View single post by Slider2732
 Posted: Mar 9th, 2008 05:48 PM
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Slider2732

 

Joined: Mar 3rd, 2008
Location: Muskogee, Oklahoma USA
Posts: 349
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Thanks Jeff for that marvellous summary of the component parts :biggrin:

I've built an R2R ladder in the past and have some familiarity with signal processing, but I guess i'm one of those chaps that likes to see what's going on lol
In audio, once things go digital they are lost to me, til they become analog again!
The trickery pokery of the process is what caused the thoughts.

Nevertheless, recent forays have included the binary or hexadecimal realms and resulted in many fun observations. By that, I mean that, essentially, a pin on a chip is usually a 1 or 0, on or off...and then there are thresholds for the switching between.
Some random messing around, that then turned more serious and logical, resulted in my EMF meter based on an Intel 8255. Damn thing works wonderfully, for a 1970's basic I/O chip, with a useful range of about 6ft when a couple of components and a coil were added. It's best for static though, walking past makes the LED's flash lol

So, that lead me to experiments the last few days with a 16pin Toshiba TA7613AP AM/FM audio chip. It was housed in a cheapo portable radio and I wanted to find out what was being output from the thing. Pins 3 and 6 introduce noise to the signal, when a speaker is connected to Ground and either pin. I forget which did what, but a 10uF capacitor on one of them introduced a mild spaciality to the signal. In my opinion, that sounded better than the original signal with AM.

Other experiments over the last few days have been with a Panasonic RN-305 micro cassette recorder. I decided to use this for live EVP. Cut the motor wires, take the cassette mechanism off and hardwire the record and play connections. Finally, the audio out is from the record head area. This results in a 'what you hear is what youd get' type of thing, bypassing the cassette bit altogether. Essentially, whatever goes into the unit while recording, goes straight out of the speaker.
That recorder has a 20 pin chip with no i.d on it. One effect has been with pin 9 on that, an LED to Ground and that pin produces some kind of bounce. The LED reacts like a rubber ball dropped from a few feet.
The other comical thing with the cassette recorder was when I fitted a light sensor from an old mouse instead of the microphone. Can play the thing like a theramin :biggrin:

The way signals are fed around audio circuit chips is now my next area of exploration.
Points at which the signals change is a focus. A datasheet only gives so much information...actually getting in there and altering things may produce clues to minimise our spirit friends problems with communication.


Last edited on Mar 9th, 2008 05:54 PM by Slider2732