Electronic Circuits and Projects Forum



digital voice recorder

  1. #1
    piyush_it1 piyush_it1 is offline

    digital voice recorder

    my project includes sampling the voice using ADC and storing the data in flash memory and finally retreiving it from memory using DAC. The platform being 89c51 microcontroller

    1.) i've made a basic preamplifier and checked it's o/p on CRO and it's amplitude is limited to 1V. I want to know whether my ADC could sample such variations.

    2.) Please tell me some power amplifier configuration
    (if possibly LM 386)to test the o/p of this circuit , by connecting it at o/p of this circuit,without connecting it to microcontroller.


    thanks

  2. Thread Starter #2
    piyush_it1 piyush_it1 is offline

    schematic

    my circuit is not attached as attachment. Kindly help.[/img]
    0

  3. #3
    akg akg is offline

    Re: digital voice recorder

    Quote Originally Posted by piyush_it1
    1.) i've made a basic preamplifier and checked it's o/p on CRO and it's amplitude is limited to 1V. I want to know whether my ADC could sample such variations.
    most of the ADC i/p varies from 0-5V for FSD , so u have to amplify the signal 5 times to get the full resolution of the adc.

    2.) Please tell me some power amplifier configuration
    (if possibly LM 386)to test the o/p of this circuit , by connecting it at o/p of this circuit,without connecting it to microcontroller.
    u can find sample design of poweramp in the datasheet of lm386
    0

  4. #4
    Nigel Goodwin Nigel Goodwin is offline
    Super Moderator
    A couple of points for digitising audio:

    1) You MUST have a low pass filter on the input, with a fairly sharp cutoff no higher than half the sampling rate, and preferably lower than than.

    2) You MUST make 100% sure that you NEVER clip the input to the DAC, this produces incredibly bad distortion
    0
    PIC programmer software, and PIC Tutorials at:
    http://www.winpicprog.co.uk

  5. #5
    akg akg is offline
    Quote Originally Posted by Nigel Goodwin
    A couple of points for digitising audio:

    1) You MUST have a low pass filter on the input, with a fairly sharp cutoff no higher than half the sampling rate, and preferably lower than than.

    2) You MUST make 100% sure that you NEVER clip the input to the DAC, this produces incredibly bad distortion
    ADC ??
    0

  6. #6
    Nigel Goodwin Nigel Goodwin is offline
    Super Moderator
    Quote Originally Posted by akg
    Quote Originally Posted by Nigel Goodwin
    A couple of points for digitising audio:

    1) You MUST have a low pass filter on the input, with a fairly sharp cutoff no higher than half the sampling rate, and preferably lower than than.

    2) You MUST make 100% sure that you NEVER clip the input to the DAC, this produces incredibly bad distortion
    ADC ??
    Yes! - sorry ops:
    0
    PIC programmer software, and PIC Tutorials at:
    http://www.winpicprog.co.uk

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Electronic Circuits  |  Learning Electronics

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