Coupling Audio Stages Together

Discussion in 'The Projects Forum' started by irobot2020, Jun 5, 2016.

  1. irobot2020

    Thread Starter New Member

    Jun 1, 2016
    6
    0
    I have two audio stages to connect.

    The circuits are taken from the datasheets of the IC's. Would you use both capacitors C8-C6 (right channel) and C9-C7 (left channel) in series or just one cap? If just one cap, what value? Any resistors needed? Side note: The output impedance of the SI4735 chip is about 20K, the input to the TDA7052 is 10K.
    interface.PNG

    Side note: The output impedance of the SI4735 chip is about 20K, the input to the TDA7052 is 10K.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    According to the datasheet, you can connect it without a problem.
    The minimum load is 10K.

    I have attached the datasheet and an evaluation sheet.

    Bertus
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,949
    385
    You will only need one capacitor for each channel BUT you should watch the dc level of the outputs and inputs if using polarised capacitors. The TDA7052 shows 0.47u capacitors and they can easily be a non-polarised type which avoids the DC problem.
     
  4. irobot2020

    Thread Starter New Member

    Jun 1, 2016
    6
    0
    Thanks Albert

    Question is, do I use a 4.7uf or .47uf to couple these stages? I have run into this issue many times before when connecting various audio circuits together.
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,949
    385
  6. dannyf

    Well-Known Member

    Sep 13, 2015
    1,810
    362
    That's quite rare.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    Danny is right. The input impedance is typicaly 100 kΩ.

    TDA7052_characteristics_input_impedance.jpg

    Bertus
     
  8. crutschow

    Expert

    Mar 14, 2008
    13,013
    3,233
    Note that the input bias current (Ibias) is up to 300nA so you need a resistor to ground to provide that.
    The application diagram shows 5k:
    upload_2016-6-5_7-51-4.png
    The coupling capacitor should then be ≥4μF (4.7μF is fine) to get a 20Hz rolloff.
     
  9. irobot2020

    Thread Starter New Member

    Jun 1, 2016
    6
    0
    Thanks for the replies . . . my bad, I meant to type 100K input impedance for the amp stage . . . .
     
  10. irobot2020

    Thread Starter New Member

    Jun 1, 2016
    6
    0
    So am I correct in saying that the 5K R(s) is also effectively changing the input impedance to around 5K, or maybe a little less?
     
  11. crutschow

    Expert

    Mar 14, 2008
    13,013
    3,233
    That is correct.
    The 5k is effectively in parallel with the 100k input impedance for an equivalent input resistance of about 4.76k.
     
    irobot2020 likes this.
Loading...