Gefell Owners/Users - What you need to know....

drBill · 28th February 2007, 08:40 AM

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

I bought 9 used Gefell's about 6 months ago and have had intermittant strange grounding and RF noise with them. Out of the 9 mics, (UM70's, M71S's, 692/M70's), 8 of them were problematic, and strangely enough 1 was always OK. AND ONLY IN MY STUDIO. Everywhere else they were OK. All my other condensers and dynamics are fine at my studio. (Neumann, AKG, Shure, Audix, EV, Sennheiser, etc.)

I tried everything. Got many suggestions here. None worked out They still made the noise - and intermittent to make things worse. I talked with Jim Williams and he told me that they were junk and told me to off them on ebay. I didn't want to give up on them yet, so I kept hunting. I don't want to get into all the details about what I tried right now, 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.

Basically, on the F 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) I tried it and was amazed. It dropped the noise floor into the basement. It made the mics useable again. Needless to say...I am one happy camper.

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.

Thanks Bobby!

The Byre · 28th February 2007, 09:37 AM

It's not just Geffels that suffer from this problem. There are all sorts of shielding and grounding issues that occur and this gets worse with tube-valve based stuff that uses switched (so-called digital) universal power supplies. These dreadful devices cause similar interference to ground loops, but at all kinds of differing freaquencies that can have you shooting off looking for the fault in all the wrong places.

danasti · 28th February 2007, 03:04 PM

Quote:

Originally Posted by drBill

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.

Basically, on the F 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) I tried it and was amazed. It dropped the noise floor into the basement. It made the mics useable again. Needless to say...I am one happy camper.

Nice - Great information! Thanks for sharing this. It's great for you and the mics that it was such an easy solution and nothing seriously wrong with the internals.

Enjoy them!

mahasandi · 28th February 2007, 03:42 PM

Damn

I sent 2 UM70K'S to CABLETEK .

and after some $$$ (perhpas too much) they replaced the xlr connectors.

this would have been a hell of alot more convienent and less $.

Thanks for this though ,

it's helpful news I hadn't and i'am sure many others

hadn't heard .

C/G · 28th February 2007, 04:30 PM

[quote=drBill;1153433]If you've ever had RF or grounding problems, you need to read this.

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.

Basically, on the F 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) I tried it and was amazed. It dropped the noise floor into the basement. It made the mics useable again. Needless to say...I am one happy camper.

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.

[quote]

Interesting and thanks. I've not encountered any noise yet but if I do I'll do what you suggest. My old MV692 pair run off the old Gefell power supply and 7-pin cables so maybe that is why I have never had noise issues.

drBill · 28th February 2007, 07:00 PM

Thanks guys. I hope it's helpful to some of us at some point in time. I know there are other people who have encountered this, because I had heard rumors of this mod and had talked to those who could never figure their problems out.

It was very curious that almost all the mics reacted the same way. I knew there must be a solution. As weird as it sounds, the above configuration completely solved it and now I'm happy as a clam!

I've never encountered it with any other mics, but I certainly see the possibility out there. The Gefells are well made, but they must have a bizzare grounding scheme going on internally. Maybe using chassis instead of internal ground??

FYI, the mics are most likely late 80's models that are transformer balanced.

Mike Jasper · 4th April 2007, 02:35 PM

Quote:

Originally Posted by C/G

I've not encountered any noise yet but if I do I'll do what you suggest. My old MV692 pair run off the old Gefell power supply and 7-pin cables so maybe that is why I have never had noise issues.

Fortunately, I haven't had any trouble either and I've used the MV692 with Tuchel and phantom power as well as the XLR P48s.

This is EXACTLY what Gearslutz if for. Well, this and my sarcastic jokes.

Good on ya, doc.

Jasper

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Gefell CMV 563/MV 69XX series owners(or anyone interested in MG) step inside.	T.RayBullard	High end	3	23rd November 2006 10:55 AM
Gefell User/Owners - can you help me out!	drBill	So much gear, so little time!	33	15th September 2006 06:16 PM
STC-8 Owners / Users...Q?	jho	High end	10	4th April 2006 10:53 AM
Any Neve 51 series owners or users?	BJohnston	So much gear, so little time!	0	30th January 2006 12:18 AM
Masterlink Owners/Users	ajcamlet	So much gear, so little time!	10	7th October 2003 03:26 PM

28th February 2007, 08:40 AM	#1
drBill Lives for gear Join Date: Jul 2006 Location: So Cal Posts: 3,600	Gefell Owners/Users - What you need to know.... If you've ever had RF or grounding problems, you need to read this. I bought 9 used Gefell's about 6 months ago and have had intermittant strange grounding and RF noise with them. Out of the 9 mics, (UM70's, M71S's, 692/M70's), 8 of them were problematic, and strangely enough 1 was always OK. AND ONLY IN MY STUDIO. Everywhere else they were OK. All my other condensers and dynamics are fine at my studio. (Neumann, AKG, Shure, Audix, EV, Sennheiser, etc.) I tried everything. Got many suggestions here. None worked out They still made the noise - and intermittent to make things worse. I talked with Jim Williams and he told me that they were junk and told me to off them on ebay. I didn't want to give up on them yet, so I kept hunting. I don't want to get into all the details about what I tried right now, 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. Basically, on the F 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) I tried it and was amazed. It dropped the noise floor into the basement. It made the mics useable again. Needless to say...I am one happy camper. 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. Thanks Bobby!

28th February 2007, 09:37 AM	#2
The Byre Lives for gear Join Date: Jan 2004 Location: Highlands of Scotland Posts: 1,079	It's not just Geffels that suffer from this problem. There are all sorts of shielding and grounding issues that occur and this gets worse with tube-valve based stuff that uses switched (so-called digital) universal power supplies. These dreadful devices cause similar interference to ground loops, but at all kinds of differing freaquencies that can have you shooting off looking for the fault in all the wrong places. __________________ http://www.the-byre.com

28th February 2007, 04:30 PM	#5
C/G Lives for gear Join Date: Dec 2004 Location: Canada Posts: 2,803	[quote=drBill;1153433]If you've ever had RF or grounding problems, you need to read this. 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. Basically, on the F 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) I tried it and was amazed. It dropped the noise floor into the basement. It made the mics useable again. Needless to say...I am one happy camper. 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. [quote] Interesting and thanks. I've not encountered any noise yet but if I do I'll do what you suggest. My old MV692 pair run off the old Gefell power supply and 7-pin cables so maybe that is why I have never had noise issues. __________________ ------------------------------------------------------------------------ Colin G. http://www.myspace.com/generalsandmajors

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread:

28th February 2007, 03:42 PM	#4
mahasandi Lives for gear Join Date: Apr 2005 Posts: 678	Damn I sent 2 UM70K'S to CABLETEK . and after some $$$ (perhpas too much) they replaced the xlr connectors. this would have been a hell of alot more convienent and less $. Thanks for this though , it's helpful news I hadn't and i'am sure many others hadn't heard .

28th February 2007, 07:00 PM	#6
drBill Lives for gear Join Date: Jul 2006 Location: So Cal Posts: 3,600	Thanks guys. I hope it's helpful to some of us at some point in time. I know there are other people who have encountered this, because I had heard rumors of this mod and had talked to those who could never figure their problems out. It was very curious that almost all the mics reacted the same way. I knew there must be a solution. As weird as it sounds, the above configuration completely solved it and now I'm happy as a clam! I've never encountered it with any other mics, but I certainly see the possibility out there. The Gefells are well made, but they must have a bizzare grounding scheme going on internally. Maybe using chassis instead of internal ground?? FYI, the mics are most likely late 80's models that are transformer balanced.