Gig Tip: Setting up the Basic Audio Channel
Working sound for a show, and still aren’t even sure on the basics? It is your first mainstage production? Or perhaps a buddy has wrangled you into doing sound for their band at a party, and you have *some* experience, but are still not clear on why things are done a certain way? Well, the easiest way to get a grip on microphones is to start with the basic Signal Chain. Follow a basic signal chain map, and rarely will you have a problem getting the sound you want!
Getting sound out of the console to the mains the way you want it is pretty simple as well, but there is a particular way you want to do it. Some engineers have different ways, but the basics of “Signal Flow” are the same. Here’s a quick and easy way on how we do it here. Now, you won’t find discussion about preamps, time-base processors or matrix management here. You need to know the basics about how sound works in a signal flow to make use of any other advanced processing.
What is the “Signal Chain”?
The signal chain is the path a signal travels from the source (such as a mic) through the audio system and out the speakers or on to disk for recording. A signal flow chart can be as lengthy as several pages in 9 point type, single spaced on front to back pages! But, the usual key to great sound is to keep the signal chain simple, and only add stuff when you MUST! The more you add, the more “noise”, or permanent alteration to the original sound, you create. Once you alter a signal, it is VERY difficult if not impossible to restore it 100%. So, to start with a simple, clean patch is always ideal. EVERY engineer starts with this basic signal flow chart. From the bedroom producer to Dave Rat, the basics don’t change:
Source (Singer/instrument) -> Transducer (microphone, DI, D/A interface, etc) -> Input transformer-> Preamp-> Gain -> Primary Send-> Equalization -> Channel Fader -> Secondary Send -> Master Fader-> Output Transformer
Now, that may seem a bit confusing at first, but let’s walk through a basic channel setup and you can start to see where these bits come into play. In setting up a basic channel, you won’t have to bother with input or output transformer since 99% of the consoles on the market don’t require you to do anything with that. But, as you gain more education and experience you will soon start to consider what *types* of preamps and transformers are in the consoles you are using when determining what tools to use for what gig.
But, let’s start with the basics that everyone needs to know:
**ALWAYS MAKE SURE THE CHANNEL IS “MUTED”. MAKE SURE THERE IS A RED LIGHT ON NEXT TO THE MUTE BUTTON ON EVERY CHANNEL JUST ABOVE THE SLIDER. IF IT IS NOT MUTED, DO SO NOW!**
-Select a microphone to use. Once you have the stand placed, run a cable to the “Snake”. Select what number channel you want to use by plugging the male end of the cable into the snake. Remember the number that you plugged your mic into! This will be important later.
**A Snake is a box much like a power strip, but it has points, or “channels” where you can plug in microphones and speakers. But, instead of electrical power to run appliances, it deals in sound signal. They consist of lines going INTO the board, like microphones and instruments) signals and lines coming OUT of the board for speakers or recorders. **
-Once your cable is plugged in, THEN plug in your microphone or instrument using the female end. Once you have your mic or instrument plugged in to the sanke, THEN attach the mic to the cable with the mic on the stand.
-After you have the mic hooked into the system, head to the sound console and let’s get that signal through the board into the speakers!
1) Press the “Solo” button (Located just above the fader, next to the mute button) to see the level of the microphone on the meter (located on the far upper right on a Mackie 24.4.4 for example, or in the center of the Yamaha MC32/12)
Have the artist or another tech go to the microphone to sound check the microphone. Just have them speak or sing at the level they will do so during a performance. NEVER Blow into or Tap on the mic!!!! This can damage the diaphragm and the coils within the mic and can cause feedback and power surges into the sound system. This is a bad thing.
2) Then, we *slowly* turn the Gain knob (the very first rotary knob at the top of the channel strip) to the right. This controls the amount of raw signal we are getting from the microphone to the console. As you turn up the signal while someone is singing or playing into the microphone, you will see the level on the meter increase. You want to keep the maximum level just within the “Green” section. This gives you a lot of signal to work with, but it keeps it from “clipping”, or distorting the sound. If it goes into the Yellow or the Red, you are clipping and need to turn the gain down.
3) Then, you want to select where you want that signal to go. We can send a signal to either the “Main Mix” (sometimes labeled as “L/R” mix) or to a number of “Aux Sends”. You will find the Aux Send knobs just below the Gain/trim knob and just above the Equalizer section on the channel strip. Simply turn those knobs to the right until the desired level is reached. Aux Sends simply send sound from the console DIRECTLY to another source, such as a monitor speaker or lobby speakers.
4) After that, now we can set the Main Output. This is the slider on the far right that controls the actual volume of the main speakers. Bring this one up to “U” as well.
What does “U” mean? It stands for “Unity”, or the point where an audio signal can pass through a board unaffected. It is neither being attenuated (Being turned down in volume) or amplified (being boosted artificially in volume). You always want to work as close to unity as possible to provide the cleanest sound with as little unneeded extra circuitry between the source and the final destination: The ears of the listener.
Now we have a full, uninterrupted signal going through the board!!! Now let’s make some sound happen!
1) Un-mute the channel by pushing the Mute button on the channel you are working with. The red light next to the mute button should go off. This means you are ready to send signal to that channel.
Once you have your gain level set, turn up the fader at the bottom of the channel to send signal to the main speakers.
You can now use the equalizer, or “EQ” to set your Highs, Mids and Lows. Just like an Equalizer on your home or car stereo, this allows you to make certain frequencies louder or softer in a particular signal. For example, you may want to have more “mids”, or the group of notes that are above 120Hz (or just below C3) on an upright bass, so you would turn up the lower two knobs until you reach a desired sound. At the same time you may want to bring out certain parts of sound that cause trouble. Such as someone who has a low bass voice may cause “pop” and distortion when talking into a mic. You can avoid this by turning down the low end knobs until the pop and distortion goes away.
If you need a signal louder (if you set the gain properly) you can now just bring the slider up without worry about the sound quality changing. If you don’t need that particular mic during a show, all you need to do is bring that slider down to bring it out. If you don’t want to hear ANYTHING from that mic, just hit the Mute button above the slider of whatever channel you don’t want to hear. That blocks out that mic entirely from sending signal to the board (just don’t forget that mute button when you actually need it)
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