Works everywhere but this one place

[johnbasalla]

I have to provide a little extra microphone audio for meetings. I always use the same old Sure microphone mixer and Radio Shack wireless microphone added to the large 10 mic audio system. All of a sudden, at this one location, neither one worked. Both units have worked at this location in the past. The only difference was this time the main audio system was set up behind stage-right instead of stage-left, so we were plugging into different AC sources. When I got it back to the office, I had to provide the same service, plugged into the same large audio system for a meeting there. So, I set the Sure and the mic up, initially as a test. Both units worked fine and I ran them for the entire 3 or so hour meeting. Any ideas about what might have occurred?

For the record, at the place where the units failed, I had a Telex wireless microphone delivered from the office along with a different Sure microphone mixer (An M-267) which has a meter on it as the other one doesn't. The M-267 and Telex worked fine.

 

[Chuck]

Have you checked to see if there is any relationship between the RS wireless and the Telex? Same frequency maybe? 10.7 MHz away?

Off hand, I'd suspect the Radio Shack wireless. In any congested RG environment, like almost any city, they are junk. Friends don't let friends use Radio Shack wireless mics.

 

[johnbasalla]

I had the Radio Shack microphone set up, and once it wasn't working, I pulled it out and put it away. The Telex came later. At no time was there an attempt to have them on simultaneously, although they are both on different frequencies and have worked together fine at other times. I usually only hear bad things about Radio Shack, and in some instances I agree. However this Radio Shack wireless microphone was purchased in 2001 and is still working fine (except for the one story above).

 

[Denny E.]

In some less expensive wireless circuitry, and really not limited to this, over time the transmitters or receivers frequency may drift a bit. This sometimes leads to more noise in the RF signal and also less range between the units. This could possibly be some of your problem. We had a Shure VHF system at the television studio where I worked that exhibited this problem. Although the receiver's location never changed and the RF microphones stayed within their established perimeters, more and more drop-outs were being noticed. The system just needed re-alignment.

Dennis

 

[Chuck]

I had the Radio Shack microphone set up, and once it wasn't working, I pulled it out and put it away. The Telex came later. At no time was there an attempt to have them on simultaneously, although they are both on different frequencies and have worked together fine at other times. I usually only hear bad things about Radio Shack, and in some instances I agree. However this Radio Shack wireless microphone was purchased in 2001 and is still working fine (except for the one story above).

Perhaps there is something else in the location that is on the same frequency as the Radio Shack mic. This happens a lot in hotels and other facilities with lots of meetings going on. Frequency coordination becomes a big issue in these situations.

 

[SirRoxalot]

The question is, what RF-generating equipment is located stage right that doesn't exist stage left? The Radio Shack probably doesn't have the same capacity to filter out spurious emissions that the Telex does. Dimmers, lighting controls, and transmitters for ADA listening systems will put out PLENTY of RF & harmonics that could interfere with a wireless mic system.

 

[johnbasalla]

R-F generating equipment vis-a-vis the wireless microphone may be a possibility, however all of the stuff that would generate that would be way up high on the other end of the auditorium in the booth. We weren't using the house system because it couldn't take the required number of microphones. It was strange that both the Sure mixer and the wireless microphone failed simultaneously. The units did power up, but that was it.

 

[Chuck]

Perhaps you had a bad (or intermittant cable).

 

[RealityCheckr]

OK, basic #1 - What was the problem, exactly, with plenty of detail? "It didn't work" won't cut it - you need to give us all the details.

My hunch is a cable issue, possibly a ground loop or use of an unbalanced cable. Was the same cable used in all cases? Was it balanced or unbalanced?

Good luck

 

[johnbasalla]

Sorry. I thought I was giving plenty of detail. We had these two units that didn't function. The wireless microphone was plugged into the Shure mixer which was plugged into the large 10 mic system. Then I tried plugging the wireless microphone directly into the 10 mic system, and it still didn't work. I plugged it into the same XLR that the Shure was plugged into. I know that the Shure wasn't working either because another wired mic was put into it, and we weren't getting anything out of that mic either. When the other Shure mixer arrived with the other wireless microphone, I can only say now that I'm pretty sure that I used the same cables to plug into the system because by that time we were in a mad rush to get everything up and running. There is a possibility that I may have grabbed other cables, although I don't remember doing that. I'm pretty sure about the cables because, being in a mad rush, I left them out waiting for the other pieces to come for a quick turn-around.

 

[grich]

... I know that the Shure wasn't working either because another wired mic was put into it, and we weren't getting anything out of that mic either...

Any chance the wired mic needed phantom power that the old Shure mixer couldn't provide? Been hosed by that before.

 

[SirRoxalot]

R-F generating equipment vis-a-vis the wireless microphone may be a possibility, however all of the stuff that would generate that would be way up high on the other end of the auditorium in the booth. We weren't using the house system because it couldn't take the required number of microphones. It was strange that both the Sure mixer and the wireless microphone failed simultaneously. The units did power up, but that was it.

The controls for all of that equipment are in the booth, but the dimmers and other actual high-power electrical circuits are in the stage area. You don't run high power to the booth. You run low power control circuits to the booth. And, believe me, large amounts of AC power generate all kinds of RF, and harmonics can put that RF in an unbelievably wide range of frequencies. Ditto the listening devices. Transmitters for that equipment are much more likely to be in the stage area, with antennae on the house side of the wall, in line of sight to ALL of the seats.

 

[johnbasalla]

SirRoxalot gives me something to think about. Thank you. I may go there to do some testing to determine if what you share may indeed at least be part of the problem. A couple of things...

1. The wired mic needed no phantom power. Those wired mics have been used many times successfully with this Shure mixer. The Radio Shack wireless was plugged in as has been done "a thousand times" before. The Telex wireless, once it arrived to save the day, was plugged into the same electrical outlet as the Radio Shack mic.

2. The focus of many of these responses has been the wireless microphone. The first Shure mixer also didn't function. It's a simple four mic input A/C plug-in mixer. Fortunately, the M-267 Shure mixer came to the rescue. The M-267 was plugged into the same electrical outlet as the other mixer that did not work.

 

[RealityCheckr]

OK....

1) what did not work? No audio, noise, something else?

2) Did you get meter readings on the Mixer?

3) Did you get audio in the mixers headphones?

 

[ChiefEngineer]

Leave the Radio Shack wireless out of the picture. It is not a constant. I have used them but they use common frequencies and therefore are more prone to interference.

Did the Shure mixer work after it failed or did it die forever? If it died forever the death of both may have been just coincidence. If it now works then look at cables.

The 267 only has a line output. Some mixers have mic or line out. Bypassing and placing any mic output into something needing line level input will result in nothing good.

As you were feeding one mixer into another mixer was there a tech in the booth for the big system? If everything still works (mixer) then look there if the same cables and proper levels were used. Many new installs have mixers in a room that is controlled either automatically or by a person. Turn the power off to the room and the whole thing goes away.

Will be interested in the results.

 

[johnbasalla]

1) what did not work? No audio. Not one peep of sound.
2) Did you get meter readings on the Mixer? There are no meters on the Shure mixer and there was no modulation on the main system the Shure was plugged into. In other words, the same answer as for question #1.

3) Did you get audio in the mixers headphones? No. The Shure does not have a headphone jack. The M-267, which came to the rescue and worked fine, does and of course worked well.

I had another meeting in another remote location to set up for and run this evening. I used the Shure mixer that failed at the other place and the Radio Shack wireless microphone, and everything worked fine this evening.

I understand the mic/line level dynamic, and that wasn't part of the problem.

Like tonight, and at the place where these two units didn't work, I plugged the Shure microphone mixer (mic level-XLR)) into a microphone input on the larger portable unit. There is always a tech with the larger unit which goes from place to place as needed. At the place where my two add-ons didn't work, there was nobody up with the house system because we weren't using it. I don't know if that system was left on or was off.