Power for MRA Amps

Discussion in 'Multi-Room Audio (MRA) and MARPA' started by znelbok, Feb 11, 2018.

  1. znelbok

    znelbok

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    When using a MRA amp in standalone mode you need to use a 24VDC power supply - the larger amp (24W) needs a 4 pin mini din plug which is painful as its not an off the shelf option for power supplies.

    When using the amps with the matrix switch you don't need a power supply - so that would mean that we can power the amps up via the digital Audio connection (RJ45) on the back - a sort of POE type setup.

    What are the specs for power on this connections and would it be feasible to power up the amps via the RJ45 plug when in stand alone mode? It may be simpler than trying to get a min din plug and guess the polarity
     
    znelbok, Feb 11, 2018
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  2. znelbok

    NickD Moderator

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    The power on the mini DIN is on pins 5/8* and 3/6 and is polarity independent (there is a bridge inside).

    The power on the RJ45 is - on pin 1 and + on pin 2.

    I don't have the specs on the voltage/current for the PS at hand but from memory it's 24V.

    Nick

    *ie pins 5 and 8 are internally connected, as are pins 3 and 6
     
    NickD, Feb 11, 2018
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  3. znelbok

    znelbok

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    Thanks Nick

    The pins are polarity sensitive - I got it wrong once and while the amp powers up fine, the C-bus network side does not work at all - had all sorts of issues on the network. Swapped it around and it was fine. Even the sticker indicates which is positive and negative.

    yes, the Din is 24VDC, but was not sure if the RJ45 was higher to reduce current on the smaller cable (like PoE voltage, 48-52VDC).

    If it was PoE voltages then that would be significantly easier to wire up.

    Mick
     
    znelbok, Feb 12, 2018
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  4. znelbok

    NickD Moderator

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    Nope.. the RJ45 just gets the 24V out from the matrix switcher, nothing clever.

    No idea why the polarity should be important.... the only thing I can think is that since the shield is connected internally to the circuit common (the -ve side out of the bridge), if that were connected to something it shouldn't have been then it could cause problems.

    Nick
     
    NickD, Feb 13, 2018
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  5. znelbok

    Matthew

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    Hi Mick
    The MRA product preceedes PoE.
    I have 2 MRA amps connected to an Audio Distribution Unit, (No Matrix switcher).
    I have one of the 24VDC power supplies plugged into one amp, the other amp gets the power through the interconnecting RJ45, as does the Audio Distribution Unit.
     
    Matthew, Feb 25, 2018
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