Phantom Power Not Transmitting Through Walls

  • Thread starter Thread starter BrianAltman
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BrianAltman

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Hey All,
First time poster here. I recently built a studio and I'm encountering a very strange issue in my house channels. After some testing I have identified that audio does not transmit when phantom power is enabled and trasmitted through my house XLR outlets, as seen in the test scenarios below:

Scenario 1: audio transmits correctly.
Any Condenser Microphone > XLR cable > Audio Interface (phantom enabled)

Scenario 2: audio transmits correctly.
Any Dynamic Microphone > XLR cable > XLR Wall Outlet > Control Room Output Snake > Patch Bay > TRS Patch Cable > Audio Interface (phantom disabled)

Scenario 3: No audio is transmitted.
Any Condenser Microphone > XLR cable > XLR Wall Outlet > Control Room Output Snake > Patch Bay > TRS Patch Cable > Audio Interface (phantom enabled)

Scenario 4: audio transmits correctly.
Any Condenser Microphone > XLR cable > Any analog mixer (phantom enabled) > XLR cable > XLR Wall Outlet > Control Room Output Snake > Patch Bay > TRS Patch Cable > Audio Interface (phantom disabled)

All microphones, cables, and interfaces have been throroughly tested and are in working order. When phantom power is not transmitted through the walls, but instead applied in the same room, sound is present. When phantom is not required, sound is present. Sound is only not present when phantom is enabled and transmitted through the walls.

My gut says there is some sort of external power interference, but I dont even know where to start looking. I have a total of 52 channels and this issue exists on every channel.

Does anyone have any ideas on where to start troubleshooting this issue?
 
Using your DMM, can you measure 48 volts between pin 1 and both pins 2 and 3 on your wall outlet?
 
This transmitting through walls, you mean have an XLR female in one room and the other end with the male plug is in the other room - the audio path goes via a patch bay.

While it does work, patchbays are NOT normal for phantom power, because once they start to tarnish, you get crackles, pops and eventually deadness.

My thoughts are that somewhere in the journey you have a short between pin 1 and pin 2, or pin 1 and pin 3 - this will prevent a phantom mic powering up. A dynamic mic would work fine with this short.

All your working scenarios that you've listed would not object to the short - so the best thing to do is to get your meter out and test that pin 1 of the send connector arrives at pin 1 the other end, and does not go to pin 2 or 3. Easiest way would be a long XLR to get the other end back near the other connector then do the test between 1 and 1, 2 and 2 and then 3 and 3 checking for no shorts. We tend to use the word 'send' not transmit - as that gets confusing when we have radio mics!
 
Right, test for shorts as well as continuity and voltage present.
 
Brian,
By any chance is the Control Room through wall snake an ethernet type cable?
I recently added more cable connections to my drum booth via ethernet / CAT 6 type cabling and had the same exact problem.
Later found out the standard CAT cable I used through the walls was not shielded type CAT cable so there was no proper path for the Phantom power.
Changing the CAT cabling to fully Shielded gave me Phantom Power.
 
"Scenario 3: No audio is transmitted.
Any Condenser Microphone > XLR cable > XLR Wall Outlet > Control Room Output Snake > Patch Bay > TRS Patch Cable > Audio Interface (phantom enabled)"

If you are plugging a TRS cable into the audio interface, phantom is not put onto the TRS connection of the interface, only the XLR connector, thus no phantom will get to the mic.
 
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