3 amplifiers inputs connected in parallel

Discussion in 'Archived Threads 2001-2004' started by John H, Jul 30, 2002.

  1. John H

    John H Second Unit

    Nov 27, 1998
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    I am putting together a dedicated headphone system. It will have 1 SS and 2 tube headphone amplifiers.

    What load will these 3 amps connected in parallel present to my source player?

    Imput Impedance

    1. 55K
    2. 100K
    3. 100K

    Final load 26K?

    Will the load change if any combination of the 3 amps are not powered on? My player specifies a load of >10K.

    Would a parallel configuration be acceptable or should I install a line switcher?

  2. Mark Tranchant

    Mark Tranchant Stunt Coordinator

    May 9, 2002
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    Yes, 26Kohm - assuming the input impedance is constant with frequency on all three amplifiers.

    The combined input impedance with amps powered off depends on the circuitry used. Simple op-amp input stages would not change significantly when powered off, and I wouldn't expect any circuitry to reduce its input impedance when off.

    You should be OK, but watch out for grounding differences bewteen the amps. Properly-deisgned stuff should be OK, but cheap stuff may have significant "signal ground" voltage differences, which you'll be connecting together.

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