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audio ADC

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zachtheterrible

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Im not sure what kind of ADC to get.

What I need is something to encode sound and voice digitally, then decode it back so that itll come over a speaker. I need it to be very sensitive, not just geared to voice, but to hear all the sounds that you normally would if you were standing there.

This is going to be used wirelessly, so ill need two seperate ICs: the encoder and decoder. I don't need to store the data or anything like that: its going to be real-time.

What would you suggest? Im making an order from digi-key, so i figured i'd order this while i'm at it.
 
Zach, in my opinion the point of digitizing a sound is to store it , for later playback..
or doing digital filtering on it , for later playback..
or doing an FFT on it for later viewing...
lol there seems to be a theme here...
 
Zach, for your application, there is no need to digitize it.
 
the reason that i need it to be digital is im going to try to send voice over the little RF modules, and most of them won't accept an analog input signal.
 
Since you mention wanting to hear everything, I assume you will not be doing just voice. Thus you need to build a lowpass filter off the microphone to filter out everything below 20KHz and the ADC must have a minimum sample rate of 40KHz which is pretty fast. 8 bit audio quality is not too bad, 16 bit is better.

Note that the faster PIC18 series with a 40MHz clock runs at 10MHz instructions/sec. That is 250 cycles per sample. So what I'm getting at is the code can do it, but it better be efficient. Parallel interface would be nice! You also want to look at the baud rate possible through your wireless system. There doesn't look like enough cycles here to do a FFT at this sample rate unless maybe you get a DSPIC, even then I don't know if it can do it, so compressing the signal seems unlikely.

Reducing your freq response requirements may help you. Ideally you want a chip that does audio range sampling AND compression on chip. I'm sure there are some but I'm not familiar with them.
 
zachtheterrible said:
the reason that i need it to be digital is im going to try to send voice over the little RF modules, and most of them won't accept an analog input signal.

And they won't send the quantities of data required for any sort of audio quality either!.

Assuming no compression (which would be difficult to do, particularly in real time) and only 5KHz bandwidth (low quality), sampling at at least 10KHz would provide 10,000 samples a second. Assuming you're only using 8 bit samples, this would require a 100,000bps radio link.
 
You wod need realy fast radio modules for that!

It wod be much simpler to use an FM radio transmiter whith an preamp and an FM radio on the other side.
 
Oh yea but then evry one cod pick it up whith radios.

meaby is you tweak an mini radio to work a bit outside the comercial FM band and the transmiter too.

You didnt specefy the distance
 
By my saying that i want to hear everything, what i mean is that I just want it to be very nice and clear, not all garbled, and "digital" sounding, like a low data rate.

So what you're saying is that this is basically impossible. I would probably have around a 10k data rate.

I guess I'll just look around for a radio module with an analog input.

Is there any chance that I could hack those things to inject an analog signal? It would be very easy to sit down with one for a half hour and draw up a schematic.
 
Its not imposible but stupid to use digital just for audio transfer

You can get modules that work on 2,6 Ghz these have enugh bandwidth to do this but i think there pricy.

Its way cheaper an smaller to build an simple FM transmiter and use your radio to recive it.There are chematics for comercial band FM transmiters all over the net(there are some on electrotech too)
 
Thats the thing, I don't want to use the FM transmitters that are cheap, unreliable, very little range . . .

I want something that has a stable frequency, and I don't want to use a regular radio. I also don't want to use 2.6GHZ, as range is severely decreased, and higher power levels are needed.

So how hard is it to inject an analog signal into one of those RF modules? I'm sure it would be especially easy with an AM one.
 
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