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Considering removing ground from sub snake https://mail.karaokescene.net/forums/viewtopic.php?f=1&t=11023	Page 1 of 1

Author:	LondonLive [ Mon Oct 01, 2007 7:52 pm ]
Post subject:	Considering removing ground from sub snake
I'm considering de-soldering pin 1 from one end of a sub snake that is used to connect the monitor mixer from the main snake running to the mixer for the mains. I understand that this will prevent a possible ground loop (eliminate low cycle hum)but may also magnify outside interference. Has any one tried this and if so what was your experience.

Author:	Keith02 [ Tue Oct 02, 2007 7:27 pm ]
Post subject:	Re: Considering removing ground from sub snake
Lift the shield/ground pin at the downstream end of the cable, not at the source. That should solve ground loop and prevent EMI.

Author:	LondonLive [ Tue Oct 02, 2007 7:56 pm ]
Post subject:	Re: Considering removing ground from sub snake
Keith02 @ Tue Oct 02, 2007 11:27 pm wrote: Lift the shield/ground pin at the downstream end of the cable, not at the source. That should solve ground loop and prevent EMI. The downstream end was where I was considering de-soldering, can I assume if I remove the ground from the source end the shield may act as an antenna? By the way, thanx for the reply, I figured it would be you or Lonnie that would have some input for me. One other thing, when you make XLR cables do you ground the jacket to pin one like they used to in the days of old?

Author:	Keith02 [ Wed Oct 03, 2007 3:04 am ]
Post subject:	Re: Considering removing ground from sub snake
Yes, to all the above. In 1982, it became AES standard to assign pin 1 as shield on XLR connections. I have a trick I use....Make your self a couple of short 6" XLR patch cables with the shield lifted on one end....They come in handy whenever you experience a loop...Just insert them as required/when required. Don't ever lift ground on mic tho. It can be deadly.....Patch cables only!

Author:	LondonLive [ Wed Oct 03, 2007 3:53 am ]
Post subject:	Re: Considering removing ground from sub snake
Quote: I have a trick I use....Make your self a couple of short 6" XLR patch cables with the shield lifted on one end.... Great Idea, a nice little insurance policy. I'll be heating up the soldering iron tonight for a little workout in creativity. Thanx for all the help.

Author:	karyoker [ Wed Oct 03, 2007 8:25 am ]
Post subject:	Re: Considering removing ground from sub snake
I have strung miles and miles and miles of antenna, rf, vide, and audio cables I would never dream of lifting the ground on any of them. Any electrical device esp in a public application according to code has to be at earth ground. (power surge lightning etc). There is a huge difference between earth ground and signal ground. If you have a loop then solve the problem with common grounding. Lifting grounds is an unprofessional band aid and it will lead to further problems downstream and possible total destruction of sensitive equiptment. BTW it is not a snake... With my snake I run 3 mics back audio to the mains audio to the stage monitor and video to the graphics flat screen. If somebody wanted to lift the ground on it I would come unglued I am the only one that can set up directly under WWV in co and not get RFI in the system Along this this part of the road the high power signal kills vehicles with computerized ignitions... Ollie Smith BSEE Engineering Solutions,, No more retired

Author:	Lonman [ Wed Oct 03, 2007 12:14 pm ]
Post subject:	Re: Considering removing ground from sub snake
I agree to not lift the ground. Very unsafe, there is a reason it is there. It would suck if one of your singers were singing and a surge of power shot through the system & zapped them. There are safe alternatives to remove the hum, Ebtech Hum Eliminator being one.

Author:	Keith02 [ Wed Oct 03, 2007 2:03 pm ]
Post subject:	Re: Considering removing ground from sub snake
Just so ya know, they make XLR connections with a switchable shield lift......AND some pro audio gear has a pin 1 lift switch/button near the connection........But that kinda stuff is for pro's who know when/where it is ok to use same .......Line level SIGNAL to outboard gear is one such place....The switches are there to correct ground loop hum, not curcumvent proper equipment grounding. The key word is "shield", not ground conductor...... Off top of me head, the DBX 160 stereo compressor has a pin one lift switch on it's XLR inputs....DUH.

Author:	LondonLive [ Wed Oct 03, 2007 5:27 pm ]
Post subject:	Re: Considering removing ground from sub snake
The way I understand it is that if my mains mixer is 100 feet away plugged into one AC circuit and my monitor mixer is plugged into another AC circuit (because its 100 foot away on the stage where it should be.) I use a splitter snake, yes I said snake it was a snake in 1985 when ProCo made it, it was a snake yesterday and it will still be a snake tomorrow. Anyway, it is possible because of using two circuits that a possible ground loop could develope between the two mixers, so removing the shield contact from one end will alleviate the situation without endangering any vocalist because the mic is still grounded via the shielded line going back to the mains. I suppose transformers could be used but I don't really see the need in the application I'm inquiring about. So am I incorrect in I don't see any danger to the vocalist? Everything would still be intact (pin 1,2,3 and jacket from the mic back to the Allen & Heath. I'm not talking about removing the ground from the AC line.

Author:	Keith02 [ Wed Oct 03, 2007 8:29 pm ]
Post subject:	Re: Considering removing ground from sub snake
Keep it simple and don't be skeered. All your line level patch cables are AUDIO with or without SHIELDS which also serve as AUDIO grounds. THAT's audio stuff, not mains power. Each component is 110VAC and should have it's own chassis ground(three prong plug)and each wall outlet should be bonded to a common that feeds back to the mains. Whenever you feed outboard gear off different 110VAC circuits you take a chance the chassis grounds might seek a bleed to ground via your audio shields/grounds. When it does, it injects 60Hz hum in the audio....not good and safe and easy to fix. So just make sure not to clip the 110VAC 3 prong grounds....... then lift pin 1 as required. Also toss an outlet tester in yer gig bag and check each outlet to insure it is wired properly with ground and polarity. Remind The Lonman that his favorite brand of amp(Carvin) comes with pin 1 lift switches on their inputs.

Author:	LondonLive [ Wed Oct 03, 2007 10:59 pm ]
Post subject:	Re: Considering removing ground from sub snake
Thanx Keith, I have carried a pretty yellow circuit tester for many years . I'm going into a club I've never been into before in the near future, and I already have a meeting setup with their electrician to see what I have to work with there. It always makes me nervous when going into the unknown. Most of the gigs I do have been return engagements for years. It kind of ticks me off when the word "unprofessional" comes bouncing out off left field. I take what I do very serious, and use the best gear I can. (QSC, Yamaha, Rane, DBX, JBL, ProCo, Whirlwind, Lexicon, Roland, Allen & Heath etc) When I'm not sure about something, I ask questions. I've learned a lot in the 35 years I've been doing this and I suspect I will learn more before it's over. I went to the "Rane" site and even they list that although removing the shield from pin one is not their preferred method (it is their 3rd choice) it is by all means safe and acceptable if need be. I consider Rane to be a reputable manufacturer. In any case, Thanx again for all the help. I'm proceeding with caution

Author:	Keith02 [ Thu Oct 04, 2007 3:46 pm ]
Post subject:	Re: Considering removing ground from sub snake
Yes, Rane has some EXCELLENT tech notes available on their site. What many KJ's overlook is the fact that we are dealing with pro audio gear, and we MUST have the same knowlege and experience as any live band soundman to pull off a good sounding show.... A good KJ needs to wear two hats....He's gotta be both the normally "invisible" sound geek, and also the highly visible non-geek looking host. Whenever you hit an equipment problem at a gig there are some definate no-no's, and there are some possible safe fixes.....The secret is to know the difference so that the show can proceed without delay and nothing gets damaged.

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