Microphone wiring 1

[LeeMcCauslin]

Any ideas on wiring up a boardroom with a PA?
We just bought 7 Shure 392c table top mics and a Peavy mixer and an amp. Got a couple of nifty ceiling tile mounted speakers. Drilled holes in floors and up walls and all kinds of stuff to make it pretty. Got it all hooked up and everything seemed to be working but 2 of the 7 mics start giving horrendous static the second they are plugged into the mixer. (Plugs are 5 pin deals that we had to make - came with the mixer - mic wires were not terminated until we screwed them into the plugs)(I am sure there is a name for them but I do not know it). I find it hard to believe we got two bad mics out of 7 so I figure we did something wrong but as far as I can tell, we did those 2 just like the other 5 and the system works beautifully without those 2 plugged in. We have re-terminated several times and I am about to take the original mic cable out of the mic and rewire from there but I just wanted to make sure there might not be something obvious that I am missing - everything I know about these mics I have learned in the last 2 days setting this up, reading the manuals that came with the equipment. Which ain't much.

I also imagine I don't have anything tuned and tweaked anywhere nearly as good as it could be but I was able to get voice out of the loudspeakers without feedback so I'll stand there until I figure out these 2 problem children. It looks like the mics are made to be re-wired because I can open the cover and unscrew the 5 wires to replace the cable with my own.

 

[Dexman]

Try connecting a known good microphone & cable into one of the suspect jacks and see what happens. Also take a "bad" microphone & cable and connect it to a known good jack.

If the problem follows the jack, then the mixer is the guilty party. If the problem follows the microphone & cable, try swapping out each component to see which one clears the problem.

 

[jeffmoss26]

Hmm, I can't find any information about those mics. Not sure why it would be a 5 pin connector. Mics are almost always 3 pin XLR.

jeff moss

 

[Dexman]

Hey Jeff! It's a 392-C surface mount microphone (sits on a stage or table-top). I think they have a 5-pin connector to mate with the microphone body, but have a standard 3-pin on the other end.

 

[LeeMcCauslin]

Did the swapping thing - problem follows mic.
The 2 extra wires control the LED on the mic I think - the instructions even say I don't have to use those if I don't want to. The mic cables came attached to the mic on one end and bare wire on the other end and we screw those leads into these 5 pin plugs that go into the mixer.

I think I must have a short in the mic wire - I noticed on another mic where we accidentally cut through an extension cable and while it was still live, if we touched those bare ends at the cut we got the same static sound. We replaced that cable and that one was good again.

The mic cover comes off and the cable is terminated to screw down connectors for easy swapping so I'm going to go ahead and put new cable in and see if that does it. BUt I am still kind of surprised if it's 2 bad cables from the manufacturer...

Thanks for letting me talk it through!

 

[Dexman]

Post your findings!

 

[LeeMcCauslin]

Well - I have achieved failure. I made a short run with completely new cable from the mic to the mixer - and it still gives nothing but static noise over the speakers. I can only assume now that it's a bad mic. At any rate, we need 2 more anyway so we'll order two more plus get these two replaced and see if we still get the problem. The mic cable we used is the cable suggested by Shure so I figure it must be OK. That still doesn't rule out my incompetence but I did do 5 good ones to the 2 bad ones...

 

[Dexman]

If the problem follows the microphone and not the cable or the input, then it does sound like there are 2 bad microphones.

I once purchased (3) AT&T 992 telephones once and all 3 developed problems with the LCD backlighting.

 

[LeeMcCauslin]

I think those two may have come from the Monday batch. We'll ask for Wednesday mics this time. ;-)

 

[Dexman]

Friday batches are suspect too!

 

[jeffmoss26]

From looking at the specs, it only looks like 2 conductors and a shield. Not sure what these 5 pin connectors are...

jeff moss

 

[LeeMcCauslin]

This is the mixer
Peavy 8 automix - the 5 pin connectors came with the mixer and the mics have 5 leads in them.

 

[Dexman]

The extra leads could be power. I'm not too familiar with that model microphone so this is going to be a wild guess. Is there an outboard power supply or some device that is supposed to be placed between the microphone and the mixer?

 

[LeeMcCauslin]

No - I just screw the leads into the 5 pin modules and plug them right into the back of the mixer. THe extra leads control a "live" LED (it's on when there's power and the mic is live)that can be turned off by pushing a pressure sensitive plate on the front of the mic to mute it - actually there are dip switches inside the mic to control what the plate does - push to talk, push to mute or disable the plate. But I don't think that has anything to do with it (the static problem) - other than that is 2 extra wires that could be shorted somewhere. The system works fine with the 5 good mics.

 

[Dexman]

Once the replacement microphones are connected and tested, please post the results!

 

[AndyD5]

All speakers and Mics function on the same princapal one black one red. Some speakers like the ones for your drop ceiling tiles have different color leads for different Ohms resistance and or amperage of sound device. I've seen stage mics with the five wire ends two are the basic function of the mic the toggle switch should complete the connections of the black or negative lead sometimes there is no color to indicate polarity. the adittional leads are usually about 12 volts DC for a light source on the mic to show status such as on/recording/live and the extra leads can also be power for a wireless device that needs power the local theater I've worked with here has a 24 volt floor reciever for the wireless mics that they attach to the end of the instruments in the orchestra pit etc two of the leads are that power the third is the light on the device to show it is functional it also indicates wether it is in recording/ or live mode by additional LEDs again I wish we had pictures on here. so many things make more sence to me when I see it. as for your static issue try putting shrink tube and quick connect eyelits so that as little wire is exposed as possible because static is just noise from ingress in most cases it could also be a treble/bass adjustment.

One last thing to check the mic head the material could be rubbing in such a way it causes static charge and that can make noise.

Good luck hope you get it working

I have some $75.00 Karaoke Machine mics and I bought four new mics last week for my machine at the dollar store for 99 cents each and they WORK BETTER.

Andy the Cable Guy Chandler, AZ

 

[LeeMcCauslin]

If I hadn't already boxed them up and sent them back, I would take a picture and put it on here - This site can show pictures from the web (I'd upload to imageshack and link to it here). But the new mics should be here any day now.

Thanks for the thoughts though - I'll keep them in mind when hooking up the new mics.

 

[LeeMcCauslin]

Just a note to complete this thread - The two replacement mics came in and I installed them where the other 2 had been and no major problems so far. I still feel like a professional audio tech could tweak this system better but we have 7 mics around a boardroom and folks can talk and folks can hear and there is no horrible feedback or static interference so I figure not bad for a first time. I don't get to write the checks so I can't get a guy in here who really knows what he's doing but hopefully, if there are any more problems, they will.

Thank you all for your help and suggestions!

 

[Dexman]

Glad to read that everything worked out!