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Old 07-10-2021, 12:52 PM   #53
clearchris
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Default Re: Signal Tracer - Requesting input on requirements

Quote:
Originally Posted by eccerr0r View Post
I have a 2sc458 that I coupled with a LM741 specifically to make white noise
Just need a power source and hook up an amplifier to it...and it's pure hiss...
Yeah, this chip would have worked great, except then it picks up AC hum too, probably adding too much non-randomness to it. Last I heard of this (and it has been a long time) people were cracking open smoke detectors, taking out the radioactive bit and attaching it to a sensor...

Quote:
Originally Posted by redwire View Post
Glad you found it, crypto guys need pure white noise for random number generation, that bad IC could be worth a fortune lol.

The 1.35k resistor is built into the IC (across pins 1-8) to set its gain at 20.
A lower impedance between pins 1-8 increases the gain. Max gain 200 is with a 10uF cap and no resistor there. Gain of about 52 (34dB) is with a 10uF and 680R for example.

You could have a high/low gain switch that just puts in the 10uF+resistor or not.
The input pot lowers gain, the amplifier should be quiet with the pot set low and no long input cables.
Yeah, no kidding. Super loud, only reason I didn't suspect it sooner is that everyone online seems to complain about hiss and noise with this chip and people respond to ground the chip better. But yeah, after attaching everything to the back, and it not making the slightest bit of difference...

A switch isn't a bad idea, I might even have something suitable on hand instead of trying to get a 2k reverse audio taper pot. Initial testing shows that having longer leads on the 1 and 8 pins doesn't affect the sound much if at all.

I have been playing some songs through this setup so I can compare when I add the longer shielded leads, and I'm now pretty impressed with this setup, it sounds far better than my logitech computer speakers. I did buy a supposedly decent speaker, IIRC, I spent under $15 for a pair, but you never know what you are going to get when you import electronics...

BTW, does anyone have any opinions on which side (or both) of the shield from the shielded wires should be grounded?

Last edited by clearchris; 07-10-2021 at 01:14 PM..
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