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6300: Mic input circuit, actual impedance?

Jim  KJ3P
Jim KJ3P Member ✭✭✭
edited April 2020 in FLEX-6000 Signature Series

When interfacing a mic that has an internal transformer for its (250 ohm) output, it's important to know the actual impedance that the transformer will "see" to assure that the transformer is properly terminated.  Anybody know what actual input impedance is presented by the 6300's mic pre-amp?

Another way of posing this question is:  what kind of load does the radio present to the mic? The specs say:  Microphone Impedance:  600 Ohms Nominal (200-10kΩ). This suggests that the input impedance is high, otherwise a 10K mic might be loaded down too much, but it's just a guess.


  • Paul Christensen, W9AC
    Paul Christensen, W9AC Member ✭✭
    edited June 2019

    A quick check of the schematic diagram would provide the information we need.  Are schematics of the Flex 6000 series available?  I'm interested not just for this reason but to better understand the internal relationships of the Flex 6K hardware.

    Paul, W9AC   

  • Gerald-K5SDR
    Gerald-K5SDR FlexRadio Employee ✭✭
    edited April 2019
    The microphone inputs are high impedance.  The actual impedance varies by the gain setting of the DVGA in the CODEC.  The minimum impedance at maximum gain is about 5k on the front panel mic and about 3k on the balanced input.  The maximum impedance is over 80k at minimum gain settings.  
  • W5XZ - dan
    W5XZ - dan Member ✭✭
    edited December 2016
    me too!  w5xz, dan

  • Jim  KJ3P
    Jim KJ3P Member ✭✭✭
    edited April 2020
    Just what I needed...thanks!

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