Question

I am have a weird problem.  I have helped a local church install a new sound system.  We have installed everything completely new but used their existing electrical system.  Admittedly, we made attempts to isolate ground prior to install but the contractor didn't do an adequate job so we are currently testing with the ground jumped until they get another dedicated ground installed.  Anyway, our problem is with a condenser lectern mic and not being able to get phantom power the 130' to the stage.  We have tried this with another lecturn mic and repeated the same results.  The RM16AI provides phantom power when the mic is plugged in directly to the board, but when we connect into the other end of the snake, we get no power.  We confirmed that the wiring is exactly the same on both ends of the snake and they work fine with un-powered mics.  My understanding is that there shouldn't be any line-loss here.  Any ideas for trouble shooting?

Answer 1

The cable run may be too long and or may be subject to RF interference. For cables that are too long, the cable has a certain inductive capacitance based on the length and thickness of the wire. At some point in the cable the current drops so low that the resistance of the cable stops the current flow. RF interference on a poorly shielded cable can cause signal lost much earlier in the cable length.

To resolve this you can employ an RM Ai mixer in Stage Box Mode that connects directly to your Ai Mixer using a single Gigabit Ethernet cable direct connection. This would show up as the Digitalia inputs on the main Ai console. Learn more about the Rack Mixers here. 

An alternative would be to use Battery Powered Mics on long cable runs. 

Make sure you're using quality connectors on your XLR cables as poorly maintained or constructed connectors can cost you signal lost at each end. Also make sure you're using a quality cable that is properly shielded.