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Old 2011-09-29, 05:25
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Dystopia Dystopia is offline
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Electronics Project

I'm making a recording-mixer device for my final project of my two year degree. The basic idea is that I plug in my Simmons E-drum module (all inputs are 1/4" TRS), press a "RECORD" button (which may trigger a timed delay before recording), play drums for 5 minutes (hopefully for a prototype, at least!!), THEN, after pressing stop and plugging in the bass for another track, press the button again to record with any previous track recorded to play at the output to allow simultaneous record/listening. Then, repeat with rhythm guitar/lead guitar 1.

THEN, the ultimate goal is to press PLAY and pluck the strings of my guitar while an invisible band is playing behind me. The algorithm is this:

EMI input >> ADC >> MEM >> DAC >> Output: Amplifiers

EMI = Electronic Musical Instrument
ADC, DAC = Analog to digital, digital to analog, Converter
MEM = Memory

Basically I need to know a couple of things to get the ball rollin', and I need professional help as I don't want to risk damaging anything plus this has been hard as shit to google... Only one of teachers has reliable advice, but he's popular...

1) I need to know the expected output frequency... and yes, I have looked at tables (E=84.5Hz, A=110Hz), but anything you guys can tell me that will help me recreate the input signal to the output signal that is recorded. I know that the sampling frequency must be double the frequency I wish to output to human ears, but that doesn't mean that a 110 Hz sine wave should be sampled at 220 Hz, that would sound too robotic.

2) So that I can accomplish 1, how do I properly measure the signal of my guitar on an OSCILLOSCOPE?
I know that the coils of the magnetic pick-ups convert the energy of the vibrating strings into an intelligence signal to be carried over to amp, but 1/4"TRS (tip, ring, sleeve).. I look at them, and wonder: Where does the power come from? I don't think I can just plug in a cord, measure the other end of it, play some notes and see the wave-form I want.

I've asked my teachers about step 2 and I am told I need to measure it coming from the Amp, which leaves me wondering how does the signal get all the way to the amp without any power pressing it? I mean I'm pretty sure it's (Ring=Right input/ Tip=Left input/ Sleeve=ground). IS THERE power connected to it? Guitar battery?

Before I can determine the ADC that I will need, as well as memory, I'm going to have to get this. After 2 years of computer electronic engineering, I should get this, but there is no guitar-electronic engineering processes, so yeah big step for me. 8 weeks until the presentation! That's my lack of planning; NOT your emergency, but if you could give me the help I may need before someone else does, or until I eventually figure it out somehow, then much appreciated. Typing this thread helped me reprocess it in my head a little, so I at least got something out of it.
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