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RIAA preamp help

Discussion in 'Misc Electronics' started by Daniele - Skrauso, Jul 18, 2004.

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  1. Hi all,
    I found this simple circuit http://sound.westhost.com/p06-fig2.gif to
    preamplifly a phono source.
    Do you think it's good? I don't need extreme quality.. just a well-working
    device :)

    Thanx
    Daniele
     
  2. Jim Thompson

    Jim Thompson Guest

  3. Check it against.... thanx man..
    I noticed that riaa curve cuts heavily high frequences.. I tried a quick
    simulation (generic opamp) with pspice and I got a flat response on high
    frequences!
    So I think I'll have to build another circuit..

    Thanx
    Daniele
     
  4. Fred Bartoli

    Fred Bartoli Guest

    Why ? It shouldn't : there's the 820R/82n time constant at the output.
    You must have made a mistake in your sim.

    When doing this circuit, just think to change the 10u and 22u caps from the
    minus inputs to the ground side (less parasitics).

    Thanks,
    Fred.
     
  5. Why ? It shouldn't : there's the 820R/82n time constant at the output.
    you're right..!
    what do you mean for change? you mean the value or the capacitor type, ie no
    electrolytic?

    Thanx
    Daniele
     
  6. Fred Bartoli

    Fred Bartoli Guest

    No, just exchange the grounded resistor of the feedback network and the cap.
    i.e. :


    minus input ------- resistor ----- cap ----GND

    instead of

    minus input ------- cap ----- resistor ----GND


    The minus input of opamps is sensitive to capacitive parasitics to ground
    (this adds one pole with the feedback resistors) and it's good practice to
    reduce this parasitics as much as possible. Otherwise, from the circuit POV,
    there's no difference.


    Thanks,
    Fred.
     
  7. No, just exchange the grounded resistor of the feedback network and the
    cap.
    thanx a lot.
    I also found the error in the simulation and now it's all working :)

    Bye
    Daniele
     
  8. "Fred Bartoli"
    What do you mean by 'think'?

    The input and output capacitors are missing their plus sign, assuming
    they're electrolytics. The positive on both is towards the 5532.
     
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