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Author Topic: Grounding line level shields to rack  (Read 13202 times)

duane massey

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Re: Grounding line level shields to rack
« Reply #10 on: April 09, 2014, 09:47:20 AM »

Ivan,  the venue had a portable console that was only used for certain events, and was disconnected when not in use. The system was still used for DJ's and background music/paging, so it was active at all times.
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Duane Massey
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Ivan Beaver

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Re: Grounding line level shields to rack
« Reply #11 on: April 09, 2014, 12:47:16 PM »

Ivan,  the venue had a portable console that was only used for certain events, and was disconnected when not in use. The system was still used for DJ's and background music/paging, so it was active at all times.
Then the unused inputs should be muted.
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Ivan Beaver
Danley Sound Labs

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duane massey

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Re: Grounding line level shields to rack
« Reply #12 on: April 10, 2014, 12:45:33 AM »

There was no way to mute the inputs. The rack was in an upstairs area that was inaccessible to the employees, and this was pre-digital era. We floated the ground on the output side and tied on the input side (at the rack) and the problem went away. Soundcraft board, Rane analog rack gear, the old days......
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Duane Massey
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Ivan Beaver

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Re: Grounding line level shields to rack
« Reply #13 on: April 10, 2014, 07:29:44 AM »

There was no way to mute the inputs. The rack was in an upstairs area that was inaccessible to the employees, and this was pre-digital era. We floated the ground on the output side and tied on the input side (at the rack) and the problem went away. Soundcraft board, Rane analog rack gear, the old days......
So what you are describing is a "non normal" situation.

When I was talking about how I do grounding-it was referring to normal situations.

Anything out of the "norm" often requires a different approach.

Also a lot of the analog gear "back in the day" had bad pin 1 problems.  Just to compound things.
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Ivan Beaver
Danley Sound Labs

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duane massey

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Re: Grounding line level shields to rack
« Reply #14 on: April 11, 2014, 10:22:06 AM »

I'm just grateful that a lot of the challenges we faced "in the day" are no longer an issue. I do kinda miss the look of awe on client's faces when you could walk in, clip one or two shields on a couple of cables, and make the "noise" vanish, although (in my life as an onsite service guy) I still find problems created by the previous "installer" that can be fixed this easily.
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Duane Massey
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John Roberts {JR}

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Re: Grounding line level shields to rack
« Reply #15 on: April 11, 2014, 11:09:28 AM »

The irony surrounding lifting shield grounds to reduce noise, is that every day the amount of RF we encounter increases. At some point you may have to re-connect that clipped shield to reduce RF interference.

JR
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Ivan Beaver

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Re: Grounding line level shields to rack
« Reply #16 on: April 11, 2014, 01:06:17 PM »

I'm just grateful that a lot of the challenges we faced "in the day" are no longer an issue. I do kinda miss the look of awe on client's faces when you could walk in, clip one or two shields on a couple of cables, and make the "noise" vanish, although (in my life as an onsite service guy) I still find problems created by the previous "installer" that can be fixed this easily.
I used to carry around clip leads for exactly that purpose-to make or change the grounding path of a particular piece of gear.

And many pieces of top of the line professional gear had XLRs-but was NOT balanced (on the outputs and some inputs).

Add to that all the gear that had pin 1 problems and you would spend most of the time setting up for a gig trying to get rid of noise.
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Ivan Beaver
Danley Sound Labs

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Steve M Smith

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Re: Grounding line level shields to rack
« Reply #17 on: April 11, 2014, 01:46:48 PM »

Add to that all the gear that had pin 1 problems and you would spend most of the time setting up for a gig trying to get rid of noise.

I keep reading about 'pin 1 problems' in old equipment.  What does that refer to?


Steve.
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John Roberts {JR}

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Re: Grounding line level shields to rack
« Reply #18 on: April 11, 2014, 02:14:01 PM »

I keep reading about 'pin 1 problems' in old equipment.  What does that refer to?


Steve.

Maybe you don't have google where you live?  8)

"Pin one problem" refers to balanced/differential (3 wire interface) gear, where noise current dumped into pin 1 (like from a shield ground, or ground loop) contaminates the audio on pins 2 and 3. In hindsight this seems obvious but many product designers struggled with this, decades ago, even moi.  :-[

JR

 
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Mac Kerr

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Re: Grounding line level shields to rack
« Reply #19 on: April 11, 2014, 03:35:41 PM »

Maybe you don't have google where you live?  8)

Google links, and to be more specific, Pin1Problem.com.

Mac
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Re: Grounding line level shields to rack
« Reply #19 on: April 11, 2014, 03:35:41 PM »


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