Eliminating radio station interference in recording studio

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jackercrack
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Eliminating radio station interference in recording studio

Postby jackercrack » December 25th, 2012, 8:40pm

Hi there,

I have a studio space on Exchange street in the Larkin District. I am suffering from the issues of having radio stations (mainly Wyrk 106.5) coming in through various sources. The major culprits are guitars/basses with active electronics, jacked up condenser mics, etc.

I tried a monster power 2500 with the 2 stage clean power thing and it seemed to help some but I'm not positive...because it's intermittent. I have also tried putting extra copper shielding into a strat...which seems to have made it worse.

As far as I can tell the earth ground is good...but I'm in a building with a bunch of factory equipment...so the power probably isn't super clean.

I'm at a loss now and I'm not sure how to proceed. Just wondering if anyone in the downtown area has sorted this out. I've had the same problem at other places downtown with various equipment/setups so i think it's more geographical then anything...ie: the radio station is right downtown.

Not sure if I should try working on cleaner power, or Faraday cages or what.

Any input would be helpful.

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Re: Eliminating radio station interference in recording stud

Postby jtsound » December 27th, 2012, 12:22pm

It can really suck downtown depending on the location. I've done sound at pretty much all the downtown venues and have run into this problem at most of them. The upstairs stage at the Lafayette Tap Room when it was on Pearl St may have been the worst though. It didn't help that most of the people playing there were using vintage instruments and amps but even modern equipment wasn't immune to the interference. I don't know how many times I had to listen to these old touring blues guys at the Tap Room or the Tralf bitching about the country music blasting through the amp and saying that they have traveled the world with that amp and haven't had a problem anywhere but here. The Thursday at the Square stage was bad too if I remember correctly.

Good grounding and clean power is a good start but that won't help you with a poorly maintained instrument, amp or patch cabling. You have to try and narrow down where the weak link is that is letting the radio interference in and the problem is that it can also be a combination of things that is creating the tuned circuit that will act as an antenna. It may be that the 20' guitar cable is combining with the tone circuit and pickups of a certain guitar or bass and the fuzz pedal to be a perfect length of copper that picks up a radio station. Changing one of those things may help but it may take removing or replacing 2 or more things until you see improvement.

Swap out cables and try a different guitar for starters to see if you can pinpoint the problem. If you narrow it down to a guitar you can ground the cavity with foil tape or paint but you must make sure that you have a ground path to the jack ground. Try to use balanced cabling wherever possible.

I found that there was no one solution that worked on every rig and sometimes nothing that I had available to try worked at all.

I built a High freq filter circuit into a DI that I used inline on guitar and keyboard rigs, that worked sometimes. I ran cables through ferrite chokes and that worked sometimes. I kept a few Canare Starquad cables around of different lengths and that worked sometimes as well. There were times when I used every trick in my book on the same rig at the same time and nothing worked. Usually that meant that the input circuit on the amp was the problem and unless you could convince the performer to use a different amp then we just had to live with the radio that night.
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Re: Eliminating radio station interference in recording stud

Postby jackercrack » January 8th, 2013, 11:09pm

That's BS.

It's my understanding that if the radio stations are doing the right thing...and the electric company is doing the right thing, etc...this shouldn't happen.

I actually filed a complaint with the FCC and, surprisingly enough, they got back and said it was because I as using consumer grade electronics and I should switch to professional electronics...

The room in question is supposed to be a recording studio...which makes it difficult because the gear changes for each customer. Active electronics and pedals are the worst culprits.

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Re: Eliminating radio station interference in recording stud

Postby 4fingers » January 14th, 2013, 12:00pm

This may sound a bit crazy, but try suspending as much of your cabeling off of the floor as you can. This goes for speaker as well as instrument and mike cables. I live near radio transmitting towers and had a major problem with this. For some reason, hanging the cables and preventing them from touching the floor worked well for me. ??? Being a "practice space", looks did not matter. It's a shot, but may help.
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Re: Eliminating radio station interference in recording stud

Postby jackercrack » January 30th, 2013, 2:56am

Interesting update... I noticed the meters moving on my presonus studio live when only a cable was plugged in...no Mic. So I turned the volume way up and I could hear the radio station very clearly. What was interesting...is that I could move the cable around and I could tune it to at least two other radio stations. One was definitely 106.5 WYRK Country, one was an playing 3 Doors Down...so maybe the Edge or Jack FM (don't listen to a ton of radio so not sure of the formats in town), and a third station I couldn't identify. With it picking up several different stations...I'm starting to think again that it may be bad grounding or some other problem further up the line as opposed to stations broad casting over their limits. It is especially bad on anything with a circuit board...active electronics, newer condenser mics. Reverb tanks are terrible...but makes sense though...they're the perfect antennas :)

Gonna to some more testing on the actual electrical wiring and see where that leads me. Looking in to RF blocking paint...really expensive but seems like it will definitely fix the issue.

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Re: Eliminating radio station interference in recording stud

Postby jackercrack » January 30th, 2013, 3:03am

4Fingers. Is your practice space on the first floor? It may make sense that picking your cables up off the ground would help because I was reading that Earth ground literally displaces it's voltage on the top layer of the ground and that it can actually travel in to your body...so maybe your cables were picking up interference from the actual Ground.

I'm on the 4th floor...so I don't think it will matter...but it might. They could be picking up something from the ceiling of the floor below...I'll check it out. Anything is better than having to re do a take to move stuff around to reduce Shania Twain in the background :) Generally it's not even noticeable in the scheme of a marshal running on 11...but for voice over work it's a major PIA.

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Re: Eliminating radio station interference in recording stud

Postby jtsound » January 30th, 2013, 10:49am

jackercrack wrote:Interesting update... I noticed the meters moving on my presonus studio live when only a cable was plugged in...no Mic. So I turned the volume way up and I could hear the radio station very clearly. What was interesting...is that I could move the cable around and I could tune it to at least two other radio stations. One was definitely 106.5 WYRK Country, one was an playing 3 Doors Down...so maybe the Edge or Jack FM (don't listen to a ton of radio so not sure of the formats in town), and a third station I couldn't identify. With it picking up several different stations...I'm starting to think again that it may be bad grounding or some other problem further up the line as opposed to stations broad casting over their limits. It is especially bad on anything with a circuit board...active electronics, newer condenser mics. Reverb tanks are terrible...but makes sense though...they're the perfect antennas :)

Gonna to some more testing on the actual electrical wiring and see where that leads me. Looking in to RF blocking paint...really expensive but seems like it will definitely fix the issue.


Sounds like your Presonus has crappy CMRR specs as well as maybe some questionable grounding. Or you are just using really bad mic cabling. A balanced cable plugged into a decent mic input circuit should give you good rejection of RF interference, much better than even a great unbalanced guitar or line level circuit. I guess if you crank the gain high enough you will eventually get to hear some interference on even the best cables and input circuits.

Try getting your hands on better cabling and also try a different length of cable since what the cable is doing is electrically combining with whatever you are plugging it into and creating a tuned circuit with the cable acting as the antenna. Changing the length of the cable will tune the circuit to a different frequency and might tune it out of range of the stations, could make it worse though too but it's worth a try. You could also try using an outboard mic pre for critical stuff and use a line level input out of that into your board. Even an inexpensive outboard unit might have better RF rejection at the input circuit level.

Good equipment and good cabling should keep the interference out of the heart of your rig, it always worked for me even in the worst venues I worked downtown. I could always count on my rig to be clean thanks to logical and well built AC distro, high quality cabling and professional equipment. All bets were off as soon as I started plugging in the bands equipment though.
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Re: Eliminating radio station interference in recording stud

Postby 4fingers » January 31st, 2013, 7:19pm

jackercrack wrote:4Fingers. Is your practice space on the first floor? It may make sense that picking your cables up off the ground would help because I was reading that Earth ground literally displaces it's voltage on the top layer of the ground and that it can actually travel in to your body...so maybe your cables were picking up interference from the actual Ground.

I'm on the 4th floor...so I don't think it will matter...but it might. They could be picking up something from the ceiling of the floor below...I'll check it out. Anything is better than having to re do a take to move stuff around to reduce Shania Twain in the background :) Generally it's not even noticeable in the scheme of a marshal running on 11...but for voice over work it's a major PIA.



That makes sense to me. We practise in the basement which would underscore that idea. I have also had some problems blowing out a few PA channels, when I (used to ) wear sneakers and happen to touch my mike stand. I heard a loud "snap", and the mike channel blew out. Grounding is everything I guess.
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Re: Eliminating radio station interference in recording stud

Postby 99devils » February 18th, 2013, 12:14am

jtsound wrote:
Sounds like your Presonus has crappy CMRR specs as well as maybe some questionable grounding. Or you are just using really bad mic cabling. A balanced cable plugged into a decent mic input circuit should give you good rejection of RF interference, much better than even a great unbalanced guitar or line level circuit. I guess if you crank the gain high enough you will eventually get to hear some interference on even the best cables and input circuits.


I also have a studiolive an I also have problems picking up radio stations in the Elmwood Village. I can hear some radio station interference even with the mixer off and just the power amp on, and I get interference in my guitar amp too. I haven't noticed if there's a difference in my guitar with active electronics versus the others. I've always thought it was shitty power.

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Re: Eliminating radio station interference in recording stud

Postby IndiProAudio » February 19th, 2013, 2:18pm

The problem is likely poor design and poor shielding of your condenser microphones and active instrument pickups. Radios are very basic electronic circuits and essentially get made accidentally inside cheap or under engineered equipment. Adding to the the issue is the Radio towers being close by, while they are likely following FCC regulations, all bets are off when you are camped right on top of them. I would try using better Microphones and RF shield your active instruments. The power itself is not likely the problem but checking all your grounds might help. Cables lying on the floor are not problematic unless there is something emitting RF or EMF from something in the floor itself.

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Re: Eliminating radio station interference in recording stud

Postby TobaccoSoup » November 11th, 2013, 11:44am

Every single cable and conductive component (resistor, capacitor, etc.) acts as a tiny antenna. It doesn't help matter that the large radio transmitters are dumping their trash into ground, and at much larger swings than your gear. Again, verify you have good grounds at your service outlet - get an electrician if you need one.

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Re: Eliminating radio station interference in recording stud

Postby Kyle B » January 3rd, 2014, 1:06am

Every cable acts as an antenna. Good 'wall ground' isn't going to get you where you want to be. The impedance of house wiring is too high for it to be an effective RF sink. The RF in your neighborhood is way too strong for such a simple cure. You will need to be more proactive. The only practical action you can take (besides moving to the suburbs) is to filter your cables.

If you wisely select an appropriate clamp-on ferrite choke, you can eliminate the interference. These guys demonstrated exactly what you're dealing with: http://audiosystemsgroup.com/SAC0305Ferrites.pdf They show how to pick the appropriate core, but ultimately you still have to do some experimenting.

It's tough reading, but try it. You only need to understand their conclusions, not the theory or method behind it (these guys must be engineers - they just can't get straight to the point ;) ) The bottom line is this CAN be solved if you're persistent.

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Re: Eliminating radio station interference in recording stud

Postby TobaccoSoup » January 14th, 2014, 10:14am

That was a good read, thanks KyleB!

Still, good grounds help the shields/drains do their thing. Once I get my 'freak-out' room operational again, I'll see if I find RFI down here on the lower west-side (somewhere between WGRZ, WIVB and WNED, can't recall where the radio transmitters are anymore).

Good cabling cannot be over-emphasized which is why it was assumed. Chassis grounds may also be factor. More often than not, quality gear, cabling and good ground schemes have solved my RFI issues for audio.

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Re: Eliminating radio station interference in recording stud

Postby TobaccoSoup » July 29th, 2014, 4:03pm

Well, the 'freak-out' room has finally been set-up (temporarily) and the main system is RFI free (even with amps at full) without any power conditioning...until I listen through my headphones through a crappy/cheap-O Fostex headphone amp. I agree with the FCC...upgrade. One piece of garbage in your signal chain can ruin the entire works.

There's a reason poor equipment is cheap and good equipment is expensive, and RFI/EMI is one of the corners that are cut in most designs I'm afraid to say. Just reference the median salaries for experienced RF engineers and you might see why this is so (not that an RF engineer is required, but they may be consulted by better equipment manufacturers)...


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