Wednesday, July 4, 2012

What's All The Noise?

At work the last few weeks there have been numerous complaints coming from a couple of the smaller rooms around the church, that there was a ton of noise on the playback channels. I had the intern at my disposal one day last week and we went on a grand tour of the remote venues.

The first was the room where they do kids' church. I ran into the youth pastor who said that he had found something patched wrong in the video tower, but even with the DVD player behaving itself there was still a lot of buzz on the channel. 
To start out I flipped on the power to the system and pushed the playback fader up to unity. Sure enough, Buzz Lightyear... in the house. Something stopped me right there though. The intern pointed out that the faders never got that high. So I said for him to set it where they usually ran things. He set the fader at -40. (!) A quick twist to chop 40 dB of gain out of the trim knob, shove the fader back up to unity and things were clean and quiet. Playback came out at the level they wanted with 10 dB to go before the fader topped out.

Room One... done. On to the chapel.

I had a similar complaint in that room but this time the operators were blaming the combination of the laptop used for projections and the projector itself. They had tried everything at their disposal, from using direct boxes with ground lifts to using ground lifts on the power to the equipment. (BTW don't do that, it's not safe or indeed legal. But that's another post.) The situation turned out to be similar though. With the faders at unity I reduced the gain on the trim pots until the levels were about what were expected. Then we found a few other things that needed attention.

Monitor one had been having some quality issues which we traced to the graphic EQ stashed in the amp closet back stage. Every fader at -12 was probably not what the manufacturer intended. We shoved them all up to zero and I sat on stage with a mic and a radio until the intern had knocked the few offending frequencies down.

Moving on, we had also been asked to try and move the choir mics so they picked up better. We crawled up into the attic to see if there was any slack in the wires and there wasn't. But I spied the interface boxes and wondered when the last time the batteries were replaced. (Some hanging mics have a box where the tiny connector plugs in and you get a regular sized XLR to run cable back to your console. Many of them have a battery slot so you can use them with consoles that don't have phantom power.) There were no batteries in them but they turned out to be getting phantom just fine so we didn't worry about it.

Checking the console to make sure that phantom was on though, revealed yet another knob problem. Ever see a channel EQ with all the knobs twisted to eight o'clock? We did. Straightening them out and removing a couple offending frequencies had the choir mics picking up a lot better without physically adjusting them.

So there you have it Brethren of the Knob and Fader. When a problem crops up, especially in an installed environment where consoles aren't zeroed out every day, it always pays to take a look at the board before you set off on a long and fruitless quest in the wiring.

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