Choosing the right transistor

DIY STUFF
1

I made this simple noise circuit for drum sounds:

noise
noise2719×1974 282 KB

On my testing bench, I use +/-15V supply (because I don’t have +/-12V supply).
I tried with 2N2222A, and everything was fine, my drum module was working well!

So I moved it into my case, where I have a +/-12V supply. And (“Oh surprise!”), no sound out of the module! A bit puzzled, I went back to my bench, made a sketchy contraption to power my module in a more controlled manner, and decreased the input voltage gradually, while monitoring the noise output.
15V: Good
14V: A bit less, but still good
13V: A bit less
12V: Nothing at all, D’oh!

Well, crap.

I then tried with S9013 transistors. And it worked down to ~9V!

So yeah I thought it could be a good resource to have here, if you have other examples where not-all-transistors-works-but-I-don’t-really-now-why. (I know there is a lot of issues with the SSO for example, but this one already have a full thread)

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2

Did you try varying the resistors too? I haven’t experimented with that topology but with this

NC00

the value of R2 is significant in whether it makes noise or not.

3

Yep, forgot to mention, but that’s the first thing I tried, with no result. My explanation is that 12V is less than the zener/breakdown/avalanche voltage of the transistor, so it can’t produce shot noise.

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4

that"s a good question.
Sam answered this I think in a follow-up video about the super simple oscillator.
also check this page that Sam mentioned about this :slight_smile:
http://www.kerrywong.com/2014/03/19/bjt-in-reverse-avalanche-mode/
Hope it helps… I’m using SS9018 in my oscillators.

All the best

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