Wired Guitar + Wired Microphone = Electric Shock

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A Tech Tip from Shure Applications Engineering:  

The musician was bewildered…more than usual. "When my guitar is connected to my amp with a cable, and I sing into a wired mic, I get an electrical shock through my lips. If my guitar is wireless, it does not happen. If my mic is wireless, it does not happen. Why do I get shocked when the guitar and the mic both use a cable?"

Of course, the mic gets blamed because it touches the lips. But the culprit is not the mic, nor the cables. The culprit is the guitar amp.

Because of the electric design of many vintage guitar amps, it is not uncommon for a small amount of current (120 VAC) to "leak" onto the amp chassis.

Read more: Wired Guitar + Wired Microphone = Electric Shock


Wireless Mic Antenna Placement - Closer Is Better

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A history lesson: when Shure introduced the Vagabond professional wireless mic system in 1953, its primary purpose was to replace the 20 foot cable attached to the microphone. The Vagabond was not expected to reliably transmit a signal for hundreds of feet. In the 1970s, wireless mics began to grow in popularity, particularly for in-studio TV production (think "person presenting the weather") and for Las Vegas stage shows. But even then, the transmission distance was relatively short.

As wireless mic technology improved, the transmission distances increased. Eventually, the pro audio world began to think of a wireless mic as replacing a 200 foot cable run, not just a 20 foot mic cable. So antennas were moved farther away from the stage - often ending up by the mixing console for the sake of convenience. This antenna relocation method worked well for three decades, primarily because there just were not many RF (Radio Frequency) signals in the air.

But now in 2013, the trend is beginning to reverse. The reason is the...

Read more: Wireless Mic Antenna Placement - Closer Is Better


Proper use of the Shure UA874US directional antenna

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Shure Apps Tech Tip: Correct use of the UA874US Directional Antenna

Recently, a local theatre group was staging a Broadway musical. During technical rehearsals, there were ongoing problems with the wireless microphone system and I was asked to consult with the production crew. As the theatre was near my home, I stopped by one afternoon.

There were ten channels of Shure UHF-R in L3 band, and twelve channels of UHF-R in the H4 band. All receivers were UR4D+ units, and were grouped in their respective frequency bands, i.e., all L3 units in one group and all H4 units in the other group. I was pleased to find that the operating frequencies had been properly coordinated. But then I saw the antenna set-up and immediately knew the source of the nagging problems.

Here is what I found:

Four UA874US antennas located 60 feet from the stage with direct line-of-sight to the stage;

Two antennas for the L3 receivers; two antennas for the H4 receivers;

All antennas mounted vertically;

All mounted side by side with six inches from antenna to antenna;

All four antenna BNC cables were less than 10 feet in length;

All antennas had gain settings of +12 dB;

One antenna had no LED illuminated.

Before I continue, test yourself. There are three major errors in the antenna setup. (Insert "Jeopardy Final Answer" theme music here.)

Time is up. Here are the errors:

Read more: Proper use of the Shure UA874US directional antenna


Antenna separation - or why does my wireless drop out?!

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A customer purchases a Shure PSM900 (Personal Stereo Monitor) system and installs the PSM transmitter in the equipment rack next to a Shure SLX wireless mic receiver. At the rear of the rack, the PSM transmit antenna is six inches away from the SLX receive antennas. When the PSM transmitter is operating, the SLX wireless system becomes unreliable, exhibiting numerous drop-outs. Power off the PSM transmitter and the SLX operates satisfactorily.

Now here is the rub: it is not a frequency issue. The frequencies were properly coordinated to avoid interference between the units. So what is the root cause? An analogy will explain.

Read more: Antenna separation - or why does my wireless drop out?!


How you know you've arrived.

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by Mike Sessler,

Sometimes younger TDs will ask me how we know when we're doing a good job. It's a legitimate question. As my friend Dennis Choy says, for us, excellent is normal. A weekend when everything goes right, and no one notices we're there is a weekend when we did our job. So if that's normal, how do we know we're doing a good job?

Well, certainly one could say that if we're having more weekends when everything goes well than we are weekends that don't, we're doing a good job. Or perhaps if we don't get comment cards that it's too loud. Or maybe if the pastor liked the lights or the sound. Those are not bad metrics; but let me suggest another one.

You're doing a good job if your team can pull off a major event when you're not there.

I had this experience a few weeks ago. In the days after NAMM, I came down with some type of contagion. I was completely laid out for about 6 days. Unfortunately, this coincided with a night of worship that we had on the books. I was scheduled to mix FOH, while my ATD Jon was to run ProPresenter. Lights and video were to be handled by volunteers.

And here I was, sacked out on the couch, unable to move. Once it became clear I wasn't going to be able to be there, we started putting out calls. One of our former Pro operators (who also happens to be my daughter) stepped up to run Pro so Jon could mix. Our communications guy offered to help set the stage.

When the event started, the team absolutely rocked it. It wasn't long after it ended that reports started coming in that it was incredible. It was then that I realized I was doing a good job. When I started receiving emails saying, "We missed you, but your team did great!" I knew. I no longer have to be there for things to go very well.

Now, Jon did tell me it was a lot of work and a bit stressful without me there, and he had a few questions for me about the console. But the fact that they ran the whole event without any of my direction or participation is a great indication that all the work we've done building reliable and easy to use systems, training teams and developing our culture is paying off.

I hated to miss the evening, and I missed mixing it; but I'm glad I did.


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