Live Sound & Production

[gruven65]

A while back, I ordered four of this type of cable.  I got them from an eBay seller, used but in like new condition.  I hadn't used them before last weekend.



I had to turn the gain up on every channel I had them on (all vocals). They all needed about the same adjustment.  I never really thought much about possible differences in resistance or whatever might cause this.  Is this common with the switched cables or with certain brands of cables? 

EDIT:  There was no difference in the quality of sound or clarity of the mics.

[agedhorse]

Only a problem on improperly made cables, or those that have defects. Something is definately wrong with them.

[gruven65]

But would the defect be the same across all four cables? Seems odd. Is there a way to improperly wire the cables that would cause a perceived volume loss?

[samkokajko]

In my experience with the Shure switched cables I have the same issue. They tend to require much more gain then if you just take them out of the chain. Just an inherent quality of the switch for some reason I suppose. We swapped over to a box Whirlwind makes that is a push to talk system. It can't do latch on but works for our voice of god applications.

[gruven65]

I'm glad to hear someone else has experienced the same thing.  Like I said above, there was no change in fidelity at all.  My wife recorded video of a few songs, and everything sounded great.  

[Kazinator]

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gruven65 wrote:

EDIT:  There was no difference in the quality of sound or clarity of the mics.

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Maybe not on a superficial listen, but the fact is that you're cranking the preamp gains to compensate. That brings in more noise and THD. You are not getting the cleanest, strongest possible signal from the source that you should be getting.

Say, it seems to say Neutrik, at least on the male connector. Is the switched one also Neutrik? If so, I'd expect better, oops. Maybe it's counterfeit, or some of their made-in-China stuff.

Sounds like there is some nasty parastic resistance in there which is significant with respect to the input impedance of the console and the source impedance of the mic. I.e more than a few ohms.

Check the DC resistance of each of the cable's three conductors with a digital multimeter. Ideally, it should be close to zero, like a fraction of an ohm.

Also, are these cables substantially longer than cables that you're used to? What cable are you comparing it to, and what are the specs for both? Are there any markings on the cable, like indication of the wire gauge? Is there a brand name and model number printed on the cable itself (not the connectors)?

It could be that the connectors are fine, but the cable is very resistive. That would also be consistent between different cables of the same length (whereas a flaky on-off switch would likely vary between units).

[gruven65]

I never said I had to "crank" the gains.  The preamps were still below 50% of their possible adjustment.  I just noticed what I consider a big adjustment (like from 9:30 to 11:00).

I'll check the resistance as soon as I'm able.  I have a multimeter, but I had only checked continuity with a cable tester. 

The cables are 25 feet long. The other cables were possibly 20 feet, but I'm not sure.  5 feet +- shouldn't be a significant difference though.

[agedhorse]

There is something wrong with all 4 cables. It has nothing to do with "parasitic resistance" (would actually be leakage) as that would be many orders of magnitude different.

If somebody does not understand how to wire a cable like this properly, then yes it's likely that they wired all of the cables wrong.

I have bulit up a number of these cables for clients and there are zero losses in  the on position and roughly >60dB of attenuation in the off position. This is not rocket science.

[gruven65]

agedhorse,

can you give me an example of improper wiring of these Neutrik switched ends that might cause the condition I posted about?  I have searched and only found a pdf on the Neutrik site that shows the connectors being as straight forward as any other XLR connector.  If I can repair these cables, I'd like to.  It's bound to save me a bit of money.  I'm sure I can handle the repair.

[agedhorse]

They are totally straight forward.

Reversing pin 1 & 2 is one way to cause problems, likely the most common IME.

[gruven65]

They should typically be pin 1 ground.  So you're suggesting if pin 1 and pin 2 are swapped, this could lead to the issue I'm seeng?  I just want to be sure.

[WynnD]

My bet is that they all have the signal ground jumped to the shield too. That would result in about a 6 db drop and a potential increase in noise. There is some possibility that this won't occur with every mixer, but will occur with better mixers. (MixWiz and better.)

[gruven65]

Would the noise be similar to 60 cycle hum or would it be more like a hiss?

EDIT:  Also, what would be the reason for bridging pin 1 and pin 3 on a XLR cable?  

[fdew]

My bet is that they all have the signal ground jumped to the shield too. That would result in about a 6 db drop and a potential increase in noise. There is some possibility that this won't occur with every mixer, but will occur with better mixers. (MixWiz and better.)

I don't know what you mean here.  Are you writing about connecting Pin 1 to the connector shell?  It is a bad practice but I don't see how it would cause a 6dB drop.

Pin 1 to shield to pin1  no connection to shell

Pin 2 to one half of the twisted pair to pin 2

Pin 3 to the other half of the twisted pair to Pin 3

[RoadRanger]

Probably wired at one or both ends like #2 here:

[agedhorse]

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WynnD wrote:
My bet is that they all have the signal ground jumped to the shield too. That would result in about a 6 db drop and a potential increase in noise. There is some possibility that this won't occur with every mixer, but will occur with better mixers. (MixWiz and better.)

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Not true, signal ground and shell shield are not part of the difference equation.

[gruven65]

Thank you for straightening that out for me. 

[gruven65]

Update:
I'm going to look a little dumb here, but I'll say it anyway.  The "problem" with the cables wasn't a problem at all.  The mixer, traveling in it's case in the trailer, somehow turns the gain knobs down as it rides down the road.  I have to say the foam on the inside of the case touches the first three or four gain knobs (that just happen to be the vocal channels).  When I swapped out the cables, it was the first time I noticed a volume difference.  I thought the cables were causing a volume drop, when it was actually the gain being turned down on the channels.  

I know...  But I run sound from the stage and I didn't have the ability to get out into the room at first.  Most of the clubs we play don't allow for a sound check, so I've had to build the mix as we go.  

There we have it.  Thanks again for ll the great suggestions. 

[agedhorse]

Good to know.

[wesg]

Hee hee. It's always important to check from first principles. I have to admit, magically moving knobs would not have crossed my mind.

I used to be a computer tech in another life, the first thing I would ask customers to do in a no-start situation was to verify that it was plugged in. You'd be surprised how often they weren't.