Audio - I hope I'm posting this in the right spot

I

Indiefilming

Solution for audio ground loop problem?

Hi! I'd love some suggestions here.

We're holding auditions in a new space and I ran into a problem.

I have lights set up (2 china balls with 4 lights in each china ball) with small monitor and camcorder all running on the same outlet.

We're using a battery operated Rode shotgun mic with a 3.5mm mic jack plugged into the mini camcorder for optimal audio.

This set up has always worked beautifully in the past, but in this new space I'm getting ground loop feedback. It's like a hiss or high pitched buzz. When I unplug the Rode mic, the camcorder's internal mic kicks in, the hiss is gone but it's back to the crappy internal mic camcorder audio.

I need to get the Rode working with this system again.

Could anyone recommend a solution? Or recommend a ground loop isolator? I looked up isolators but don't understand how they work with this set-up. I don't have a sound board. The mic is plugged right into the camcorder and I'm not a sound person so I don't speak this language anymore than what I googled to problem solve.

Thanks!!
 
Sort by date Sort by votes
I tried posting in the newbie section because I'm not a sound person. But I'm not sure if I should be posting here instead. I'd be truly grateful for some help with an audio prob for a coming week of audition sessions.

I have my lights and a camcorder and 7" monitor plugged into the same power strip running from an extension cord from the main room into this little studio area.

I have a battery operated Rode shotgun mic with a 3.5mm mic jack plugged into our mini camcorder. I do this because the actor's voice is as important as their face for my partners and myself.

The set up has always worked perfectly in other spaces in the past, but in this new space I'm getting ground loop feedback. A hiss or high-pitched buzz. When I unplug the Rode mic, the camcorder's internal mic kicks in. This takes care of the hiss but then I'm left with the crappy camcorder audio.

I need to get the Rode working again without the buzz/hiss.

Anyone have any suggestions? I looked up isolators and was confused about how to make them work with this set-up. The mic is battery operated and plugs straight into the camcorder so I'm not working with a sound board. We're holding auditions next week and I'm really struggling with this.

Also, in this room are 4 light sockets. Don't know if that effects anything.

Thanks so much for an advice!!
 
Upvote 0 Downvote
The electrical noise in the room is being picked up by the unshielded cable on the video mic. are you using and extension cable? Even the short cable on the mic will pick up noise. XLR mics use shielded cables that protect from noise. There are TONS of threads in this forum about basic audio eqt. Good Luck
 
Upvote 0 Downvote
Which camera?

Which Rode shotgun mic?

Are you using any extension cables or adapters?

Do you have power conditioning? (Not just a power strip with a surge protector. If you can't afford power conditioning you may wan to consider running on batteries only.)

Does this new space have florescent lighting?

Have you tried it with the overhead lights off?

Are there any appliances in the room or nearby?

Is it in a large building?

Are you near an airport or train station or radio tower?

Please give as many details as possible - makes, models, cable lengths, the room, the building, the neighborhood, etc.; be completely anal about it, sometimes that's the only way you can track down problems like that.


I used to play keyboards professionally. There was one club I absolutely hated, as did the sound company. The stage was directly over the electrical room in the basement, and all the conduits for the 20+ story building an right behind the stage. We couldn't use wireless mics or guitars, my sampler never booted up properly, and we had every type of hum and buzz you could imagine. BTW, I had am $800 Furman power conditioner for my rig; the sound company had about five of them and it was still no help.
 
Upvote 0 Downvote
Are you using an AC adapter on your camera? It could just be 60 cycle hum......
If your using anything with a non-polarized plug you can try unplugging it, rotate 180 degrees and plug it back in. Try using a different outlet on another circuit and/or run your camera/audio gear on a different circuit than your lights. You can try ripping off a magnet from an unused USB cord or power adapter and put it on the mics cord...

Thats all I got...
 
Upvote 0 Downvote
Also, if the mic cable crosses any electrical cables, make sure it does so at a 90 degree angle to decrease chances of inductance of the 60 hz interference.

The Video mic is not suited to working in an environment that has anything that throws RF at all... the 1/8" plug has no protection for exposed runs of the cable, so whatever cable comes out of the mic and into the camera becomes an antenna for any RF interference in that environment. Trading up to an XLR system for audio will help get rid of that problem (it's the specific reason I spent to trade up from my ATR55).

Are you using this as a camera mounted mic or a boom mic?

If there are any large (think highschool gymnasium) lights around, fluorescent lights or anything with a motor (ceiling fans/ ventilation systems, refrigeration systems, assembly line belts, etc...) turn them off as they specifically throw RF around the place.
 
Upvote 0 Downvote
Hmmm... Good Ideas

Anim8 & knightly, thanks so much for responding!

I was thinking of picking up a polarity checker from Home Depot.

"run your camera/audio gear on a different circuit than your lights" - I thought running them on different circuits is what caused ground loops, no? That's why I have them all on one...

The mic I have is this one http://light-house-films.com/rental/sound/Rode-VideoMic-Shotgun-Microphone-for-DSLR.html
Mounted to a hot shoe, run off a 9 volt batter and plugged into the mic jack on a mini camcorder. The mini camcorder doesn't have XLR input.

Yes the lights are fluorescent which I need for heat control, but again, I've never had this problem before and I've used this set-up for years at multiple locations. It's been ideal for several reasons. Cost-wise, I'm running the camera and mic all day every day for sometimes weeks at a time, so I need a good quality inexpensive cameras and mics so I can have 2 extras as emergency back-up (I once went through 3 camcorders in 2 days- I overworked all of them).

Has anyone ever tried a ground loop eliminator like this one?:

http://www.google.com/products/cata...sa=X&ei=qKQlT8jXKMKdiQLgxNVq&ved=0CI8BEPMCMAA


Thanks so much!
 
Upvote 0 Downvote
Thanks for the help IndieB and Alcove

Thanks Indie Budget, I'm hoping not to have to replace the mics. I'd have to buy all new mics and new camcorders since I need 2 mics and 3 camcorders handy at all times and the camcorders don't have xlr inputs.

Hey Audio Alcove, how are things?

the mic I'm using is this rode mic:
http://light-house-films.com/rental/sound/Rode-VideoMic-Shotgun-Microphone-for-DSLR.html

Mounted to a hot shoe, run off a 9 volt batter and plugged into the mic jack on a mini camcorder.

It is a large and open building but the room we're shooting in is small and relatively soundproofed. No appliances. Just the lights, camera, 7" monitor and mic run off the battery.

The space is not near any airports or train stations or radio towers as far as I'm aware.

With no power in the room, the hiss/buzz does stop. And if I bring the camera with mic outside the room into the main space the hiss stops immediately. It's only in the shooting room with the door closed.

Have you heard of a ground loop eliminator? If there was one device that would fix this problem, I'd buy it. Not sure if this one is any good. It got great reviews on B&H though one reviewer said it didn't work on their AV camcorder/powered mixer setup...:

http://www.bhphotovideo.com/c/product/365781-REG/Ebtech_HUM_X_Hum_X_Ground_Loop.html


Thanks so much for your help!
 
Upvote 0 Downvote
How far away from the talent is the mic being placed during shooting ? anything over 18" is going to create more problems. If the mic is just popped on top of the cam you are hurting yourself
 
Upvote 0 Downvote
The EBTech is okay, but I get the feeling that it won't solve your problem; there seems to be an RF source in the room that's running through the power outlets, and probably in the "air" as well. My suggestion, as unwelcome as it may be, is to run on batteries exclusively when shooting in that particular room.

One more suggestion is to systematically search for what's causing the hum/buzz. Set everything up with all of the electric off in the room and all of your equipment powered down. With the gear plugged into the AC start powering up each piece of gear one at a time (audio, cameras, lights in that order), and then proceed on to the room lights and other electric sources in the room. This way you'll hear what specifically is causing your hum/buzz problem.

It's also possible that something stupid like cell phones, pads and other wireless devices may be causing your problem, although those are usual "tonal" or "pulsing" sounds rather than hums and buzzes. It could be a combination of one specific light and two cell phones.

If you're using extension cords make sure that they are heavy duty, large gauge, grounded cords. As Knightly mentioned in the other thread electric cables should cross other cables at right angles to reduce the chance of RF interference.

These types of issues can drive you crazy. I have one in my studio that I still haven't been able to eliminate - guitar stomp boxes in the control room. The buzz is always there when the computer is on, but I can't record anything with the computer off. The PITA solution is to run a 25' cable from the guitar into the studio, plug it into the stomp box, and run another 25' cable from the stomp box back into the recording input in the control room. As far as I can figure out the stomp boxes and the computer just don't like being close to each other; maybe it's a hi-tech vs. low-tech snobbery thing. :D

Just FYI, this is what I used as my main power conditioner in my racks on the road:

http://www.sweetwater.com/store/detail/AR1215/

Plus two of these (they plugged into the AR1215):

http://www.sweetwater.com/store/detail/PL8C/

Even they didn't always solve the hum/buzz problems.
 
Last edited:
Upvote 0 Downvote
Just saw the other thread...

I'll give you 7 to 2 that the florescent lights are causing your hum/buzz; they are notorious and, despite building regulations, very rarely installed properly. Shut'em off when you're shooting and you should be okay.
 
Upvote 0 Downvote
Indiefilming said:
Anim8 & knightly, thanks so much for responding!

I"run your camera/audio gear on a different circuit than your lights" - I thought running them on different circuits is what caused ground loops, no? That's why I have them all on one...

!
Click to expand...

I haven't had a chance to read all the responses..but I saw this and will comment on it.

One thing you never do is run any audio equipment on the same circuit as lighting. One of the first things you do when setting up any sort of sound equipment is you make sure it is on a different circuit than lighting.
 
Upvote 0 Downvote
Batteries only and still... noise

Thanks for all the advice. I tried everything you all suggested.

Switched all the fluorescents to incandescent bulbs.

Ran the camera and Rode mic on batteries only.

Tried 2 Rode mics with 3 different cameras, all of which continue to work beautifully together in different locations - any other location than this one it seems.

I even had an electrician come in and shut off all power in the room...

And I'm still getting noise.

I made this little video to illustrate the noise and problem:

http://www.youtube.com/watch?v=L9by2
 
Last edited:
Upvote 0 Downvote
Might try plugging the mic into a pocket digital recorder. I use a $50 Olympus VN8100PC. That would help you determine if it is the combo of the cam & mics or ??? Plugging the Rode into a digital pocket recorder will get you about the same quality as using the on-cam recording.

It was hard to listen for the noise due to the constant handling of the cam creating noise

It sounds like your mic is picking up signals from lights etc. Maybe the combo of the Cam & Mics are the issue with whatever is going on at that location.


Good Luck
 
Last edited:
Upvote 0 Downvote
Have you powered down your(and others') cell phone or similar device? Worth a shot.

And sometimes there are places that you can't fix no matter what you do.

Are you sure that all the equipment is in working order? Have you tried Low-Z mics?
 
Upvote 0 Downvote
That sounds more like a data signal rather than an RF static one... are there any microwave antennas or boradcasty things in/on any of the neighbor's places? Perhaps a wireless security camera setup somewhere around there?
 
Upvote 0 Downvote
Thanks for all your help. Turns out certain areas in Silverlake are the bermuda triangle of audio.

Which is why it's so important to bring your sound person out when scouting locations.

I had to move.
 
Upvote 0 Downvote
You must log in or register to reply here.
Back
Top