hum on audio with A/C adapter?

evolvnyc

evolvnyc

Well-known member
I have ruined an entire interview (I think) as my wired Tram tr-50 lav mic, attached to a brand new mogami cable, was apparently picking up a buzzing during the interview (in the headphones, it seemed to be the headphone jack connection, so I didn't think too much of it) HAs this buzzing happened to anyone else when using the dvx100a plugged in and rolling with the A/C adapter? Is there anything to do to avoid this (besides burning through batterries and risking their running out mid-tape?) Any comments appreciated...
 
Trust your phones. A spare set of phones can sometimes confirm stuff like that... I havent had the porblem on the DVX, but if audio cables run too close and parallel to lighting (electrical) cables, sometimes hum can be induced.

The other thing could be that maybe the wall power where you shot was "dirty"?

Just some thoughts..
 
If it's a 60 Hz hum, you might be able to clean it up in post with a notch filter. Maybe at its harmonics, too.

It shouldn't effect the interview's quality...unless you were interviewing James Earl Jones, perhaps.
;^)

Dan
 
evolvnyc said:
I have ruined an entire interview (I think) as my wired Tram tr-50 lav mic, attached to a brand new mogami cable, was apparently picking up a buzzing during the interview (in the headphones, it seemed to be the headphone jack connection, so I didn't think too much of it) HAs this buzzing happened to anyone else when using the dvx100a plugged in and rolling with the A/C adapter? Is there anything to do to avoid this (besides burning through batterries and risking their running out mid-tape?) Any comments appreciated...
Click to expand...

Repeat after me...When do you listen to the audio...always, ALWAYS, ALWAYS.

When do you take the headphones off? When you are not shooting.

Buzz can come from many sources. Your post does not indicate if the buzzing stopped while powered under battery. Is that the case?

Was there anything else you had powered by AC that was plugged into the camera?

Ty Ford
 
Never run audio cables in parallel to ac cables. If they cross they must be perpendicular (like a cross) or they will pick up the energy from the AC cable. And the adapter for the mic must never be near an AC cable.
 
It did only happen when I was running off of A/C. I checked and made sure it wasn't crossing any power cables... There was a monitor which was plugged into the the dvx also, but I have used this same exact set-up over 20 times for hours at a time, and it was this only one time that it happenned... Always with the exact same equipment. I guess it must have been a cross I didn't see? Or I had heard that sometimes running on A/C will just do that. Is there anything to do to if that is the case? Because of my set-up, I can't really wear the phones during the interview.
 
I've seen this happen before with hardwired trams plugged into the DVX running off of AC. The solution is to power the camera off of batteries to completely avoid any potential issues.

-Dave
 
evolvnyc said:
It did only happen when I was running off of A/C. I checked and made sure it wasn't crossing any power cables... There was a monitor which was plugged into the the dvx also, but I have used this same exact set-up over 20 times for hours at a time, and it was this only one time that it happenned... Always with the exact same equipment. I guess it must have been a cross I didn't see? Or I had heard that sometimes running on A/C will just do that. Is there anything to do to if that is the case? Because of my set-up, I can't really wear the phones during the interview.
Click to expand...

Why not? I do it all the time.

Ty Ford

Oh, sorry, do you have a latency problem?
 
yes actually, the echo is really distracting at 24p, and i feel that it puts off the (often elderly) subjects to be speaking to me while wearing headphones... and even these 5000 batterries barely last a 63 minute tape...
 
Then congratulations, you have reached the threshold at which you need another person on your crew. One that listens to the audio to make sure bad things don't happen.

BTW, while you're talking to these folks while not wearing headphones, who's looking through the view finder?

Regards,

Ty Ford
 
Aha, i have a monitor set up that I can watch while talking to people... too bad there isn't an automated sound monitoring machine... *sigh*
 
evolvnyc said:
Aha, i have a monitor set up that I can watch while talking to people... too bad there isn't an automated sound monitoring machine... *sigh*
Click to expand...


Well, there is, actually. A spectrum analyzer would do it for ya... But you'd have to get used to reading it. There are even some software versions of it you could use with a computer.

Or use DV Rack on a laptop to a) monitor image, b) monitor audio, and c) skip using tape and just record to the hard drive. :thumbsup:
 
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