Digital Interference due to HDMI Cable Length

[ADS]

Hello, I recently had come across some kind of digital interference when I was on a shoot. I needed to send audio signal to our clients monitor. I sent out the signal via XLR cable patched into a Canon C70 and from the C70 into a monitor. I noticed the audio started to sound different as I recorded the next few takes and the actors voices started to to sound like there was some kind of electronic interference. I swapped out cables and nothing seemed to change. Only after I unplugged from the camera and restarting the 633 did things start to go normal; after that I no longer sent audio feed. The location space were tight shots that the client could hear the actors delivery of their lines 

 

I have sent an audio signal before to this camera in the past with no problem when we have done live internet feeds. The only thing that I could say that was different was that we were using a 25ft HDMI cable. Whereas the previous shoot the cable was much shorter. 

 

My setup was an NTG3 shotgun mic plugged into a boompole, plugged into a Sound Device 633. Sending out feed via XLR cable into camera, and from there an HDMI cable out from camera monitor to client monitor.

 

Would a wireless feed be a better solution if I needed to send audio feed to a client monitor? My initial thinking was being plugged would be a safer bet and wouldn't have any kind of wireless interference. I know there could've been other factors into play as well. I'm just curious if anyone has heard such a thing or something similar happen to them. 

[edward chick]

Was your 633 recording the noise directly to the tracks? Or were you going by what the client monitor was outputting? Depending on quality of monitor and its input and electronics that could easily be the problem. Was the signal output from the C70 via SDI out or hdmi? SDI outputs are pretty hardy. 

 

Monitors get bashed around and HDMI cables and inputs are not very robust. I would hedge my bet on its a monitor problem and not your 633. How was the camera audio? If cam audio and your 633 are both good, then I would not even bother to worry about it. You might want to invest in a small speaker for such jobs. Get one with XLR inputs. Or invest in listening assist devices like comtek, ifb blue. 

 

[ADS]

1 hour ago, edward chick said:

Was your 633 recording the noise directly to the tracks? Or were you going by what the client monitor was outputting? Depending on quality of monitor and its input and electronics that could easily be the problem. Was the signal output from the C70 via SDI out or hdmi? SDI outputs are pretty hardy. 

 

Monitors get bashed around and HDMI cables and inputs are not very robust. I would hedge my bet on its a monitor problem and not your 633. How was the camera audio? If cam audio and your 633 are both good, then I would not even bother to worry about it. You might want to invest in a small speaker for such jobs. Get one with XLR inputs. Or invest in listening assist devices like comtek, ifb blue. 

 

Yes, the noise was recording directly to the 633. The signal output was HDMI; the monitor only had an HDMI input.

 

I will have the check the camera audio. And yes I have in the past used a small speaker to send a signal there with no issue. Thank you for the recommendation!

[The Documentary Sound Guy]

I'm inclined to say you encountered a one-time glitch with the 633 and it has nothing to do with feeding the camera hardwired or any of the other possible factors you identified.  Since restarting the 633 made the problem go away, I would just leave it at that.

I can imagine scenarios where interference comes back through the XLR cable, but none of them seems as likely to me as a software glitch within the 633 itself.

And, yes, I'd imagine a wireless hop would solve even the potential for interference coming back through the output cable, though, as you noted, wireless comes with its own gremlins.

[ADS]

Just posting this that in the end I had sent the NTG 3 for repairs and it turned out there was an internal issue in the microphone. Received a replacement NTG3 from RODE.