My sm57 causes a ground loop.

iankaravas · 29th July 2010

Help!

When I first moved into this apartment I had a bunch of ground issues, but about a year ago I fixed everything by running my computer's power supply cable into nice PS Audio power conditioner. It did the trick, now when I crank my monitors all the way up I get nothing but a smooth "hiss". When I plug in my ZoomH4 via its line output to one of the pre's/line ins on my profire610, I get a nice clean input too, no ground loop "hum". (the zoom gets its power from an external supply / batteries )

HOWEVER, when I use my 57/58 I get a serious ground loop running through my whole system, you can only hear it when you really drive the preamps, and unfortunately, that's necessary to record acoustic guitar with a 57. When I move the mic around the room, the amount of hum changes, the instant I unplug the mic, the hum goes away. I've tried XLR ground lifts on the sm57 at the preamp, and at the microphone output jack, neither helped.

Basically this makes my 57 useless. The fluctuating hum drives me insane. sounds like a buzzing bee.

>.<

iankaravas · 29th July 2010

I've been suffering for this problem for over a year, and a monoprice cable fixed the problem!

ALL HAIL MONOPRICE!

THIS IS THE MOST GLORIOUS DAY OF MY LIFE!

SCREW YOU LOCAL MUSIC STORE XLR CABLE! BURN IN HELL!

iankaravas · 29th July 2010

ah crap. It came back now, its much better than before, but still loud enough to drive my nuts.

it never ends

Michael_Joly · 29th July 2010

A dynamic microphone, by definition, can not cause a "ground loop" - it does not have a source of power which could have a "ground" at a different potential to "earth ground" than the preamp it is connected to.

The problem you are experiencing is induced AC field pick up - not a ground loop.

iankaravas · 29th July 2010

Quote:

Originally Posted by Michael_Joly

A dynamic microphone, by definition, can not cause a "ground loop" - it does not have a source of power which could have a "ground" at a different potential to "earth ground" than the preamp it is connected to.

The problem you are experiencing is induced AC field pick up - not a ground loop.

thanks for the reply. I did some searches but couldn't find much. If you could tell me a little bit more, or point me in a direction I would greatly appreciate it.

thanks!

Jack Luminous · 29th July 2010

It's not a ground loop, it's electro-magnetic interferences picked up by the coil in the microphone motor. There's not much you can do about it apart from moving to another place.

Kiwi · 29th July 2010

The method of earthing the shield can be significant. I'm not sure that off-the-shelf mic cables always do this properly. Maybe get an ohmmeter and see if the body of your mic is actually connected to ground. There are several ways of wiring XLR shields - I get confused.

AFAIK - the plastic mic shield on an SM57 is a known weakness acknowledged by Shure. Obviously plastic can't be connected to ground and therefore can't shield the mic coil from that direction. The SM58 is better in that regard. Otherwise, use condensers. Or get an SM7B that has a hum-cancelling coil in it - but even they can pickup some hum.

Kiwi · 29th July 2010

Quote:

Originally Posted by iankaravas

I've been suffering for this problem for over a year, and a monoprice cable fixed the problem!

ALL HAIL MONOPRICE!

THIS IS THE MOST GLORIOUS DAY OF MY LIFE!

SCREW YOU LOCAL MUSIC STORE XLR CABLE! BURN IN HELL!

he he - nice to hear somebody else who is as passionate as me about NOT hearing hum ...

FLZapped · 29th July 2010

Quote:

Originally Posted by Michael_Joly

A dynamic microphone, by definition, can not cause a "ground loop" - it does not have a source of power which could have a "ground" at a different potential to "earth ground" than the preamp it is connected to.

The problem you are experiencing is induced AC field pick up - not a ground loop.

I was thinking this too. Probably should check for high EMF fields.

nosebleedaudio · 29th July 2010

Its the SM-57, its NOT a high end Dynamic..
Try a AT ATM-610..Or get a SM-81 or equiv. for Acoustic Gtr..
I did a test on GS a while back showing the noise floor of a good mic pre with two different mics and a 150 load, the Dynamic was a SM-57, it had a low level hum, using a different and better dynamic it went away...

KAJI · 29th July 2010

Maybe you could get a hold on a ferrite bead that you can attach to the XLR. I have never tried it but I believe this is why some AC power cables have one, and you can find them on some USB cables.

Just an option.

iankaravas · 31st July 2010

Quote:

Originally Posted by KAJI

Maybe you could get a hold on a ferrite bead that you can attach to the XLR. I have never tried it but I believe this is why some AC power cables have one, and you can find them on some USB cables.

Just an option.

I've got a ton of ferrite clip-ons from when i was first trying to fix this problem about a year ago, they didn't do anything unfortunately :[

so this is the sm57? I just find it odd because I never hear anyone talking about this when they recommend them. I guess its caused by some of my neighbors electronics because the problem always goes away at around 1 or 2 am.

nosebleedaudio · 1st August 2010

Quote:

Originally Posted by iankaravas

I've got a ton of ferrite clip-ons from when i was first trying to fix this problem about a year ago, they didn't do anything unfortunately :[

so this is the sm57? I just find it odd because I never hear anyone talking about this when they recommend them. I guess its caused by some of my neighbors electronics because the problem always goes away at around 1 or 2 am.

Most use the SM-57 for louder sources; snare, small toms, gtr amps...
Here's another thread:
SM57 buzz/hum issues

Another thread I started to compare noise levels in different rooms with different mics, the SM-57 was used..There is hum...
Mic pre Noise test with/with out mic.

29th July 2010	#1
iankaravas Gear maniac Join Date: Jun 2009 Location: brooklyn ny Posts: 265 Thread Starter	My sm57 causes a ground loop. Help! When I first moved into this apartment I had a bunch of ground issues, but about a year ago I fixed everything by running my computer's power supply cable into nice PS Audio power conditioner. It did the trick, now when I crank my monitors all the way up I get nothing but a smooth "hiss". When I plug in my ZoomH4 via its line output to one of the pre's/line ins on my profire610, I get a nice clean input too, no ground loop "hum". (the zoom gets its power from an external supply / batteries ) HOWEVER, when I use my 57/58 I get a serious ground loop running through my whole system, you can only hear it when you really drive the preamps, and unfortunately, that's necessary to record acoustic guitar with a 57. When I move the mic around the room, the amount of hum changes, the instant I unplug the mic, the hum goes away. I've tried XLR ground lifts on the sm57 at the preamp, and at the microphone output jack, neither helped. Basically this makes my 57 useless. The fluctuating hum drives me insane. sounds like a buzzing bee. >.<

29th July 2010	#10
nosebleedaudio Lives for gear Join Date: Jun 2005 Location: Birmingham, AL USA Posts: 3,536	Its the SM-57, its NOT a high end Dynamic.. Try a AT ATM-610..Or get a SM-81 or equiv. for Acoustic Gtr.. I did a test on GS a while back showing the noise floor of a good mic pre with two different mics and a 150 load, the Dynamic was a SM-57, it had a low level hum, using a different and better dynamic it went away... __________________ Mike Keith www.jmkaudio.com

29th July 2010	#11
KAJI Gear nut Join Date: Sep 2005 Location: Montréal, Canada/ Bogotá, Colombia Posts: 125	Ferrite bead Maybe you could get a hold on a ferrite bead that you can attach to the XLR. I have never tried it but I believe this is why some AC power cables have one, and you can find them on some USB cables. Just an option. __________________ "We want to hear the grass grow...." - George -

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29th July 2010	#4
Michael_Joly 3 + infractions, forum membership suspended. Join Date: Nov 2005 Location: Cape Cod Posts: 2,735	A dynamic microphone, by definition, can not cause a "ground loop" - it does not have a source of power which could have a "ground" at a different potential to "earth ground" than the preamp it is connected to. The problem you are experiencing is induced AC field pick up - not a ground loop.

29th July 2010	#6
Jack Luminous Gear maniac Join Date: Sep 2004 Location: Paris Posts: 258	It's not a ground loop, it's electro-magnetic interferences picked up by the coil in the microphone motor. There's not much you can do about it apart from moving to another place.

29th July 2010	#7
Kiwi Lives for gear Join Date: Feb 2009 Posts: 2,571	The method of earthing the shield can be significant. I'm not sure that off-the-shelf mic cables always do this properly. Maybe get an ohmmeter and see if the body of your mic is actually connected to ground. There are several ways of wiring XLR shields - I get confused. AFAIK - the plastic mic shield on an SM57 is a known weakness acknowledged by Shure. Obviously plastic can't be connected to ground and therefore can't shield the mic coil from that direction. The SM58 is better in that regard. Otherwise, use condensers. Or get an SM7B that has a hum-cancelling coil in it - but even they can pickup some hum.