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[Geoff Doane]

... On the console end, every connector was wired incorrectly with pin 2 as ground !  There's your problem !

Sounds to me like an interface problem might be the culprit too.

Since the rack and console are both at FOH, can you just replace that link with a known good cable?  It's not clear whether the dbx 223 is the XLR or TRS version, but if it's TRS, that's another possibility for a wiring error.  I've wired thousands of XLRs over the years, and I still mix up pins 1 and 2 from time to time (forget if I was soldering a male or female connector).  I've learned to test everything before it leaves the bench.

BTW, the terms "hum", "buzz" and "ground loop" often get tossed around interchangeably.  Personally, I try to reserve "hum" for low frequency noise (60 Hz or a harmonic of 60), while "buzz" is higher frequency stuff that doesn't necessarily seem harmonically related to anything.  Maybe we should avoid using "ground loop" until we know that the cause of the hum/buzz was indeed a ground loop (which are increasingly rare because most gear is pin 1 compliant these days).

Words of wisdom from the old R/EP Forum: "Too many grounds, hum; not enough grounds, buzz"

GTD

[Bob Faulkner]

Sounds to me like an interface problem might be the culprit too.

Since the rack and console are both at FOH, can you just replace that link with a known good cable?  It's not clear whether the dbx 223 is the XLR or TRS version, but if it's TRS, that's another possibility for a wiring error.  I've wired thousands of XLRs over the years, and I still mix up pins 1 and 2 from time to time (forget if I was soldering a male or female connector).  I've learned to test everything before it leaves the bench.

BTW, the terms "hum", "buzz" and "ground loop" often get tossed around interchangeably.  Personally, I try to reserve "hum" for low frequency noise (60 Hz or a harmonic of 60), while "buzz" is higher frequency stuff that doesn't necessarily seem harmonically related to anything.  Maybe we should avoid using "ground loop" until we know that the cause of the hum/buzz was indeed a ground loop (which are increasingly rare because most gear is pin 1 compliant these days).

Words of wisdom from the old R/EP Forum: "Too many grounds, hum; not enough grounds, buzz"

GTD

They are using the TRS version of the xover (the silver colored front plate version).  Thinking about it, they may be using the same type of "3-wire w/ground" (not sure what the proper term is for that type of XLR) cables, but in the TRS version (if that's even possible).  These cables run from the xover to the respective amplifiers.  Also, they may be running similar cables from the snake returns to the xover (XLR one end, TRS the other).  I'm only speculating these cables may be the same type "3-wire w/ground" because they are all pastel colors, which was like the one sacrificed for the ground-lift.  All their other cables are black (not that color matters, but I'm thinking they may have ordered a bunch of cables - not knowing what they were ordering...?)

There's a slight hum (60hz), but perhaps more of a buzz; it sort of depends on which cable was removed or inserted and where it was removed and/or inserted for testing (sorry for the ambiguity).

In the many years I've setup/troubleshoot/mixed sound systems, I rarely (maybe 3 times) have come across one of those cables that has a "4th wire" bonded to the cable assembly.  Pardon the ignorance, but why are some cables made with this 4th wire?  Pin #1 appears to function as designed, and pins #2 and #3 appear to function well together, why was another "ground?" introduced?



 

[Kevin Graf]

a]  Thinking about it, they may be using the same type of "3-wire w/ground" (not sure what the proper term is for that type of XLR) cables,
An XLR balanced analog interconnect cable should be a Shielded Twisted Pair (STP) or maybe a unshielded Cat5 cable.  There is no ground in a XLR cable, but there is a shield which may or may not be connected at the receive end.

b] Build a John Windt "Hummer Tester" (everyone should have one). Test at the amps inputs then again at the far end of the cable.

[Mike Caldwell]

Interesting you brought this up.  The cable I asked for from them (to sacrifice for a ground-lift cable) had pin 1 connected to the shell (factory constructed).  They mentioned they had several of those cables in their inventory (I'm not sure where, how, or if they are using any of those in their current setup).  It's possible they are using them.

You need to check for that at every connector, I have found the cheap import cables many people buy have the XLR shell tied to pin 1.

I need to build a tester to test for that!

[Bob Faulkner]

You need to check for that at every connector, I have found the cheap import cables many people buy have the XLR shell tied to pin 1.

I need to build a tester to test for that!

They did say the cables they purchased were very cheap.

[Mike Caldwell]

They did say the cables they purchased were very cheap.

You may just found a system wide problem.

You said they had this problem since the opening day, did they self install the system or hire it done?

[Tim McCulloch]

They did say the cables they purchased were very cheap.

Of course they're cheap.  Most churches by the cheapest shit they can find and call it "stewardship".

[Tim McCulloch]

You may just found a system wide problem.

You said they had this problem since the opening day, did they self install the system or hire it done?

My guess is that EVERYTHING in this facility was done by congregational volunteer "experts."

[Bob Faulkner]

My guess is that EVERYTHING in this facility was done by congregational volunteer "experts."

From my understanding, most everything was donated to them from another smaller church; since that time, some things (mostly wireless mics/IEM) were added afterwards.

[Tim McCulloch]

From my understanding, most everything was donated to them from another smaller church; since that time, some things (mostly wireless mics/IEM) were added afterwards.

That's a long time tradition of establishing or aiding new congregations.  Some give money, others equipment and supplies and some send workers - or a combination thereof.  All are gifts to be stewarded but sometimes that means not using a gift in the manner the giver anticipated.

It's the "Experts" (note the quotes and capitalization) that usually worry me in situations like this worship space, Bob.  Not that anyone would negligently or deliberately do a bad job but that in a remodel of grocery store to church, absent a gut and rebuild, there's plenty of ways to create compromises in the grounding and neutral bonding integrity as the work is done.

The bonded XLR shell is old-skool broadcast shielding where the entire grounding system has been designed to keep the Big RF Box out of everything audio near by.  I've never seen it routinely used in portable audio but have found that bonding wire in lots of "direct from China" mic cords.  Clip the bonding wire between Pin 1 and the bonding tab.  Done.  You've now spayed and/or neutered this potential problem (and Bob Barker will thank you. )

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