Gremlins

July 30, 2013

Phantom

When preparing for a recording session, I go through a fairly extensive checklist to make sure that all aspects of the signal chain are in order. I start with the acoustic space — the room itself — if I am recording with microphones. I check to make sure that the signature of the room and the specific tracking area will not get in the way of a good recording.

From there it is making sure that the microphone choices are good ones and that the microphones are deployed, connected and line checked. Microphone, cable, preamp, DAW, monitor system and any outboard.

A few days ago, I had issues with a basic signal chain: Neumann KM-184 -> Mogami Cable -> API 3124+ -> Avid HD IO 16×16 -> Neve 8816 Summing Mixer -> Pro Tools HD and Cue System.

For whatever reason, two Neumann KM-184s exhibited strange asymmetric clipping with volatile readings off the API meters. All of the other microphones for the session were fine.

I checked the voltage that the API unit was sending out via the four microphone inputs. Each one measured 48.1VDC. Okay, so the Neumanns should be happy. That level of phantom power is about as close to 48V as possible.

I was going to check the mics out on a different set of preamps but decided to do some test recording instead.

No issues. Everything clean and clear. No asymmetrical clipping of the waveforms. No internal microphone noise. No volatile meter readings.

Gremlins.

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