Can anyone give me some information as to what this sort of interference might be?
(Attached are two screenshots from a brief iZotope RX-5 sample of a session I recorded last night.
One shows the interference as a somewhat continuous (there is some amplitude modulation) frequency at 1kHz, with overtones at 2, 3, and 4 kHz. There are additional harmonics that get quieter as the frequency goes up and so are difficult to see on this example.
The second screenshot is the same sample, using a feature of RX-5 that allows one to select the fundamental frequency, and then select for the overtones too. Here , it is easy to see additional harmonics at 5, 6, 7, 8, 9, and 10kHz. The frequencies are very specific.
A little background, the rig is an Apogee Ensemble Thunderbolt into a MacBook Pro into ProTools. I was running eight channels of audio, using a Neumann KM-184 pair and AKG C414 pair and C451 pair condenser mics, a Sennheiser M-88, and an Electrovoice RE-20. Mics and cables were all on a medium size stage. The mic and cable that were bringing the interference to the recorder was off on the left side of the stage, 5-10 feet from other cables.
I use the rig all the time without seeing this sort of interference. On Friday, I used the rig in one location, and Saturday in another (same everything; mics, cables, etc.). There was no interference on Friday and on Saturday, it there was.
I also believe I have seen the interference at the same venue in the past.
iZotope RX-5 fixes the issue without killing a lot of time, and in this situation, the result is unnoticeable.
My question is; what does this look like to you?