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Tips & Techniques:Gefell Owners w/ Noise Problems - the FIX!

If you've ever had RF or grounding problems with your Gefell's, you need to read this.

I bought 9 used Gefell's in mint condition about 6 months ago (late 80's/early 90's vintage) and have had intermittant strange grounding and RF noise with all but one of them. Out of the 9 mics, (UM70's, M71S's, 692/M70's), 8 of them were mildly to radically problematic, and strangely enough 1 was always OK. (Strangely enough, the mid numbered mic in a series of consecutive serial #'s.) AND ONLY IN MY PARTICULAR STUDIO. Everywhere else they were OK. All my other condensers, ribbons and dynamics are fine at my studio - ZERO problems. (Neumann, AKG, GT, Shure, Audix, EV, Sennheiser, etc.)

I tried everything. Got many suggestions here. None worked out. They still had noise interference depending on the phase of the moon, their physical location in the studio, the weather - whatever. To make things worse, a session with them could start out OK - noiseless - and noise would eventually creep in as the session wore on. Aargggh! I really liked them, but was growing to hate them.

I talked with Jim Williams and he told me that they were junk and told me to off them on ebay. But I didn't want to give up on them yet cause I dug their sound, so I kept hunting for a solution. I don't want to get into all the details about everything I tried right now (it would become a small book if I did), but a search would give you the background.

Anyway, I talked with a scoring engineer buddy of mine and he did some research for me and talked to a guy that made "pigtail fixes" for gefell's.

Bottom line, it's a weird grounding issue. The simple fix is as follows, and if you have a problematic Gefell, I'd suggest you try this out :

On the Female XLR that plugs into the mic, you remove the shield (Pin 1) and tie it to the little loop on the chassis of the plug at the top. (Switchcraft style) Voila!! I tried it and was amazed. It dropped the noise floor into the basement and made the mics useable again. Needless to say...I am one happy camper. I've had no problems since implementing the pigtail adapters.

File that away in case you ever have a problem with your Gefells at another studio. Well worth soldering up a few pigtails just in case.

Cheers,

bp

PS - be sure to click on "Discussion" below for an interesting take on the "issue" from Neumann. Seems they have had similar problems with certain Neumann mics as well.

Contributors: mw, drBill
Created by drBill, 27th January 2008 at 10:16 PM
Last edited by mw, 27th March 2012 at 03:05 PM
Last comment by JEGG on 7th March 2008 at 03:41 PM
1 Comments, 10,252 Views



(1) Comments for: Gefell Owners w/ Noise Problems - the FIX! Page Tools Search this Page
Old 7th March 2008
  #1
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Mic grounding and RF issues

When I started reading, I knew where the answer was going.

Neumann series 180 mics (and some others) were particularly prone to RF interference-especially cell phone and some grounding issues-before they changed their electronics to address that problem.

BUT-until that time, Neumann's standaard refrain (which did work!) was:

Be sure to connect the XLR shell(s) of the mic cable to the screen (of the mic cable)-and ESPECIALLY at the mic end. Reason being: Purely mechanical connections and metal "abutments" will test just fine for continuity, but they may behave very differently at RF frequencies.

The Gefell solution is one I'll add to my repertoire-and I'm curious if this would have worked with the Gefells.
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