ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3   Go Down

Author Topic: Grounding line level shields to rack  (Read 1574 times)

duane massey

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1005
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.
Logged
Duane Massey
Technician, musician, stubborn old guy
Houston, Texas

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3743
  • Atlanta GA
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.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

duane massey

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1005
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......
Logged
Duane Massey
Technician, musician, stubborn old guy
Houston, Texas

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3743
  • Atlanta GA
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.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

duane massey

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1005
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.
Logged
Duane Massey
Technician, musician, stubborn old guy
Houston, Texas

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 13152
  • Hickory, Mississippi, USA
    • Resotune
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
Logged
Tune it or don't play it... please

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3743
  • Atlanta GA
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.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Steve M Smith

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1137
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.
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 13152
  • Hickory, Mississippi, USA
    • Resotune
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

 
Logged
Tune it or don't play it... please

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3522
  • Audio Plumber
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
Logged
Pages: 1 [2] 3   Go Up
 


Page created in 0.137 seconds with 24 queries.