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| Re: Radio Frequency Interference (RFI) in Mics [message #268716 is a reply to message #20287 ] |
Sun, 26 August 2007 21:26   |
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 Mike Cleaver
Messages: 258
Registered: August 2004
Location: Vancouver, BC, Canada |
Active Member |
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Your friend here is a simple piece of wire with an alligator clip on each end; probably a couple of them.
Try the different grounding schemes, tying pin one to the shell at one end, both ends, or all ends of the cable.
Every connector you add increases the probability of a noise problem (generated through mis-wiring or a wrong connection scheme)
You have a connector at the console/preamp end, one at the wall going into the studio, another at the wall coming out in the studio then two on the mic cable.
Now, find out where the EMI is coming from.
Start with only the console or mixer or preamp fired up and start switching things in.
If it's coming in on the power line, you'll hear it on the board before anything else is turned on.
Are you in your own building or sharing space with other businesses?
Try some of the above.
Let us know what you find out.
Mike Cleaver Broadcast Services
Vancouver, BC, Canada
Broadcast Studio Design and Consulting
Voiceover Talent
Newscaster
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| Re: Radio Frequency Interference (RFI) in Mics [message #321428 is a reply to message #20287 ] |
Tue, 04 March 2008 14:03 |
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nob turner
Messages: 178
Registered: April 2004
Location: san francisco |
Active Member |
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I have a Neumann TLM193 which is more susceptible to hum than any other mic I own. This is made much more obvious when you touch the basket of the mic--the hum gets significantly louder. I live not far from the tv tower that broadcasts to the entire area.
A message to Neumann USA got a response suggesting that my problem was indeed RFI, and specifically the vertical sync signal from the tv transmissions. They say there is no update to the mic to improve this issue. I have checked out my cables, and they are properly wired and grounded. I've read through this thread, and it appears that chokes would need to be installed in the mic by the manufacturer, if i've read this right. The info on ferrite beads is perhaps a bit beyond my technical understanding. Nonetheless, if there is a possibility that they'd improve my situation, I'd like to give them a try.
Why do you think they call it the control room?
www.garymankin.com
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| Re: Radio Frequency Interference (RFI) in Mics [message #321467 is a reply to message #321428 ] |
Tue, 04 March 2008 15:46 |
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Klaus Heyne
Messages: 1959
Registered: April 2004 |
Platinum Member |
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Before you move to sound-deteriorating chokes and filters:
Are you using Neumann/Gotham GAC 3 cable, where ground and shield are terminated at both ends to pins #1 of the XLRs and to the sleeves of the connectors?
Please double check, as most RFI problems disappear when the above steps are taken.
Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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| Re: Radio Frequency Interference (RFI) in Mics [message #326556 is a reply to message #321467 ] |
Fri, 21 March 2008 21:35 |
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nob turner
Messages: 178
Registered: April 2004
Location: san francisco |
Active Member |
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Yes, Klaus, I've now acquired some GAC-3, wired it as per your above instructions... and the 60-Hz hum is still there.
Keep in mind I am about 2 miles from the Sutro broadcast tower in SF. I've tried patching directly into my mic preamps so as to avoid any other cable in the loop. I've tried three different preamps.
What is the next step?
Why do you think they call it the control room?
www.garymankin.com
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| Re: Radio Frequency Interference (RFI) in Mics [message #326745 is a reply to message #326556 ] |
Sat, 22 March 2008 17:24 |
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Klaus Heyne
Messages: 1959
Registered: April 2004 |
Platinum Member |
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I am sorry that I did not read your post carefully enough. My cable suggestion was in reference to your RFI/radio tower suspicions.
60Hz hum is by definition unrelated to RFI, but is either due to wrong cable terminations, or the mic pre's grounding scheme or a problem in the mic's amp itself. In rare cases, 60Hz hum can already be present in a deficient AC grounding scheme coming to your studio from the power pole/distribution box.
Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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| Re: Radio Frequency Interference (RFI) in Mics [message #327536 is a reply to message #326745 ] |
Tue, 25 March 2008 14:39 |
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nob turner
Messages: 178
Registered: April 2004
Location: san francisco |
Active Member |
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ok, i'm ready to go about checking ground issues... but want to mention that NO other mic in my collection exhibits this problem, including other transformerless mics like km184. the hum increases significantly when i touch the basket of the mic, but NOT when touching other portions of its body or the mic connector. in fact, the hum commences to increase as my hand nears the body, but doesn't touch it. this latter fact was sighted by the neumann tech i spoke to as strong evidence that the problem was rf related.
mean time, i will look again at grounding here.
Why do you think they call it the control room?
www.garymankin.com
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