DAC0832 with LM386 and LM324

Discussion in 'Homework Help' started by zhane, Apr 4, 2008.

  1. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
    is there any circuit diagram out there that I can use to interface the above to a 8ohm speaker and 80188?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    There are data sheets for all three devices readily available. The data sheets describe how to connect and use them. I think you're going to need to add a PIA to the 80188 for the interface.

    These are very old components, so this must be a school assignment.

    I'm not familiar with the 80188, but it should need an interface chip. That would be the PIA (parallel interface adapter). It sends data through that to the D to A converter. Using a low pass filter, the output of the converter goes to the 324 (or part of it - it's a quad op amp) and then the buffered and amplified analog signal drives the 386, which has enough poop to drive a speaker.

    Read up on everything and come back if you have some specific questions.
     
  3. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
    im able to produce sound right now, but there is alot of noise that comes with it
    how should i remove the noise?
    DAC> LM324> LM386
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Try a passive filter between the DAC and the amp. A cap & resistor in series to ground across the amp input might shunt out the sharp transitions from the DAC.
     
  5. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
    what kind of values should the series capacitor and resistor bE?

    i just added decoupling cap of 0.1uF to both of my LM324 and LM386, nothing improves
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You need a low pass filter between the output of the DAC and the input of the op amp. The DAC output switches from one state to the next very rapidly, which is where the noise is coming from. The filter will smooth out the rapid transitions and make the sound quality more acceptable. Most audio DAC's are 16 bit, so your audio is never going to sound really good.
     
  7. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
    what kind of cut off frequency should we set it at?
    my sound is recorded at 8kHz

    and..the output from DAC is current, it's safe to pass it thru e filter just like that?
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Resistors are current to voltage converters. Put the corner at a bit above 8 KHz so you don't roll off your high frequency response too much.
     
  9. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
    u refering to the resistor in the lowpass filter?
    or another additional one?

    so i just need to get

    Iout > Lowpass > LM324 > LM386?
     
  10. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
  11. zhane

    Thread Starter New Member

    Apr 4, 2008
    7
    0
    ive changed my circuit to
    [​IMG]

    there is still this buzz sound which i cannot remove

    it sounds like this

    is there anything else i can do?
     
Loading...