regards,
Michael Bacich