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  1. #1

    Mixer to Amplifier

    For a drama production I am wishing to connect more microphones than the permanent sound system has inputs. I have access to a separate sound mixer and wish to know how to connect this to an 'Inter-M PAM-120' amplifier.

    Can I use one of the amplifiers XLR inputs?

    The difficulty that I have is that the amplifier is locked in a cabinet with no access to the rear connectors. However, I do have access to the XLR inputs because these are used generally for microphones, which are disconnected when not in use.

    Am I okay to connect the mixer using an XLR input without damaging either piece of equipment? I am worried about phantom power, balanced/unbalanced inputs etc.!

  2. #2
    If your mixer has mic-level outputs, using those should be fine.

    Just be sure to keep the levels "down and out" (all the way to -infinity) when you connect the mixer if you lack access to the power switch (and keep them down and out with the amp off if you do have access to the power switch) then slowly bring the levels up while feeding tone or a well-leveled piece of music through the mixer.
    Eric Adler (tonsofpcs) Chat at:
    Follow me on twitter: @videosupport @eric_adler

  3. #3


    Thanks tonsofpcs.

    I have not yet seen the mixer that I am due to be borrowing so do not know what outputs it has (xlr or jack), nor whether any are mic-level. The mixer is normally connected to a different amplifier, but the idea is to disconnect it and connect to our equipment.

    My main concern is not damaging any equipment as this could be expensive. Is there no risk of any 'phantom' power being sent down the XLR cable and into the mixer (I have no access to turn of phantom power in the system!)

    One more question: Looking at instruction manuals for various mixers on the internet, they appear to have separate xlr outputs for left and right. How do I connect a mixer such as this to a single xlr input, normally used for a microphone?

    Thank you for your time and knowledge!

  4. #4
    Put one into one, one into the other, use the controls to pan them hard left and hard right in the amp. If the amp lacks pans, just plug one of them (lets use left) in and pan everything to that channel (left) with the mixer.
    Eric Adler (tonsofpcs) Chat at:
    Follow me on twitter: @videosupport @eric_adler

  5. #5
    Actually, I hate to tell you this, but you could damage the mixer. If the mic inputs have phantom power on them, it could be as high as 48 volts. Many mixers have electrolytic capacitors in their outputs and this would reverse bias them, leading to their destruction.

    When a mixer has a mic output, it's usually just the line output attenuated by an internal pad. Occasionally a mixer's mic output will be fed by a transformer - then you're safe. But if it's just a pad, you could be in for trouble.

    Is it possible anywhere in your area to buy a high-imedance unbalanced to low-impedance balanced inline transformer? If you feed the mixer output into the high impedance end of the transformer (at fairly low level, they're easy to overload on low frequencies) and plug the low impedance output into the mic jack, you shouldn't have phantom power troubles.

    Here's an amusing/aggravating factoid to keep in your knowledge base: some manufacturers of wireless microphones have receivers that cannot be used with a phantom powered input. How boneheaded is that?

  6. #6
    Thanks Karl and tonsofpcs

    That was my concern (about blowing up someone elses mixer!!!), although I don't understand all the terminology that you used.

    I am in no position to buy anything, as I am not the owner of either piece of equipment.

    Are you suggesting that if I requested access to the rear of the amplifier and turned off phantom power (for the mic input that I was using) then I would be safe to connect the mixer?

    Or how do I tell what kind of mic output the mixer has? If possible I don't want to change any settings on the system.

    Thanks tonsofpcs for the advice about connecting left and right. I will have to connect just the left and pan left on the mixer. Unfortunatley the mic sockets are not located alongside each other and are distributed around the room, so I cannot connect left and right separatley! I expected that I would just have to connect the left.

  7. #7
    If you can get into the rack and turn off the phantom power, you would be safe. Otherwise... maybe the group you're doing this for would spring for the inline transformer? I haven't checked recently, but I think they're well under $50.

    You are sure you have phantom power on those mic inputs, aren't you? A voltmeter between pins 1 and 2 will tell you.

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