Getting sound into and out of a mixer is really important. It's easy to make mistakes here. The first place to start is the microphone channels. Attach your microphones to the microphone channels on the board. If your microphones are condenser microphones that require phantom power, and your mixer supports it, flip the switch on the top or side of the unit that supplies phantom power. Now your microphones will be powered up and ready to go. Next, connect your line-level interfaces, such as your keyboards and line outputs from amplifiers and direct boxes.

Setting Recording-Friendly Levels

For each channel you record through the mixer, you need to set the level of each input. Activate the solo button on the channel you are working on to isolate the sound. For microphones, set the input trim control so the microphone's loudest sounds do not clip the input. If your mixer has a meter that lights up (most do), make sure the loudest sound stays in the green lights and doesn't hit the red. Repeat this step for each microphone you have.

Line-level instruments connect to the line channels. On the keyboard or guitar amplifier, you should adjust the gain on the amplifier, not on the recorder. The fader for those tracks should be set to “unity gain,” which means nothing added, nothing subtracted. Unity gain is marked with a zero. This allows you room in either direction for volume changes later on. Also, check the level meter to make sure you aren't clipping. Taking time like this will ensure that you don't clip and distort the inputs while you're recording.

Measuring Electrical Voltage

“Decibel” is a confusing term. Scientifically, the decibel is not a concrete measure of any one thing; it's a ratio of power or intensity to other factors.

There are actually a bunch of different decibels that we deal with. The basic decibel measures sound pressure. This measures the loudness of the sound pressure created. For instance, the sound of a plane taking off is about 120dB.

On a mixer, decibels are used in a much different way. The first way is as a measure of electrical voltage; the second way is as a level of sound output. When you look at a mixer's slider, you will see that it's marked up and down with decibel marks, ranging from negative decibels to positive decibels. See FIGURE 10-5.

Negative decibels? This seems to go against what we know of decibels. If you're comparing a volume slider to sound pressure, you will be confused. Think of the volume slider simply as a way of boosting or lowering the prerecorded signal. Negative dB values mean you are reducing the level that's been recorded, and positive dB values mean that you are raising the recorded output.

So, to sum this up, as you mix, place all of your volume sliders at zero. At that setting the mixer is not artificially boosting or cutting anything. You hear the signal that you recorded from the instrument or microphone itself.

Output Scale

More decibel madness! When we discuss using faders to boost and cut input volume, we might naturally push the vocals +2dB above normal to make them louder. Here's where the other side of the decibel confusion erupts, because when it comes to final output, decibels are measured using an entirely different system. We're now faced with a system called dBFS (decibel full scale). Decibel full scale simply considers 0dB as the absolute loudest signal you can have. You cannot pass 0dBFS or clipping will occur, which many of you have experienced. Since decibels aren't a fixed ratio, dBFS calls 0 the loudest and works backward. When mixing or mastering music, especially in the digital world, you can never exceed 0dBFS, ever. If you do, you will distort and clip the signal.

Maximize Music; Minimize Noise

We've talked about setting levels high enough so that they are full and don't clip. The reason for this is that the louder the input signal, the less noise the signal will contain. Even if you are planning on using a soft track, record the input high. Turning the track down later will help cover up any noise in the signal. Volume faders on mixers or computers can boost only a few decibels up. They can, however, reduce signals to nothing. It's better to have too much signal and reduce it later than to have too little signal and try to overboost.

Interfacing with the Recording Device

How you interface with your recording device depends on how elaborate your mixer is. For users with a simple mixer, the mixer outputs to separate left and right channels. This means you have two tracks to send to the recorder and two separate signals to use: right and left channels. Using the pan controls on the input channels, you can send certain sounds to the right cable and certain sounds to the left cable. Using a mixer like this doesn't mean you lose total control of the sounds. By panning certain sounds all the way left or right, you force that signal into one of the two cables. Each of the output cables can go to a separate track on your recorder. If you have buses on your mixer, those buses will also have outputs, also stereo left and right. For every bus you have, there will be another two outputs to your recorder. A decent-quality four-bus mixer will give you a total of four extra channels of output to your recorder. If you pan correctly and set the bus assignments well, you can route tons of signals flexibly to your recorder. If you use a lot of microphones and your recorder doesn't support many microphone inputs, this might be a cost-effective way to go — it's cheaper than buying all those microphone preamps separately.