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Dynamic mic hum?

 
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Jim Barton
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PostPosted: Wed Apr 06, 2005 7:52 pm    Post subject: Dynamic mic hum? Reply with quote

Every now and again I use an EV RE20 for "high intensity" voiceovers. It sounds great, but I'm plagued by a hum. I can reduce the gain of the hum by turning the mic around or moving it up and down, but I can't get rid of the hum totally. (This also happens with my Shure SM7.) My preamps are an HHB Radius 40 and an ART Dual MP, and I have the same problem with both of them. Of course there's no hum when I use condenser mics.



Any suggestions? Thanks,
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kgenus
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PostPosted: Wed Apr 06, 2005 8:11 pm    Post subject: Reply with quote

It may be the computer monitor ... does it happen when the monitor is turned off?
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billelder
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PostPosted: Thu Apr 07, 2005 2:56 am    Post subject: Reply with quote

Jim,



When you connect the RE20 do you have it in the same configuration as you listed in the "audio chain" thread?

Quote:
...into HHB Radius 40 preamp/compressor, into PowerMac G3


Can you describe what the hum sounds like? Is it an electrical type midrange "buzz" or a low pitch hum? (Maybe a 'rama lama ding dong' in there somewhere?) Does it sound audio or power related?



I had the hardest time tracking down a hum that was coming from a local television cable provider that had a floating ground loop on the utility pole. I solved the problem by canceling the cable and getting DirecTv. <g> Like Kevin suggests, have you tried another amp to monitor? Maybe use headphones (if you're not) to see it the hum is speaker or jack related? The other thing is to start changing out cables, switching jacks (doesn't the Fat Man only have one XLR input?) and unplugging equipment.



I have to say that I've never had a hum problem with anything but my RCA 77...but it doesn't like being close to CTR monitors because of its wiring. Have you turned off your computer monitor to see what that does?



Really sorry for the problem you're having. I have a Studio Projects mic that I really love, but nothing beats the RE 20 for those "in your face" spots.
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Jim Barton
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PostPosted: Thu Apr 07, 2005 4:46 am    Post subject: Reply with quote

Thanks Kevin and Bill!



I haven't had an opportunity to do any tests yet (dang, you guys stay up late/get up early!) but will later on today.



The funny thing is, with these "in your face" spots, you never hear the hum anyway because there's never any space between lines. But still, when I send raw v-o to a producer I feel somewhat embarrassed with this amateurish noise in between takes.



Later,
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Charlie Channel
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PostPosted: Thu Apr 07, 2005 8:14 am    Post subject: Reply with quote

Check grounding of all your plug-in components.



You may be experiencing a ground loop problem. I found that a plug that did not have an earth ground had a 3 prong socket. When I moved everything over to a properly grounded plug, the ground problem went away.



Oh, and one other thought: are you hearing the hum through your speakers? I went on one wild hum chase only to discover that my powered speakers were adding the hum, rather than the recording gear. So, it's best to verify that there actually is hum being induced on the recorded signal, rather than only on the playback.



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Jim Barton
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PostPosted: Fri Apr 08, 2005 12:33 pm    Post subject: Reply with quote

I finally had time to test some of your suggestions.



Sure enough Kevin, turning off the monitor removed much of the hum, leaving what I suspect is a faint 60-cycle hum. I haven't figured out how to record with the monitor off, though. I also replaced the mic cable with a higher quality cable that I had in storage.



I'm certain my problem is that I'm in a small room with all the equipment within 3 feet of the power sources. My Mac and power amp are in the other room (my speakers are not powered.) As I mentioned in previous posts, 90% of the time I'm using condenser mics and the hum isn't an issue. Hopefully I can remember to turn the mic on its axis to minimize the hum, and my clients will remain forgiving.



Thanks everyone for weighing in!
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Charlie Channel
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PostPosted: Sun Apr 10, 2005 8:38 pm    Post subject: Reply with quote

Are you using an LCD or CRT monitor? If not LCD, consider testing your rig with one.



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Jim Barton
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PostPosted: Mon Apr 11, 2005 4:30 am    Post subject: Reply with quote

Charlie Channel wrote:
Are you using an LCD or CRT monitor? If not LCD, consider testing your rig with one.



CC




Charlie:



Had I known that a CRT monitor would add hum, I would have considered ponying up the extra cash for an LCD when I replaced my monitor a few years ago. Not in the cards now.



Thanks for the thought,
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kgenus
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PostPosted: Mon Apr 11, 2005 10:05 am    Post subject: Reply with quote

Yeah, it's a common problem, Jim, so much so pretty much every plugin vendor has a plug that will remove it, at what cost to your original audio is the question....
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Art
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PostPosted: Sun May 01, 2005 11:29 am    Post subject: Reply with quote

Jim:



You don't specifically mention that you did, so I'll pop up here and remind you that you need to turn off your phantom power when you're using the dynamic mic.



Not sure how likely that would be to contribute to hum, but I'm sure it couldn't help if the mic was biased with DC.
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