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We have an organ at front of house that we're hooking up to our sound system. The organ has a balanced 1/4" output that we're planning to use and send to our mixer over XLR. We were considering sending the organ output through a direct box to protect the organ in case phantom power was accidentally turned on for that channel. However, since direct boxes are normally for unbalanced inputs, I'm concerned running a balanced connection to the direct box could short the connection or otherwise defeat the purpose of the balanced connection. (We seemed to be getting dropouts and other weird issues using an unbalanced 1/4" cable, hence the need to stick with a balanced TRS cable and make sure the entire flow supports balanced signals.)

So, how best to address our two concerns/requirements without over-complicating things?

  1. Prevent phantom power from reaching the organ.
  2. Keep the entire run compatible with balanced signals (so that at no point in the flow the inverted signal is simply ignored, as I'm afraid could happen with a direct box).

I'm fairly new to this area, so forgive me if I'm not explaining things 100% correctly.

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  • Does the mixer not have any balanced 1/4” TRS inputs? If you want to use an XLR channel on a snake just buy adapters for both ends. In terms of DI with an unbalanced cable, it shouldn’t cause any problems. If it does, it’s more likely a bad cable than anything related to using an unbalanced cable from the organ to the DI
    – Todd Wilcox
    May 2 at 12:13
  • @ToddWilcox We're using a Yamaha MG12XU mixer. I believe the manual was vague when I checked, but inputs 1-4 support balanced inputs for XLR, and therefore I'm guessing balanced on 1/4" as well (though not 100% sure). I'm also unsure if the mixer would send phantom power through the 1/4" jacks -- I would assume only XLR, but again, not sure.
    – thatWiseGuy
    May 2 at 13:09
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    No major company like Yamaha will send phantom power on 1/4”. It would be a disaster for so many reasons.
    – Todd Wilcox
    May 2 at 22:21

2 Answers 2

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With the Yamaha MG12XU, you'd either use the balanced line inputs on the XLR/TRS combo sockets of channel 1 to 4 with a suitable balanced TRS cable (TRS sockets never carry phantom power as a rule), or you'd use one of the unbalanced line inputs (channel 5 to 10) with a TS cable and a passive DI put in reverse (XLR cable from the organ into the XLR "outputs" of the DI, likely requiring a gender changer, connecting the DI "inputs" to the unbalanced line inputs of the mixer).

Note that passive DI boxes can be used in reverse as long as you don't engage any optional attenuation.

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If the only thing you need to be sure of is that phantom is not going to ever go up that cable, then Triton audio make the Phantom Blocker which does that & only that.

As I have no clue how strong your signal is going to be on such as an organ, then you might also need a pad, for which they also make the AirHead attenuator, or a boost… for which they make a whole slew of preamps - https://www.tritonaudio.com/products - some of which pass phantom & some of which don't.

No affiliation to the company - I just have a soft spot for guys who build esoteric one-trick ponies & don't charge the earth for them ;)

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    Good suggestion about the Phantom Blocker. I see it has a strict startup sequence of applying Phantom power for a few seconds before connecting the instrument/device. My only concern is that we won't be able to run through this sequence on each startup--and the organist may already be practicing when we need to power on the mixer/phantom power. The blocker would need to stay connected long-term, without being able to guarantee the startup sequence. Given the unknowns, I'm hoping to run TRS into our mixer to avoid the issue altogether, after thinking about it more.
    – thatWiseGuy
    May 14 at 0:08

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