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Old 2nd July 2013, 09:52 AM   #41
AndrewT is offline AndrewT  Scotland
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sort the problem.
Don't put on a sticking plaster.

I think it is Whitlock that has published a hum detector circuit for detecting the PIN1 problem. I would think (not being a PA roadie) that every PA person will have the hum detector in his/her pocket.
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Old 2nd July 2013, 11:24 PM   #42
Enzo is online now Enzo  United States
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I'll say this and move on.

If you are faced with a stack of gear to set up as a system, and encounter a ground loop. Will you tear apart the equipment and reconfigure the grounding therein? Or will you use a ground lift externally? The OP was about a patch panel after all, which implies concerning one's self with connecting gear together.

As a professional touring sound man, I did indeed carry all manner of tools to detect problems. But it is not sufficient to detect problems, you also need to be able to correct them in the field. SO I also must carry a bunch of things like ground lift cables, as well as phase reversal adaptors, various balanced line pads to tame hot signals, and adaptors to convert most any connector to most any other. I can't tell the band "Gee, this gear isn't made right, sorry about the hum." I have to provide good clean sound free of hum.
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Old 3rd July 2013, 08:40 AM   #43
AndrewT is offline AndrewT  Scotland
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Yes, and having detected the piece of defective gear you then use your spare balanced cable that is clearly marked "cap coupled screen" on one end. Conventional Chassis coupled screen at the other end.

As far as I know that is the "normal solution for the PIN1 problem. There are probably others.

But if one is building a bit of kit then one does not build in a PIN1 problem, one builds it right.
To me post1 sounds like he is building a patch bay. He won't need to incorporate a ground lift switch if he uses Chassis connected screens.
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Old 13th July 2013, 03:37 AM   #44
Jsixis is offline Jsixis  United States
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I like enzo have to have every connection possible because the average musician doesn't have a clue and many older amps have polarity switches so polarity is always a problem.
That said, everyone should read this which I consider the most accurate way to wire things.

Sound System Interconnection
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Old 19th October 2013, 05:35 PM   #45
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Jsixis View Post
That said, everyone should read this which I consider the most accurate way to wire things.

Sound System Interconnection
cool

btw, instead of swith, and/or wire internally, I made this simple 'XLR-jumper' to create the single ended connection

any problems doing so ?
is it ok, or should I better mount that switch

I doubt I will ever run it balanced
but you never know
should I ever go buy a parametric EQ, I guess it probably better be a balanced
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Old 20th October 2013, 08:30 AM   #46
AndrewT is offline AndrewT  Scotland
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Tin,
Pin1 should be connected to Chassis.
Pin3 (Cold) should be connected to -IN (for Receiver), or -OUT (for Source)
It is not wise to short these two together.
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Old 20th October 2013, 02:08 PM   #47
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by AndrewT View Post
Tin,
Pin1 should be connected to Chassis.
Pin3 (Cold) should be connected to -IN (for Receiver)
I expect they are, internally

Quote:
Originally Posted by AndrewT View Post
It is not wise to short these two together.
why not ?
(it is input on a classD power amp)

is it not normal procedure connecting balanced negative to ground on input, when doing single ended to balanced preamp signal ?

mind you, I cannot connect a balanced signal when the jumper is in
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Old 20th October 2013, 06:19 PM   #48
AndrewT is offline AndrewT  Scotland
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Audio ground is not chassis.
Balanced uses chassis for pin1, or it should.

The cold (pin3) if used as an audio ground is NOT chassis.

If you want to connect an unbalanced impedance Source to your balanced impeddance Receiver then the cable should be balanced to reject/attenuate interference on the cable.
The Source gets the conversion where audio ground gets connected to screen (pin1) and to Pin3 to feed along on wire to the receiver's pin3
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Old 20th October 2013, 07:02 PM   #49
tinitus is offline tinitus  Europe
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... the cable should be balanced to reject/attenuate interference on the cable.
ah, interference
don't know how much that worries me

sounds like you try to say pseudo balanced cable
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Old 20th October 2013, 07:04 PM   #50
AndrewT is offline AndrewT  Scotland
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Is that what Rane and Jensen tell us, when they suggest a converter cable? Keep the balanced for as much as possible. That must include the cable attached to the balanced impedance Receiver.
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