Impedence and Level matchine

Discussion in 'The Projects Forum' started by georgelawshe, Aug 15, 2013.

  1. georgelawshe

    Thread Starter New Member

    Mar 17, 2012
    11
    0
    I am trying to build a circuit to feed a cassette recorder headphone output into the microphone input on a laptop.

    Any suggestions?

    George​
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    It depends on the input of the laptop - is it really a microphone input, or is it a line level (more likely)? It might even provide power in expectation of a powered microphone. You really need to know.

    Also, might the cassette be plugged in to the wall at the same time as the laptop? There is some concern when connecting the ground connectors of two power supplies.
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,789
    The safest circuit is 600Ω 1:1 audio transformer followed by an adjustable resistive attenuator and coupled to the laptop microphone input via a 100 uF capacitor.
     
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