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Old 25th April 2013, 05:24 PM   #1
paulfx is offline paulfx  United States
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Default Interconnect Ground Cable Ground Loops

I've bought some bulk Belden cable, got a deal on RCA cable ends, and before installing new single-end cables on my system, I've been reading up on avoiding ground loops, Whitlock, and others. Whitlock mentions bundling of signal cables - why not have shields connected on one side for all cables to a source, and then run a nice big ground/earth cable, the only one, between each chassis? Only one safety ground would then be run to the building power.
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Old 25th April 2013, 08:57 PM   #2
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A green 10 gauge cable that can flow enough current to trip the panel breaker?
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Old 25th April 2013, 11:16 PM   #3
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I am out of my comfort zone here and CBW but two things come to mind. First, chasis are often tied to the signal ground through a small resistor so you would need to tie to signal gound not the chasis. Secound, ground loops develop in the samll differences in impedence between the grounds so you would need to devise some form of star grounding.
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Old 26th April 2013, 06:13 AM   #4
paulfx is offline paulfx  United States
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Thanks for replying, jj - - On Rod Elliott's grounding/earthing page

Earthing (Grounding) Your Hi-Fi - Tricks and Techniques

figure 4 has a schematic for a high current safety loop breaker circuit that puts 10 ohms between the signal ground and the safety earth except if there is a fault. Installing these would be a project that would never be finished by me. I checked the schematic for one of my Adcom amps and there are a dozen chassis grounds. So, let's add the assumption that I've checked for those 5 ohm or 10 resistors between signal or zero voltage point and chassis ground, and that they have been bypassed if present.

1) Right now I have my gear plugged into 2 mains wall outlets, maybe a few ohms of impedance in the earth/ground between them, and of course it hums like it doesn't know the words. If I was reckless I could disconnect one of the ground pins to the wall outlet. Potentially, if there was a fault, 15 amps could burn through the cable shields on the way to the ground/earth. A big ground bus or a star, with all cable shields cut on one end, would cut this ground loop and allow a breaker to trip if the worst fault happened in a chassis box.

2) If all remains safe, I would place the severed end of each cable on, say, the far end from my control box. No current would flow through the shields, but through the fat green wire. The signal would be still shielded from environmental garbage. Elliot touches on this in the article referenced above while discussing switching noise: "It might be possible to reduce this noise by installing a heavy earth strap that joins each chassis."

What do you think? Are there any obvious pitfalls to cutting the shields and connecting a ground star, or should I say an earth strap?
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Old 26th April 2013, 10:34 AM   #5
Pano is offline Pano  United States
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Have a look at Dave Davenport's excellent article right here in diyAudio
Audio Component Grounding and Interconnection

What you want to do makes sense, you just need to be careful in the implementation.
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Old 26th April 2013, 07:59 PM   #6
paulfx is offline paulfx  United States
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Found it in Davenport, "Parallel Earth Conductor (PEC). A PEC is simply a heavy wire connecting the two chassis." Jim Brown calls it "local bonding."
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Old 28th April 2013, 03:46 PM   #7
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This is what Audio Precision does:
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File Type: png AP ground wire.png (74.0 KB, 415 views)
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Old 29th April 2013, 12:47 AM   #8
paulfx is offline paulfx  United States
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Hey, there it is!
http://www.ap.com/download/file/149
"Floating BNC connectors help prevent ground loops."
I'm looking at a 6 gauge very fine strand (3000) cable for normally sold for lighting and portable power. This would act as a massive ground bus going down my equipment cabinet and over to the video monitor and cable box. Some nice Monster-type spade lug leads would then go to the back of each chassis. Also I'd be ready if I ever have to jump-start a locomotive.

Last edited by paulfx; 29th April 2013 at 12:50 AM. Reason: separate run-on sentences
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Old 29th April 2013, 01:09 AM   #9
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Quote:
Originally Posted by paulfx View Post
\Also I'd be ready if I ever have to jump-start a locomotive.
LOL. 6 gauge is big wire. Should make a hell of a buss.
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Old 29th April 2013, 02:43 PM   #10
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While visiting Audio Precision, you might read:

Sound Advice: AP Knowledge Base
Recommended Test System Grounding


Question:
What kind of grounding is best to use between the various devices in my test system?

AP High Performance Audio Analyzer & Audio Test Instruments : Service & Support
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