Digital Data Transmission

Dear Senior,

I would like to get help in Digital data transmission. Because recently i have implement my laser music transmission in ANALOG signal. so i would like to improve the signal-to-noise ratio where i was thinking to convert Analog signal to Digital.
However, i thought it will be easy by connecting the analog signal to ADC(analog-to-digital converter). But after i go through the ADC, i found that is not so easy. or i m not really understand bout that.

so i would like to request seniors to get some idea or any i need to take care on this issue. To convert the audio signal from analog to digital.

Thank you.

anson.

Ehm ..... sorry, but is not so easy ..... you need to connect a low distortion DAC on a sampling circuit, then sample the output of the DAC extremely quickly (also just for a 128Kb/s sampling rate, imagine the speed), then to a system processing the signals for pack them in bytes, then to a sending circuit ..... and the reverse on the other side, too.

Not for try to discourage you, but it's not matter of hobby mount ..... probably the better solution for you, if you want to do that, is to buy already complete converters ..... if instead you still want to do it in DIY/hobby way, there was some kits available, where all the part of preamp/filters calculation was already done, and the conversion was demanded to specialized DSP IC, like as example this one, but i don't know where or if they are still available, sorry about this.

I dont see why it would not be possible. Obviously you need proper ADC and DACs to get it to work, but the optical part of the whole ordeal might not be so difficult.

I would suggest starting out with a wired version, where you do the ADC, the serialize the data and manchester-encode it. You can run the bitstream by wire to a circuit that does the reverse (recover the carrier, feed the serial data to a DAC and output the sound).

Once you get that to work, rigging it to a laser communications device should not be much harder than building the analog one you currently have. Its probably a matter of gain control and schmitt-triggering on the receiving end.

One major difference is that your electronics will have to be bloody fast to pull of CD quality sound - 1440 mbit uncompressed, resulting in a 2.88 MHz signal after the machester encoding run... and possibly quite a bit more if you need any error correction.

Check out Sam's FAQ on the subject.

For the digital to analog conversion part, i have found this kit in ebay (smd components already soldered, they say), but i'm unable to found the equivalent for analog to digital part ..... perhaps none sell them, on ebay ?

Things like those might be interesting too. You might be able to start out with existing toslink hardware, and replace the optoelectronics with free space devices instead of fibre coupled ones.

I dont have detailed knowledge on how those devices work, but its an interesting option potentially saving you a boatload of work.