[sdiy] 4069 VCO to get started? My answer

[Nicolai Czempin]

Scott Gravenhorst wrote:

>Richard Wentk <richard at skydancer.com> wrote:
>
>> Laurie Biddulph wrote:
>
[..Snip...]

All this info is very interesting, and it sounds really clever to use 
something meant for digital in an analogue way. However, it does nothing 
to make it simpler.
Perhaps it is simpler to *build*, but not simpler to *understand*. I 
should have been clearer on that point, I guess.
In the meantime, I have built a basic VCO, with lots of limitations. At 
this stage there was enough debugging before I got any signal at all, 
and it's very exciting to finally get something on the scope. I even 
managed to get something to the loudspeaker, by simply connecting the 
saw out to a transistor.
For reasons I haven't fully understood yet, simply putting the LS where 
the scope used to be "kills the signal". My workaround did produce some 
sound on the speaker, and I was able to vary its frequency (just using a 
pot connected to +V and the input line. However, the output signal 
seemed to die after a while, not sure why. Disconnecting the LS, waiting 
for a few seconds and then reconnecting got the signal back, only for it 
to die again. Looking forward to understanding exactly why all this is 
happening.

In the meantime, I guess I need to finally dig out the soldering iron 
and build that little (pre-)amplifier kit I have.