Radio Station Picked Up in U87

[ORecords]

So I just got my first Neumann U87 in today. I've been looking forward to this for quite a while now. I open up the wood case, set it up on the mic stand, plug it into my LA-610, fire up the phantom power, and..... Hear the radio station next door loud and clear.

I've been at this location for over a year now, and while the radio has been picked up occasionally in older guitar amps or pedals, I've never had this problem with any of my other mics. The guy who owned my studio previously had told me he had to have a number of his U87's rewired to avoid picking up the radio, but I blew him off since I hadn't had any difficulties previously. Well, I've fallen out of touch with him now and am not sure who did his work for him.

Any ideas what I should do? I would ideally like to avoid having the mic physically modified, but if that's what it takes, I guess I have no choice. It sounds wonderful otherwise, but it's pretty much unacceptable for use in professional recording sessions in it's present condition.

Thanks!

[dwire]

Since I do not have a U87 siting around, nor do I know your signal chain and amplification of it before it hits the recorder. All I can tell you is that if you are not seeing this at any noticeable rate from other gear, your best bet is going to be within the U87 itself, just as the previous owner did. I am curious, if this is an AM, or FM channel, and have you really evaluated whether or not you are not picking up this channel in everything else, simply perhaps not enough to bother you? Also, food for thought, these days, most stations no longer transmit locally. That is if you are telling me you are beside their studio, not the tower; as now days, most stations use satellite or other methods to get their output signal to the transmission location that is usually out in bum-f*ck.

Look at even our three old emergency broadcast stations in the USA. AM WLW in Cincinnati Ohio has their transmission network, miles from the studios, for the very same reason you are having the trouble you are. And, yes WLW and the other two, that are still the only ones the FCC allows to broadcast at a really high level (higher than anyone else on the dial) they used to be the ones people were hearing in their heads via the right "tuned" sort of dental fillings. I would hate to know what it was like to stand out under their transmission network back in the day when the cold-war emergency system for our country depended on these AM stations to warn everyone of the end, as I am sure you could about microwave an egg beneath their towers... The FCC has ramped them way, way down over the years. Just food for thought, and I know not helpful at all. Believe me, you came to the right place, as someone is probably typing in a relevant answer to your question as I write this little humor column.

Reminds me of the first "studio" I recorded in. I had to borrow an electric guitar I could not play (a Flying "V" design) that I was not used to with active pickups in it, as my crappy axe at the time had passives, and there were major high tension (electrical) transmission lines that ran right outside the rear of the studio. We could not use a noise-gate with my guitar, as the noise from the utility wires was louder than my pickups! Darn EMI!

Good, luck, and when someone does give you the solution, if you are actually beside the transmission area for this station, I would check all of your other gear with a fine tooth comb as well. Just my 2 cents worth...

Best of luck my friend!
dwire

[JohnRoberts]

Check with Neumann. They may have a standard mod to deal with RF rectification.

Large RF signals are difficult for slower components to deal with, but this is not a new problem.

JR

[nosebleedaudio]

try this; make a special cable with the female end of the XLR grounded, pin 1 grounded to the case.
A Switchcraft connector makes this very easy.
Label it on that end "Pin 1 grounded" so you can keep up with this cable.
This works most of the time...

[Jim Williams]

A typical "fix" is to replace the 47 ohm output resistors with a pair of 47 uh inductors, that's a severe fix. Alternatively you can try a ferrite bead in place of the inductor. Another fix is to replace the .022 uf output filter caps with surface mount parts. This was the fix for the Rode NT mics I designed. The lead inductance of these caps can cause rf rectification.

Jim Williams
Audio Upgrades

[dwire]

See, three very excellent responses! Hey Mr. Williams, nice to see you chime in here; good stuff there too. The only one that never crossed my mind for some reason is the "surface mount shuffle" as I have seen and or done the others including the wire up a special mic cable "trick" (not my pick really, but I am really picky about the shielding stuff...) It is so easy for me sometimes to, well as a very senior friend of mine use to say to me, "You can't see the trees for the forest in front of you."

Hope all is well with your business, family and friends. Take care all.

dwire