[sdiy] Student projects from my Spring 2008 class posted

[Magnus Danielson]

Tom Bugs wrote:
> Hi Aaron
> 
> 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.
> 
> 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. (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.

On the same time, it is good that there is a current limiting in the 500 
resistance to the 4069. However, this causes interesting feedback-loops 
and they are also direction sensitive. Using a separate 4069 with the 
same type of resistive powering BUT NOT THE SAME is very likely to give 
a very different result.

A worthy common class project would be to build a complete 4069UB only 
synth. :D

Cheers,
Magnus