Topic: Interference Problem (What's this noise?)

[huskerdu]

I'm guessing this is cell phone interference. Can I eliminate this by some sort of shielding? I'm running Neumann KM-184->Sound Devices Mixpre-> Edirol R-09HR. I've had this same noise for my past two shows.

http://www.sjtaper.com/music/jwh/jwh_noise.wav

[crazifyngers]

that sounds like cell phone interference to me.  I have only ever heard this with gsm phones.  I have also heard it more often when running 2g.  but gsm and 2 g is just anecdotal.  keep cell phones that are turned on away from your rig.  while it is almost never possible to remove it completely i found that it is worse when using unbalanced cable.  do you keep your phone in your gearbag?  or right next to it?

[12milluz]

Definitely cell phone interference. While balanced cables will help, you will still get it. It is getting into your setup somewhere where there is little shielding. It happens with my studio monitor in my home studio and I use balanced cables. I'd say just keep phones away, its really your best bet.

[huskerdu]

I don't even bring my cell phone into the venues any longer, but so many people are texting and Twittering from the audience these days.

[it-goes-to-eleven]

You haven't provided much specific information on your cables, etc.

As others have stated, if you see someone trying to use a cellphone near your rig, smash their phone.  Don't bother asking them to move away.  Just take it and smash it.  That is the reason so many tapers carry the heavy Shure A27; phone smashing.

The question is... Which component of your rig was impacted by the phone?   You need to do some home testing to try and reproduce the problem.   We get surprisingly few reports of interference on this site.  Curiously, Most that I've read involve the marantz 660...

I've been very nervous around cell phone users when running my r09, but have yet to experience any interference.  So I wouldn't necessarily assume it is the unbalanced cable (though the specific cable could be an issue).

And... some phones are worse than others.  Could be you were next to a bad one... or your cables are too long, etc.

[huskerdu]

You haven't provided much specific information on your cables, etc.

I have 10' balanced AT XLR cables (AT8314-10) from the mics to the Mixpre and a 2m 1/8' mini Monster cable from the MixPre to the Edirol. I was running the mics about 8' high, so I had some cable coiled on the floor. I know the AT cables aren't the best...should I upgrade them?

[jnorman34]

yes, that is indeed cell phone.  i have heard that there is a certain type of neutrik connectors that are recommended to help reduce that - i will look back in my stuff for that reference and post it here if i can find that again.

got it:
"In any case, John Willetts recommendation of Neutrik's EMC connectors is
correct. They are usually quite efficient.

Finally, the first and most simple remedy can be assuring that in both
cable connectors the shield is connected to both Pin1 and Pin0 (the housing
latch inside the cable connectors.)"

[huskerdu]

yes, that is indeed cell phone.  i have heard that there is a certain type of neutrik connectors that are recommended to help reduce that - i will look back in my stuff for that reference and post it here if i can find that again.

got it:
"In any case, John Willetts recommendation of Neutrik's EMC connectors is
correct. They are usually quite efficient.

Finally, the first and most simple remedy can be assuring that in both
cable connectors the shield is connected to both Pin1 and Pin0 (the housing
latch inside the cable connectors.)"

Thanks Jim...I'll look into that. I love the Nuemanns, btw!

[huskerdu]

It looks like these may do the trick: http://www.cbicables.com/ShieldSeries.htm

[huskerdu]

RFI was a problem with these mics that was addressed in a circuit board change in units manufactured shortly after mine were made. The response from Neumann:

Hello Bill,

pity, the change started with KM184 ser.nos. 264xx. So yours are from 1999/early2000.

As RFI & EMC are "lovely" topics there is no simple circuit modification which would help. One has to exchange the complete pcb. Spare part number is #82658. Our international distributors can provide them as standard spare parts.

Alternative procedures:
1. Make sure that your cables have Pin1 + housing pin (Pin0) connected together, preferably in both XLR cable connectors, in *any* case inside the female XLR connector. If not, you have approx. 2 inches of unshielded connector right at the entrance of the mic.

2. You might test the fully shielded Neutrik EMC connectors.
http://www.neutrik.com/fl/en/audio/204_1330328617/XCC_Series_productlist.asp
x

3. Even better are
http://www.neutrik.com/en/en/audio/204_1603252336/EMC-XLR_Serie_productlist.
aspx

A quick test with mobile phone at 2 inches from the female XLR end gives you roughly :
- Neutrik XCC: 15 dB improvement
- Neutrik EMC-XLR: 20 dB improvement
- New circuit / pcb: 35-40 dB improvement

Now, it depends on how "seriously infected" your recording situations are which if the above will be the best solution for you. Having a few Neutrik EMC cables lying around is quite helpful in any case.