hum when B3 plugged in at DVinfo.net

Renton Maclachlan · August 4th, 2011, 04:13 AM

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.

Steve House · August 4th, 2011, 04:23 AM

Quote:

Originally Posted by Renton Maclachlan

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.

Renton Maclachlan · August 4th, 2011, 05:13 AM

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.

Rick Reineke · August 4th, 2011, 10:14 AM

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.

Greg Miller · August 4th, 2011, 07:26 PM

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)?

Jon Fairhurst · August 4th, 2011, 11:51 PM

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.

Renton Maclachlan · August 5th, 2011, 02:55 AM

Quote:

Originally Posted by Greg Miller

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...

Greg Miller · August 5th, 2011, 07:49 AM

Quote:

Originally Posted by Renton Maclachlan

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?

Renton Maclachlan · August 8th, 2011, 05:04 AM

Quote:

Originally Posted by Greg Miller

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...

Greg Miller · August 8th, 2011, 08:40 AM

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.

August 4th, 2011, 04:13 AM	#1
Renton Maclachlan Trustee Join Date: Jul 2007 Location: New Zealand Posts: 1,180	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.

August 4th, 2011, 05:13 AM	#3
Renton Maclachlan Trustee Join Date: Jul 2007 Location: New Zealand Posts: 1,180	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.

August 4th, 2011, 10:14 AM	#4
Rick Reineke Inner Circle Join Date: Aug 2008 Location: New York Posts: 2,038	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.

August 4th, 2011, 07:26 PM	#5
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,786	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 4th, 2011 at 11:24 PM.

August 4th, 2011, 11:51 PM	#6
Jon Fairhurst 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

August 8th, 2011, 08:40 AM	#10
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,786	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.