Ferrite and power line filters?

gurumonkey · Post by **gurumonkey** » Thu Dec 03, 2009 9:13 pm

anybody ever use ferrite to help cut down on noise? how about power line filters?

i'm trying to track down a radio signal that keeps ending up in my mac and it's driving me nuts! i've use adapters out the wazoo.

i just ordered some of each of the above and was curious how they might have worked for you.

Tone Deft · Post by **Tone Deft** » Thu Dec 03, 2009 9:37 pm

ferrites are for power surges, not radio interference.

are you hearing the actual radio station or are you hearing weird noises?

ethios4 · Post by **ethios4** » Thu Dec 03, 2009 9:43 pm

How do you know it's "in your mac" and not in your speakers? I'm wondering if the problem might be unbalanced connections, non-grounded outlets, etc.

gurumonkey · Post by **gurumonkey** » Thu Dec 03, 2009 9:55 pm

i'm hearing the actual radio station

i have no idea where it is coming from, but what i am trying to do is use a mixer to hook a mic into the input for talking over skype. i can't use my firewire port for my audio card because i need it for the camera in this instance. i have a small interface for using with my camera that i've tried using as a mic pre, and i also my m-audio profire 2626 can run in stand alone mode. i can pick up the signal and get it in, but not without radio or tv or whatever the audio actually is.

tone, here is an article that led me to believe that ferrite could be a possible solution http://www.stevelarkins.freeuk.com/comp ... erence.htm

ethios4 · Post by **ethios4** » Thu Dec 03, 2009 9:59 pm

How is your mixer connected to your interface? XLR, 1/4" unbalanced, 1/8", etc?

Tone Deft · Post by **Tone Deft** » Thu Dec 03, 2009 10:10 pm

you're hearing a radio or TV station. think it through... TV and radio stations are encoded before transmitted, then they have to be decoded for you to hear them.

AM can be decoded with a single diode. FM is more difficult to decode. IMO it's likely that you're hearing noise from a TV or radio, noise that's AFTER it's decoder, it's not your gear picking up the station, it's getting noise from a TV or radio. go around turning your TV and radios OFF, see if that cures it. AM can be decoded simply, it's possible that your gear is setup in some way to mimic a basic AM decoder circuit but I'd start with the obvious things first.

beyond that, a Fuhrman power conditioner should help. as that article said, doing multiple winds around a ferrite might help. dunno, I've never had to do that, in designing electronics I put ferrites on some inputs to chill inrush currents.

I'd start with as simple of a setup too. turn on only the bare minimum to hear audio, then turn on one piece of gear at a time to see if you can find the one thing that's letting noise in.

as always, check your grounds and try to put your stuff on the same power circuit in your home (on the same circuit breaker.)

ethios4 · Post by **ethios4** » Thu Dec 03, 2009 10:11 pm

Good thoughts, Tone

gurumonkey · Post by **gurumonkey** » Fri Dec 04, 2009 3:36 am

i shall investigate further, but i can tell you that i have no tv. i do have a stereo receiver next to my computer but even with it unplugged i could still pick up noise.

gurumonkey · Post by **gurumonkey** » Fri Dec 04, 2009 3:57 am

ethios4 wrote:How is your mixer connected to your interface? XLR, 1/4" unbalanced, 1/8", etc?

my mixer is connected directly to the mac's input.

so what i have is an xlr microphone connected to either a small video mixer or my m-audio profire 2626 running in standalone mode. if it's the profire, i've tried leaving output one which carries the signal from input 1 and i've tried leaving through the headphone jack too. i've tried tons of things with this. the latest was leaving through a balanced cable, then using a converter to get from 1/4" to 1/8". then i thought maybe somehow it was bad to have a TRS connector going in, so i changed it to a 1/8" TS. alas. i do notice that if i just connect the computer to the mixer or profire, things don't start to get signal until i plug in the mic cable. doesn't matter if there is a mic or not on the other end, and doesn't matter if the gain is up on the device. am i just connecting it wrong? that's what i've assumed, but everything i've tried hasn't worked at all.

okay. tried one more thing, and it seems to work. my video mixer is battery operated. it has a mic out that takes an 1/8" TRS to an 1/8" TRS. when i used this cable i seem to get no noise. before i was trying to use an rca cable to connect it, with lots of variations, but mostly using an rca stereo to 1/8" TRS to get from the output, and another on the other end to get in. must have made a loop or something. i have yet to try a call on skype, but my mac seems to show a clean signal coming in now.

nothing i do can make the profire work right.

i'll keep seeing if this works.

gurumonkey · Post by **gurumonkey** » Fri Dec 04, 2009 4:01 am

one more development...
the cable that goes from the battery power mixer is only 6 or 8" long, so i put a longer cable on (it's 20ft) and now i get radio like crazy. hmmm. so maybe i just need to keep it short.

ethios4 · Post by **ethios4** » Fri Dec 04, 2009 5:03 am

I'm not absolutely sure, but I think that fits with having an unbalanced cable. When you ran the balanced cable you stuck a 1/4>1/8 converotr on the end that probably made the whole thing unbalanced. That's why you were getting so much interference with the longer cable. The short cable is probably unbalanced also, but it's so short it doesn't matter much. That's my theory anyway.

ethios4 · Post by **ethios4** » Fri Dec 04, 2009 5:06 am

Also, do you have proper gain structure? You should try having the mic's channel on the mixer turned up as high as you can without clipping, then have the mixer's master turned up as much as you can without clipping. This will feed the hottest signal into your mac so that you don't have to use its preamps which are probably noisy. Something to try...

leonard · Post by **leonard** » Fri Dec 04, 2009 8:09 am

yes everone use it

crumhorn · Post by **crumhorn** » Fri Dec 04, 2009 12:41 pm

What type of mic are you using? If it's a high impedance type and it's connected to a high impedance input then you will pick up all kinds of crap.

gurumonkey · Post by **gurumonkey** » Fri Dec 04, 2009 1:31 pm

ethios4 wrote:That's why you were getting so much interference with the longer cable. The short cable is probably unbalanced also, but it's so short it doesn't matter much. That's my theory anyway.

yea, i'm sure that the cables are unbalanced since they are sending a stereo signal. one must be left, one must be right, the other ground. so i suppose that is it. I'll test more.

crumhorn wrote:What type of mic are you using? If it's a high impedance type and it's connected to a high impedance input then you will pick up all kinds of crap.

the mic i have is an sm57.

Ferrite and power line filters?

Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?

Re: Ferrite and power line filters?