The line check. It's one of those things that most sound guys know they should do, or at least would like to have time to do, but often fail to get around to actually doing. Getting a line check done before the band arrives has saved me on several occasions. Not getting it done has cost us time (and when I say us, I mean the tech team, the band, the producer and everyone else in the room). So what is a line check? Just like it sounds, it's a time to check each line from the stage to the soundboard (and back, if you have wired monitors). There are many ways to do it, and I'll outline a few here. What's really important is that you check each line, from it's beginning--be that a mic, a DI or instrument cable--to the end, the soundboard. You're checking not only that signal is passing correctly, but that each line is appearing where you expect it to on the board. In larger systems, or for those with digital consoles, this is important.
Line checks are always easiest when performed with 2 people (with one über-geeky exception, noted below). When we finish our setup each week, normally either I or our FOH engineer will go the board, while the other stands on stage. We will typically work from one side of the stage to the other, checking everything in our path. For us that means we start with the drums. I'll get down on my hands and knees (hey, I didn't say doing a line check was glamorous...) and I'll shout into the kick mic. Then I'll shout into the snare mic, the bottom snare mic, the hat mic, etc. I say shout intentionally because we have gates on all our drum mics. Simply talking often won't pass a signal, and it's tough to see if they're working or not.
Normally, I'll say the name of the mic I'm shouting into to double check that we're dealing with the same mic. We don't often patch the snare mic into the kick channel, but it's happened, especially with new guys. So while I'm yelling, "KICK, KICK, KICK," the engineer is cuing the kick channel and hearing my voice. All is well. Testing vocal mics is easier, normally I'll just say (in a normal voice), "worship leader, worship leader."
Testing DI lines can be a bit tricky, and we often short-cut it. Because DIs rarely go bad (though I did throw a bad one away 2 weeks ago...), we normally just check the line. I'll unplug one of the vocal mics and plug it into the mic line coming out of the DI. It's good to make sure you plug the cable back into the DI when you're done. If you want to be extra thorough, you could pick up something like a Whirlwind Q-box or a Behringer cable tester that has a built-in tone generator. You can then plug your 1/4" cable into the output of the tester and generate some tone. That tests not only the cable, but the DI as well.
So that's the easy way to do it with 2 people. If you're the only one around, you can do it yourself. Resist the temptation to open up all the channels at once, put them in the house and check the mics. You'll find out if you have signal, but you won't necessarily know where it's going. If you have a really simple setup, you can get away with this, but throw in a snake, a sub-snake, some cross-patching and you can quickly find yourself chasing a fox through a cornfield. Plus, think of all the exercise you'll get running back and forth between FOH and the stage to check each line. Or you can do them in groups of 2 or 3, then at least you'll be close.
Now for the super-geek way to do it. I used this method last weekend--I was mixing, and I was also TD'ing--which meant I had no one around to help line check. Since our FOH position is up in the balcony, I didn't relish running to the back and upstairs, then back down 18 times to check all the lines. Call me lazy. So I got my geek on. To make this work, you'll need a few things: First, you'll need a digital console you can control from a computer; a Yamaha M7 works well. Second, you'll need said computer, a laptop, really as a desktop defeats the time savings, and the software to control said console. You'll also need a wireless connection for your console. Finally, you'll need something along the lines of a Rat Sniffer (mentioned in this post).
To put this in play, unplug each line from it's mic, plug in the Sniffer and use your laptop to turn on phantom power for that channel. If it's normally on, turn it off. The sniffer picks up on phantom power and will tell you if you have a cable fault. When you turn on phantom, the lights will light up and you know you're in business. Plug the line back into the mic, and move on to the next one. Work your way to the end, and you've done a line check without making a sound (make sure you set phantom back to the correct state for each channel when you're done). Now sure, you could use the laptop to turn on each channel and shout into the mics, but where's the geek cred in that? Using this method, I had the whole stage checked in just a few minutes, all by myself, without making a sound and without breaking a sweat. As my daughter would say, "Geek Squad..."
Now get out there, and check those lines...