I have the following configuration:
TBP12 relay transmitter hooked up to...
Shure WA310 adapter cable from F-XLR to TA4F hooked up to...
Countryman Isomax II BPM Battery powered phantom power supply hooked up to....
Earthworks M23 condenser microphone very flat to 25 KHz.
XD-V70 receiver is hooked up to one channel of a dual channel FFT. Another identical microphone wired directly to the other channel of the dual channel FFT.
Comparing the direct output of the mic vs the output of the above wireless in the above setup, I see a polarity reversal and a HF shelf starting at about 1000 Hz, cutting to about -6dB by the time you get to 10KHz.
Ok, so a process of elimination to figure out the problem:
1. Eliminate the microphones and the phantom power supply out of the equation: a pink noise generator is plugged directly into the WA310/TBP12 and the XD-V70 is plugged directly into one of the channels of the FFT analyzer, pink noise generator y'd into the other input of the dual channel FFT, I get a flat response that is in polarity.
2. Wire the two identical mics directly to the dual channel FFT, one channel using the above mentioned Countryman phantom power supply, then other mic sourcing phantom power directly from the preamp to the dual channel FFT, I get a flat response that is in polarity.
These mics are part of a matched set, within a fraction of a db of each other, with compensation curves applied so one can measure a flat response comparing the two without anything in between. I even swapped them out for another known pair that tested good.
I'm suspecting a wiring issue between the WA310 adapter and the phantom power adapter? Maybe the phantom power adapter doesn't like the unbalanced connection on it's output?
Would love to hear your thoughts/advice on this.