[sdiy] Kraakdoos

[Metrophage]

--- Rafael_Cohen at prusec.com wrote:

> I have had my eye on the Cracklebox schematic for a
> month or two thinking to build it and I have a question about what
> parts to get...

You're lucky, as there are not many parts! It took me about a year to
get around to building this one,

> I poked around on Jameco and Mouser and it looks like there are many
> different versions of the BC547 and BC557 transistors.  Which one do
> y'all  use?  Why?

I don't use those. I am in the states, where the BC type transistors
are less common. They seem like general purpose NPN and PNP
transistors, so I just used the 2N3904 and 2N3906 which I had on hand.

 > Also 30+ hits for the 709 op amp.... Differences?  Preferences?

30 types of 709? Now that's scary. Since we're exploiting it's bad, old
school lack of frequency compensation, I decided older was better, and
got UA709HM amps of the TO5 type. This was kind of arbitrary though, I
have not tried any other types of 709. I'd find datasheets for
whichever brands you are finding, and look up the letter suffixes, to
see what characteristics are different. Still, this is just a
single-amp chaotic oscillator - I doubt if there is going to be much
difference. But who knows? I had to try several 709s before I found the
particular one i was happy with, so I guess there are subtle
variations.

> The only plan so far is to use some nice "dome nuts" (aka Acorn nuts)
> I found as the contacts.

Neat. I have even heard of people using dinnerware as contacts, and
playing the Kraakdoos by eating a meal! The brass knobs feel great, but
for my next unit I will likely use metal banana jacks, so I can connect
it to other conductive things.

> Since you guys were talking about the PackTec stuff, I took a look at
> their website and it looks like the have some nice items... even some
> designed with 9v batteries in mind.

Indeed, I just happened to find somebody selling two types of cases I
needed on eBay at the same time. My patience finally paid off. I
guessed this case to be for 9v battery, but it's for two AA. Since my
9v clips are bulky I had to grind out a couple pieces of plastic, but
it was easily remedied.

Off to play!


		
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