XL1s audio - popping and static - onboard + XLR
 

I just wrapped up my first three day shoot with a new XL1s and MA200 XLR adapter/shoulder pad. I recorded using the following setup:

12bit four track audio
Stereo 1 L/R : Canon on board stereo mic
Stereo 2 L : Sennheiser K6+Shotgun combo (powered)
Shotgun cabled via XLR connectors into the MA200 unit

In preshoot testing I found that there were no problems with the setup. About half the footage is fine, but the other half has significant popping and static on the recording (audio only, video is clean and clear). The problem does not get progressivly worse (some of the later footage is clear, some isn't, etc.), nor does it seem to be consistent (thus not simple equipment failure).

It is heaviest on the right channel of Stereo 2, where there should be no audio at all (that xlr input was left unconnected). It is noticeable, though fainter, on the left channel of Stereo 2 (the Sennheiser coming in via the XLR cable) as well as on the on board canon stereo microphone. This is what confuses me. Could it be some electrical issue being introduced on the right channel input somehow that then impacts the other 3 audio tracks????

If it was consistent this answer might make sense, but it really comes and goes. Sometimes seems to be related to the audio level of the recording (according to the meter I'm not clipping the audio). To clarify, the audio isn't distorted, but there is clicking and popping introduced to the channels in the proportions mentioned above.

I do have the XLR audio levels set to the maximum on all inputs, due to lower level of the Sennheiser.

Any feedback welcome. This is my first real experience shooting with the XL1s, and on top of this I am still getting up to speed with audio issues, so no information is too basic for me.


Reproducing this problem: I ran some post shoot tests to see if I could reproduce the problem, but haven't been successful yet. Cables don't seem to have any problems (they are new and I checked them with a meter... no apparent shorts). Considering that 6 out of 12 tapes had this audio problem, and some of the other half dozen had sporadic popping, I am sure it will crop up again, hence this call for ideas!

Thanks...

-Ethan
Hong Kong

A few questions. On playback, is the click/pop there if you use analog audio output or just with firewire? During playback in the XL1, is it always at the same points on the video? If you capture to a .WAV file, can you isolate the waveform at the pop/click and determine what it looks like using a sound editing program?

Loud pops in a right channel of the MA-200 could crosstalk into other channels, but I would expect it to be down at least 40 dB or more. But the obboard mic does not go through the MA-200, so that is a puzzlement.

I'm preparing to do a test capture now via firewire, and will check the waveform on all channels. The on board mic being impacted is what really confuses/concerns me as well.

When playing back through the XL1s, the clicking and popping is always at the same points in the audio (thus apparently a record problem rather than a playback problem) and the 'clean' footage is always clean on playback.

I'll post more info here after I test capture.

-Ethan
Hong Kong

Cause
 

I tracked the cause of the problem to one of my mic cables. While it tested out properly on the meter, when recording it seems to be the cause of the clicking and popping.

However, I still am unclear why a short in this cable would cause cross talk over to all other three channels. It really sounds loudest on the right channel on Stereo 2 that had no input.

Which program are you using to capture?

The clicking and popping is playback to a video monitor. I capture to Premiere (though am considering moving to DVXpress - a different forum topic).

Intermittant shorts and opens in cables can cause strange ground currents and spikes that might induce signals in the other channels.

Thanks! That's what I was looking for. That cable is going in for repair.