hum when B3 plugged in at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old August 4th, 2011, 05:13 AM   #1
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
hum when B3 plugged in

Just setting up for a shoot tomorrow and trying out various mics.

I have a JuicedLink 231 with two mics connected to it (one an Rode NT3), connected to a Panasonic GS400 camera. The other mic for recent shoots has been a Rode pin mic which has been fine.

Tonight I thought I would try the Countryman B3 I have because of simply being able to clip in onto a woman talent who will be off camera. I have only used this mic once before and there was no issue with hum (in an auditorium with long leads). However tonight (in my studio) there was this significant hum through the phones which went away (more or less) when I touched the headphone jack or XLR mic connector. I thought it was the phone jack, but there was no hum through the phones when the Rode was plugged in, making me suspect its something to do with the B3. It occurred on both 12v and 48v phantom power, but not with phantom turned off.

Any ideas?

Thanks.
Renton Maclachlan is offline   Reply With Quote
Old August 4th, 2011, 05:23 AM   #2
Inner Circle
 
Join Date: Mar 2005
Location: Hamilton, Ontario, Canada
Posts: 5,742
Re: hum when B3 plugged in

Quote:
Originally Posted by Renton Maclachlan View Post
Just setting up for a shoot tomorrow and trying out various mics.

I have a JuicedLink 231 with two mics connected to it (one an Rode NT3), connected to a Panasonic GS400 camera. The other mic for recent shoots has been a Rode pin mic which has been fine.

Tonight I thought I would try the Countryman B3 I have because of simply being able to clip in onto a woman talent who will be off camera. I have only used this mic once before and there was no issue with hum (in an auditorium with long leads). However tonight (in my studio) there was this significant hum through the phones which went away (more or less) when I touched the headphone jack or XLR mic connector. I thought it was the phone jack, but there was no hum through the phones when the Rode was plugged in, making me suspect its something to do with the B3. It occurred on both 12v and 48v phantom power, but not with phantom turned off.

Any ideas?

Thanks.
Hate to ask the obvious but how is the B3 set up? Is it hardwired to an XLR/Phantom power supply or are you using some sort of adapter with a vesion that is wired for a wireless transmitter? Have you checked for faulty dimmers, etc, in your studio? The fact that touching the case makes diminishes the hum makes it sound like a grounding issue.
__________________
Good news, Cousins! This week's chocolate ration is 15 grams!
Steve House is offline   Reply With Quote
Old August 4th, 2011, 06:13 AM   #3
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: hum when B3 plugged in

Thanks Steve. It's hard wired to the JuicedLink via XLR cable, and powered by phantom power.

I've just done some tests. Contra earier post, the hum doesn't go away if I touch the phone jack. But it does lessen if I hold the XLR connection - which has a preamp in it apparently. Put the connection down and it increases.

But wait, there is more. If I put the mic close - right up close - to a tripod or a light stand or a metal bracket I've slung off the wall to carry a light, it hums like crazy. The lights were not on and thus no dimmers were functioning.

No hum at all if I put the mic close to the JuicedLink.
Renton Maclachlan is offline   Reply With Quote
Old August 4th, 2011, 11:14 AM   #4
Trustee
 
Join Date: Aug 2008
Location: New York
Posts: 1,840
Re: hum when B3 plugged in

This sounds like a transformer or AC power line radiating a magnetic field that the mic cable is picking up.
Try running a star-quad XLR extension cable... Or finding the offending transformer and/or AC cable and moving it.
Rick Reineke is offline   Reply With Quote
Old August 4th, 2011, 08:26 PM   #5
Trustee
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 1,359
Re: hum when B3 plugged in

The XLR adapter that the mic is plugged into... is it a proper Countryman device, or some third-party adapter that's not made specifically for that mic?

What happens if you leave the XLR adapter plugged into the XLR extension, which goes to the JuicedLink; but unplug the B3 from the adapter?

Also, is it a hum (mostly sinusoidal in nature)? Or is it a buzz (with a lot of harmonics)?

Last edited by Greg Miller; August 5th, 2011 at 12:24 AM.
Greg Miller is offline   Reply With Quote
Old August 5th, 2011, 12:51 AM   #6
Inner Circle
 
Join Date: May 2006
Location: Camas, WA, USA
Posts: 5,513
Re: hum when B3 plugged in

Ditto about the Countryman XLR adapter.

I bought a Sanken COS-11D and tried a generic adapter. It didn't work at all. I ended up using the Sanken adapter and it works perfectly. Each pigtail lav seems to have it's own special needs, when it comes to powering them from a phantom supply.
__________________
Jon Fairhurst
Jon Fairhurst is offline   Reply With Quote
Old August 5th, 2011, 03:55 AM   #7
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: hum when B3 plugged in

Quote:
Originally Posted by Greg Miller View Post
The XLR adapter that the mic is plugged into... is it a proper Countryman device, or some third-party adapter that's not made specifically for that mic?

What happens if you leave the XLR adapter plugged into the XLR extension, which goes to the JuicedLink; but unplug the B3 from the adapter?

Also, is it a hum (mostly sinusoidal in nature)? Or is it a buzz (with a lot of harmonics)?
The b3 mic is connected by its wire to the custom Countryman xlr plug which I believe has a preamp in it. The two are permanently connected and cannot be separated. This xlr plug just connects straight to an xlr lead which runs in my case to the JuicedLink, and on to the camera.

The b3 can be powered from 9v>48v phantom power when hardwired.

Is it a hum or a buzz? I would say a hum, but I will have to listen to it again to confirm that.

I have just done a shoot this afternoon using the PinMic and the NT3 and there was no issue whatever...
Renton Maclachlan is offline   Reply With Quote
Old August 5th, 2011, 08:49 AM   #8
Trustee
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 1,359
Re: hum when B3 plugged in

Quote:
Originally Posted by Renton Maclachlan View Post
The b3 mic is connected by its wire to the custom Countryman xlr plug which I believe has a preamp in it. The two are permanently connected and cannot be separated. This xlr plug just connects straight to an xlr lead which runs in my case to the JuicedLink, and on to the camera.
OK, thanks for clarifying, you have the permanent XLR version, not a "wireless" version with the XLR adapter.

Yes, I think you are picking up capacitively coupled noise from the AC mains. But that shouldn't happen, at least not to any troublesome extent. I suspect some sort of problem with grounding/shielding of the mic wiring. I hope it's not a problem in the B3's cabling, since you have the permanently wired version.

1.) What happens if you plug the B3's XLR plug directly into the JuicedLink, without any intermediate XLR extension cable? If that fixes the problem, then you've got a problem with your XLR extension cable.

2.) Are you sure the body of the XLR connector is connected to shield, and not just floating?

In retrospect, I realize we have a very incomplete picture here. Two more key details are missing:

3.) In addition to the hum, do you still hear audio from the B3, or is the mic itself dead?

4.) What is the level of the hum, relative to the normal level of the mic?

Last edited by Greg Miller; August 5th, 2011 at 01:55 PM.
Greg Miller is offline   Reply With Quote
Old August 8th, 2011, 06:04 AM   #9
Trustee
 
Join Date: Jul 2007
Location: New Zealand
Posts: 1,104
Re: hum when B3 plugged in

Quote:
Originally Posted by Greg Miller View Post
OK, thanks for clarifying, you have the permanent XLR version, not a "wireless" version with the XLR adapter.

Yes, I think you are picking up capacitively coupled noise from the AC mains. But that shouldn't happen, at least not to any troublesome extent. I suspect some sort of problem with grounding/shielding of the mic wiring. I hope it's not a problem in the B3's cabling, since you have the permanently wired version.

1.) What happens if you plug the B3's XLR plug directly into the JuicedLink, without any intermediate XLR extension cable? If that fixes the problem, then you've got a problem with your XLR extension cable.

2.) Are you sure the body of the XLR connector is connected to shield, and not just floating?

In retrospect, I realize we have a very incomplete picture here. Two more key details are missing:

3.) In addition to the hum, do you still hear audio from the B3, or is the mic itself dead?

4.) What is the level of the hum, relative to the normal level of the mic?
OK, I just got to do some more tests...

1. The mic is working.
2. The hum is present when the Countryman XLR plug is straight into the Juicedlink.
3. The hum is very loud in the above situation (xlr > JL), when the mic is held.
4. The hum virtually disappears when the mic is is held very close to where the xlr connector enters the JL.

Re no 2 of Gregs questions: I do not know. It is effectively brand new so should be, if it's meant to be.
RE no 4: The volume of the hum varies as to where the mic is, and is held.

Perhaps I should contact Countryman...
Renton Maclachlan is offline   Reply With Quote
Old August 8th, 2011, 09:40 AM   #10
Trustee
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 1,359
Re: hum when B3 plugged in

Renton, if I understand you correctly, when the B3 is plugged directly into the JL, you get "some" amount of hum.

If you then touch the mic, the hum level increases significantly, and is significantly loud relative to the mic's audio output level.

I would try only a few more things, for the process of elimination.

1.) Move everything... mic, mixer, etc., to a different room or even different building... someplace that does have mains wiring (not outside in the middle of a field). Then repeat the test. Is the problem the same?

2.) Try that mic only into a different mixer, preamp, etc. Is the problem the same?

If I had to guess, based on what you've said so far, I would guess that the answers to the two above questions will be "yes." If that's the case, there seems to be something wrong with the shielding/grounding of the B3's cabling, or perhaps the grounding within the preamp/plug.
Greg Miller is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 07:06 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network