[sdiy] Student projects from my Spring 2008 class posted

[Aaron Lanterman]

On Aug 23, 2008, at 9:59 AM, Tom Bugs wrote:

> Thanks for sharing those - there's some really interesting projects  
> (the Pitch to Voltage caught my eye in particular) - sounds like a  
> really inspiring course.

Thanks!

> I wondered whether the Scream Machine problems (or the cause of its  
> unstable wonder, perhaps?!) may be the powering of the CD4069. It  
> seems like the design realises that the CMOS chip has a max supply  
> voltage  of 18v, hence the resistors R29-32, but maybe that isn't  
> the most stable way to get a +/- 7.5v supply for it.

I'm pretty sure that's it. I knew when I saw the schematic that that  
looked iffy. Someone on the list - I can't remember who - suggested  
that the "weak" power supplied to the 4069 probably results in what he/ 
she called "motorboarding" effects.

> (surely 10u bypass caps should be added at least?). I think there  
> are some Buchla (or clone) schems for LPG floating around that show  
> a simple way to get a stable supply, but I can't locate them right  
> now.

He uses op amps to get +/- 6V in the Buchla 259 timbre generator.

- Aaron