jejt / jmons

Engineering Tommorrow

Audio and the Old Man

Dave and me are trying to build an audio project, which is all about sound manipulation. Dave’s the musician of the two of us, and I know nothing about sound whatsoever. We’ve got a primitive system using a Arduino that will produce sounds out of an R2R Digital to Analog Converter, but we’ve got no real idea about generating the wave form. If only we could sample…

About ten years ago, my dad mentioned in passing a short story… Before I was born, and we’re talking about the mid 70’s here, or maybe even possibly early 70’s. Either way, the styles where much different to now. He was helping a friend of his build an Digital Audio project. Sound familiar? Time to pick the old man’s brains.

Anyways, it turns out, back in the day, they built a device which sampled audio from a microphone by converting its voltage into a number, then saving it to memory, then, synchronized, retrieving the elements from memory and playing them back. Yes yes, it’s an echo box. Primitive but worked. If his memory serves him right (and we’re talking my entire life span here, and he’s had a lot of stress in that time – he’s my Dad after all) he thinks that they only sampled at about 50 times a second. Apparently, even cooler, whilst it was a digital system, they didn’t use any form of micro controller – they did the entire lot in Digital Electronics, making the controlling circuits using just logic chips. Thats hardcore. Anyways, back to the point of this.

Why couldn’t I have worked this out? My mind is stuck in this world of high tech digital quality sampling on one side, and on the other, using really high frequencies which sampling at 50hz seriously won’t cut it but that doesn’t matter does it! Either way, I’m now set to sample data on the analog port, and then shove it out again on the R2R DAC on the other side.

Ok, time for some diagrams about what I’m talking about.

Ok that was the worlds most boring diagram, but it gets the point across I guess. Sorry about the ? with the other side of the microphone. I have no idea what this should plug into, and actually, I have very little idea where I’m going to get one from. I have a suspicion I’ll be plugging it into a computers line out or headphones port into a jack there. For those of you who don’t have a clue what a R2R Dac is, then check out this page and erm, I guess thats it for now until this has actually been built.


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