Line noise filter

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philchenevert
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Post by philchenevert » November 6th, 2019, 8:09 pm

I am looking for advice on a line noise filter for my recording setup. Basically I have noise level that is probably the background 60 Hz of my home and want to filter it out. Anyone use one or have any advice? And if I buy one where should it be placed in the set up?
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Post by KevinS » November 6th, 2019, 9:25 pm

Probably a dumb question, but could this problem be addressed by Audacity's equalizer? Or perhaps you would prefer going to the root of the problem?
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Post by k5hsj » November 6th, 2019, 11:11 pm

Phil,

If you’re talking about a hardware 60 hz filter, I can’t think one would do a better job than the notch filter in Audacity. Solving the problem at the source is usually preferable to playing catch up with a filter. Have you tried all the usual troubleshooting stuff? Cables are always a prime suspect when it’s 60 hz.

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philchenevert
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Post by philchenevert » November 7th, 2019, 5:53 am

Yes Audacity can reduce this but I am interested in stopping the hum as close to the source as possible. My wire technique is deplorable, running cables every which way and if it works I leave it that way. My interface (a dbx 286) went awry a few days ago and I spent yesterday trying to install a new little interface box. Anyway the hum is there, more like a chatter as a background noise. So I'd like to see if it can be eliminated or reduced closer to the wall that's all while I re run all of my wires and cables and multiple outlet boxes.
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Post by lurcherlover » November 7th, 2019, 7:32 am

Hi Phil

You need to unplug each item, * mic, then interface, and then computer to see where in the chain the noise stops. Are you sure it's 60Hz mains frequency? You can get boxes like the one made by ART but they do not always work. The other possibility is a line transformer but these may not work either. A faulty or very old lead (XLR or other) may be the cause too, and it could also be the mic. Does the mic have a HPF which cut below 80 HZ? This may help if switched on. You could permanently set up your editing software to cut the region (EQ) of 40-80Hz. You need a steep filter of about -15dB per octave or even more.

Do you use a laptop? If so try using it on it's batteries only and unhitch it from the mains.

Some mics have a transformer output which can itself attract hum from the mains. There are so many problems in this area.

Also make sure that you have everything coming out of one mains socket, as the use of more than one mains outlets can cause a circular hum as the two sockets interact at 60Hz.

Also could you upload a short 20 second audio example of this noise?

* Or maybe start to unplug with the computer, then the interface lead, and then the mic and its XLR lead?

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Post by sjmarky » November 7th, 2019, 9:34 am

Definitely a low-cut filter would be of help. Set it at about 80hz. I always use the low-cut filter on my mic plus another in post.

Years ago I got devices to attach to all my cables called a line filter choke. Basically a magnet that clamps around each wire. Very cheap. I was having a problem with rf interference (I suspect it was a HAM radio in the vicinity). Did seem to help.
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Post by philchenevert » November 7th, 2019, 9:56 am

Thanks to everyone. I am buying some of those line filter chokes to start with and checking out the other things. I am also (duh!) moving my power bar that has lots of outlets from UNDER the dbx interface. I never even thought that having it right underneath the interface and wires might cause a problem. A fun day indeed!
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Post by sjmarky » November 7th, 2019, 10:09 am

Definitely. Keep all of your cables well away from power cords, and especially any transformers or chargers.
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Post by DaleInTexas » November 7th, 2019, 4:58 pm

sjmarky wrote:
November 7th, 2019, 10:09 am
Definitely. Keep all of your cables well away from power cords, and especially any transformers or chargers.
Sage advice.. Chased that rabbit years ago.

I now use Furman PL-Plus power conditioners for all my rack gear.
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Post by mightyfelix » November 7th, 2019, 11:50 pm

I hardly understand a single word in this whole thread.

Filing this away in "Things I hope I don't need to know."

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Post by KevinS » November 8th, 2019, 3:45 am

mightyfelix wrote:
November 7th, 2019, 11:50 pm
I hardly understand a single word in this whole thread.

Filing this away in "Things I hope I don't need to know."
Me too!

The one thing I get from it is to keep one's computer cables away from one's power source. So the spaghetti of wires behind my desk is probably a bad thing!
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Post by DaleInTexas » November 8th, 2019, 8:20 am

philchenevert wrote:
November 7th, 2019, 9:56 am
I am also (duh!) moving my power bar that has lots of outlets from UNDER the dbx interface.
Phil,
Another noise-battle I had to eliminate was the transformer hum, from my video monitor. It amazed me how much “other” noise my mic recorded, after I got a properly, acoustically-treated recording environment. My recording PC is outside of the booth, with the monitor being inside. Now, I just power down the monitor, once my recording starts.
Dale
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philchenevert
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Post by philchenevert » November 8th, 2019, 8:32 am

Excellent suggestions from all. Never thought of my monitor being a source ... gotta check that next. :thumbs:
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lurcherlover
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Post by lurcherlover » November 8th, 2019, 9:05 am

DaleInTexas wrote:
November 8th, 2019, 8:20 am
philchenevert wrote:
November 7th, 2019, 9:56 am
I am also (duh!) moving my power bar that has lots of outlets from UNDER the dbx interface.
Phil,
Another noise-battle I had to eliminate was the transformer hum, from my video monitor. It amazed me how much “other” noise my mic recorded, after I got a properly, acoustically-treated recording environment. My recording PC is outside of the booth, with the monitor being inside. Now, I just power down the monitor, once my recording starts.
Dale
This is why I like to record to a standalone recording machine, because it means my computer is away from my recording environment. I also now have a new hight quality recorder (Sound Devices) and this means that one mike which has a transformer output and did give a little hum, now works fine with this machine, very quiet, and it's a great mic which is good on my voice. (It's an active ribbon mic). The quality of the recording with a noise floor of more than -60dB is now pretty much as good as it gets. Other mics also work well, even my Beyer dynamic mic, as the recorder has superb pre-amps giving well over 70dB of very clean gain.

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