Audio input problems

Elvis Deane

Elvis Deane

Active member
On a shoot about a week ago, I noticed that I was getting a lot of static and picking up a radio station when I had my audio set to Input 1. Switching to Input 2 had no such similar effect. Thought it was just something about the location or the line I had plugged in, but now I'm 100 kilometres away and I plugged in a shotgun mic- same thing. Static when set to Audio Input 1, none when I switch to Input 2 or the internal mic.

Anyone have any ideas? I'm guessing this is likely a thing I have to bring the camera to Panasonic to fix.
 
FYI, a bad or dirty connection or cable can act as a radio antenna and pick up radio transmissions.
 
XLR cables are notorious for picking up radio AM noise. My dad was a broadcast engineer and told me how back in the day they would go through a lot of them as the shielding would break down. Some lengths are more susciptibe than others since they start acting like antennas, and AM frequencies can bounce so you don't have to be right next a transmitter. Try a new cable, short as possible. You may be able to find shielded cables, but they are usually not as flexible and a bit harder to find. Report back as we would all like to know if that solves it. BTW I sometimes shoot in a hospital with a ton of EMF and radio noise. The XLR inputs sometimes struggle, but my Rodelink wireless lab has always worked. Go figure....
 
Ya, try a new cable. And not just a cheap Hosa or similar cable from some music shop. Perhaps one made with Canare or Belden star-quad cable. And maybe even with Neutrik's EMC XLR connectors:

http://www.canare.com/ProductItemDisplay.aspx?productItemID=53

http://www.neutrik.com/en/xlr/xlr-cable-connectors/emc-series/

Not voodoo; those EMC connectors really do seem to provide a solid RF shield in tricky conditions.

Also, I'm assuming you can just replace a mic cable. Are you mainly having trouble with a shotgun mic, or are you trying to plug in other stuff? What model mic? Is its connector good and tight?
 
After more experimenting, it has to be something internal. It happens when nothing is plugged into Input 1. Input 2 is clear as day. If I'm on Line for input one, there's silence. If I turn it to Mic I begin to hear static, and if I give it phantom power, the audio levels on screen start moving very far up (past the halfway mark).

Not sure what's changed inside the body in the past two weeks, but I guess I'll have to bring it into Panasonic for repairs.
 
Well, if you can hear an AM station, a ground point inside can be broken, causing a transistor (base-emitter for example) acting as a diode, demodulating the AM signal. Another possible cause is a faulty tantalum condenser in the input stage...
Anyway, if it is as you describe, I think Panasonic service has to repair it. Please let us know what is (or than was) the cause...
Thank you.
 
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