Most every audio mixer has at least one set of level meters, similar to the one shown at the left. It shows the level of the audio leaving the mixer (going to a recorder or PA system). Many will also have “clip” or “overload” or “peak” lights at key inputs (shown on the right).
These meters aren’t just an entertaining display to look at. They are a very important part of your mixer’s operation and setup. Going through the steps is not difficult. But if you don’t set up the mixer correctly, you may have noisy audio, and other problems.
Let me explain…
The “clip” indicators are usually seen on MIC inputs. The typical setup procedure is to adjust the input gain trim control (near the mic connector) while speaking into the mic. When the “clip” indicator lights, reduce the gain setting just a bit, until the “clip” no longer lights. (A dynamic mic may not clip even with the gain at maximum. This is not unusual… dynamic mics need a lot of gain.) Now the gain on that channel is properly set for that mic. Repeat for all mics. Once set, the gain trimmer control will not need to be re-adjusted while the same mic is connected.
The input level must be correct for each mixer channel. The MIC channels have individual gain controls. The LINE LEVEL channels may have a switch to select between high and low levels. But most depend on the source device — CD player, etc — to have its own output level control.
Have another look at the LEVEL controls at the bottom of the mixer. Each one has a “default” position (or UNITY GAIN), usually marked with a line or some graphic to indicate the favored position. Depending on the manufacturer, the unity gain position may be 1/2 to 3/4 of the travel of the control.
When all of the input levels have been properly set, mixing becomes much simpler.
Try it… set all the LEVEL controls at their unity gain spot. (Do the same for the mixer’s MAIN OUT level control.) Then speak into the mics one at a time, and play audio from the other devices. The mixer’s main output meters should show activity lighting up all of the green, and bouncing up into the yellow. (This is the time to make adjustments to the output controls of the LINE LEVEL devices.) Now, simply starting with the level controls at their UNITY setting will give a reasonable mix. Only minor adjustments may be needed depending on the audio sources. (You may need to adjust the MAIN OUT level up or down a bit to get the ideal meter activity. That’s OK… you’ll only do it once.)
What is shown on the meter is what is being sent to your recording device, through the USB connection (if available), and to remote callers that may be connected via hybrid or codec.
A quick glance at the meters every now and then will let you know that everything is running along smoothly.
Many users will turn the knobs just enough to hear something in their headphones, and call it “good enough”. But that level is usually too low to even show up on the meters. Noisy recordings and poor interaction with 2-way conversations (phone or codec) will result.
Light those lights! (except the red ones) Crank it up!