Using a passive direct box to kill ground loop noise?

Glowbug · 17th March 2008, 05:06 PM

This was recommended to me by a friend who's into hi-fi as well as pro audio.

I'm getting a ground loop, using unbalanced connections, using cheater plugs "fixes" it but I know that's no permanent solution. Would a passive direct box solve the issue? If so, which ones are good? I see ones by ART, ProCo, and others...is this a "get what you pay for" kind of thing, or is one pretty much like all the rest? Since all the audio's going through this one box, it better not impart anything of its own or take away anything

http://www.partsexpress.com/webpage....ctGroup_ID=683

leadbelly · 17th March 2008, 05:23 PM

You need to say what your application is. A DI box is built for a specific range of input and output impedances. Are you trying to mate an instrument to an amp?

Speedskater · 17th March 2008, 09:21 PM

I just read that the Radio Shack, Audio Ground Loop Eliminator is surprisingly good! Especially when you consider the budget price.

Glowbug · 17th March 2008, 09:42 PM

Quote:

Originally posted by leadbelly
You need to say what your application is. A DI box is built for a specific range of input and output impedances. Are you trying to mate an instrument to an amp?

Nope, this is going between my preamp and my power amps...

cerrem · 17th March 2008, 09:54 PM

For audio you really need the best....and that is Jensen..
The reason is because you need the exceptional bandwidth with exceptional balance.... There is only one choice...

http://www.jensen-transformers.com/

cerrem

leadbelly · 17th March 2008, 10:20 PM

Quote:

Originally posted by Glowbug
Nope, this is going between my preamp and my power amps...

Then stay away from a DI box. The transformer inside them is wound for very different impedances and signal levels than found in line level home audio gear.

Although a little dated, have a look here: http://www.diyaudio.com/forums/showt...789#post408789

Glowbug · 18th March 2008, 12:13 AM

So what's the solution for breaking a ground loop like this?

hotbottle · 18th March 2008, 12:16 AM

You need an isolator, usually made from a pair of good quality 1:1 transformers. I see Speedskater earlier in the thread mentioned one.

Glowbug · 18th March 2008, 12:25 AM

Eek. $177 for that Jensen one pre-built.

Wonder if there's a cheaper solution...

imix500 · 18th March 2008, 01:03 AM

We use the Sescom IL-19 on Broadway for that purpose. I have run one on our AP rig and they really are ruler flat. Excellent transformer for about $50.

17th March 2008, 05:06 PM	#1
Glowbug diyAudio Member Join Date: Feb 2006 Location: Hillsborough, NC/McLean, VA	Using a passive direct box to kill ground loop noise? This was recommended to me by a friend who's into hi-fi as well as pro audio. I'm getting a ground loop, using unbalanced connections, using cheater plugs "fixes" it but I know that's no permanent solution. Would a passive direct box solve the issue? If so, which ones are good? I see ones by ART, ProCo, and others...is this a "get what you pay for" kind of thing, or is one pretty much like all the rest? Since all the audio's going through this one box, it better not impart anything of its own or take away anything http://www.partsexpress.com/webpage....ctGroup_ID=683 __________________ Jim J.

17th March 2008, 05:23 PM	#2
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	You need to say what your application is. A DI box is built for a specific range of input and output impedances. Are you trying to mate an instrument to an amp? __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

17th March 2008, 09:21 PM	#3
Speedskater diyAudio Member Join Date: Sep 2002 Location: Lakewood, Ohio	I just read that the Radio Shack, Audio Ground Loop Eliminator is surprisingly good! Especially when you consider the budget price. __________________ Kevin

18th March 2008, 12:13 AM	#7
Glowbug diyAudio Member Join Date: Feb 2006 Location: Hillsborough, NC/McLean, VA	So what's the solution for breaking a ground loop like this? __________________ Jim J.

18th March 2008, 12:25 AM	#9
Glowbug diyAudio Member Join Date: Feb 2006 Location: Hillsborough, NC/McLean, VA	Eek. $177 for that Jensen one pre-built. Wonder if there's a cheaper solution... __________________ Jim J.

17th March 2008, 09:54 PM	#5
cerrem diyAudio Member Join Date: Jun 2005 Location: San Diego, CA	For audio you really need the best....and that is Jensen.. The reason is because you need the exceptional bandwidth with exceptional balance.... There is only one choice... http://www.jensen-transformers.com/ cerrem

18th March 2008, 12:16 AM	#8
hotbottle diyAudio Member Join Date: Mar 2008	You need an isolator, usually made from a pair of good quality 1:1 transformers. I see Speedskater earlier in the thread mentioned one.

18th March 2008, 01:03 AM	#10
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Nashville, TN	Isolation Transformers We use the Sescom IL-19 on Broadway for that purpose. I have run one on our AP rig and they really are ruler flat. Excellent transformer for about $50.

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