https://archive.org/details/555-timer-adj-af-generator-schematic Around 5 years ago, I've wanted a dedicated AF Generator as an audio feed for audio amps, my P.O.S. early 70's B&K (Im)Precision RF Generator, (Hi-hi...), and to inject into MIC inputs on transmitters. Now, I have one of those mid-90's Tenma portable AF Generators, utilizing a 555 Timer in it, and uses a 9VDC battery, but I wanted something bench dedicated. So, from leftover parts on-hand, I did up that Adjustable 555 Timer AF Generator. And, to my surprise, it's been, and still remains, my most popular Archive .ORG download. (Interesting...) The circuit pretty straight-forward, a 12VDC, 300mA, rectified and filtered wallwart, leftover DC Barrel Connector jacks, a switch, filter CAP. Now, why did I use an oddball LM7810 +10VDC, 1A, voltage regulator? I have a bag of these on hand that I believe I had given to me by the engineer of Houghton College's, then, WJSY. (The price was right. And, I've used these in several projects.) The rest of the circuitry I've either cobbed from the 555 Timer Cookbook, one of those various TAB Books here, or even from my college text books. Where ever I got the circuit from, it works. BTW, this produces a Square Wave, so to get a nice, clean, Sine Wave, an RC Filter was built for that. It's tuned best for 1kHz, but still filters for the other FREQ ranges. I have in the TEXT Notes what the range is. Yes, that RC Filter does attenuate. However, if you want more audio beefiness, a headphone amp, computer speaker amp, etc., can be added to do so. But, for most of my bench purposes, I don't really need one. Oh yeah, I know there are APP out there for your smart phone and tablet for a free AF Generator APP. And, they work... Whatever you want to use this circuit for, learn, use, enjoy. BTW, while you are on Archive, check-out the rest of the page.
https://archive.org/details/@thadood
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