Kinks White Noise Generator

Hello :slight_smile:

I’m trying to understand how the kinks noise generator works. I would love to build a DIY Geodesics Branes, so I’m very interested how to generate noise.

First. I’m not an expert. I’m just willing to learn things. I do some calculations of the Q Point of Q2 and tried to calculate the noisy ac output voltage, but I’m not sure if this is right, cause I never worked with noise before in such a way.

Then I build a test circuit with some BC547B (I don’t have some MMBT3904 here), but the test was a big fail. I did not understand why I could measure a V_BEO Voltage of 10 Volts or more. Shouldn’t the transistor Q1 work in breakdown? (for the BC547B V_BEO = 6V, too I think). And my DC voltage at V_out was almost Vcc (12V).

I didn’t understand anything. Is this only because the choice of another transistor? (I thought they have similar characteristics) Is my calculation false? I don’t get it.

I already asked some of my fellow students to help and get some interessant answers: They mean I should use a Emittier Resistor with a bypass cap to stabilise the Q Point, but in the Kinks module its working without one…

So I would be very helpful for any kind of help :smiley:

THX and double THX
Gruftgrabbler

EDIT: I forgot to check my assumption that Q2 is working in saturation mode:

V_CE2 > V_CE,SAT = 0,2V
1,4V > 0,2V so the assumption was correct

I’m afraid I can’t help you with this, this was designed with the very helpful technique of “trial and error”.

5 Likes

Haha I like your approach, maybe I will try this, too :stuck_out_tongue: And maybe I will hear to my fellow students and add some q point stabilisation :slight_smile:

It’s been ages since I dabbled in electronics but I came across a similar schematic that may provide some answers:
https://www.eeweb.com/extreme-circuits/simple-white-noise-generator

2 Likes

I would be happy to try to understand what you did there, but unfortunately, that circuit diagram means almost nothing to me.

Could you draw it out with conventional component symbols? No promises, but I’d stand a much better chance of undestanding that. I’m guessing what you’ve drawn is what you expect to be happening, in terms of current sources? That really doesn’t help, without seeing the actual circuit.

Alternatively, yes, just google for existing, well documented, noise circuits - e.g for the ARP Odyssey, or the Minimoog.