Home recording studio equipment explanations: Mixers

Mixers perform three functions. As the name implies, they mix the signals of many individual channels into a smaller number of channels (usually stereo or surround sound). They also allow the person being recorded to monitor the already recorded material on other tracks. Thirdly, they allow the signals to be mixed with and processed through effects processors. Digital mixers add the function of converting analog audio and live sounds to digital signals and vice versa.

• Automated faders = Different than scene memory, this function actually records all of your fader movements. It's as if you are recording the technical details of your mix on a separate track. This is a great function if you have a a lot of fader rides, and wish to record your mix in a way that you can re-create it at any time.
• Aux = The function of the mixer that allows you to mix each channel with studio effects. You send the channel to an external or internal effects processor and receive the modified signal back.
• Balanced input = The three pronged input for a balanced microphone cable. Low impedance microphones, which are of a higher quality, connect to a cable that leads to a three pronged connector.
• Buss = As the name implies, the transportation route for each channel's audio. Busses lead to the outputs of the mixer. By selecting which bus to send each channel 's recorded signal on, you select which mixer output that signal goes to.
• DA/AD conversion = Digital mixers must convert analog audio (and live sound) into digital signals. They reverse the process when outputting the final mix in an analog form.
• Effects returns = How much of the desired effects (reverberation, echoes, etc.) are sent back to affect the signal. You are basically mixing the levels of the original sound with the reverberations or other effects.
• Effects sends = How much of the signal is sense to the effects processor. If you wish to create the atmosphere of a very small echoey room, you send more of the signal.
• Equalization = The function that boosts or lowers different frequencies in the sound. You can change the timbre of a sound by boosting higher frequencies, for example.
• Fader grouping = The ability to connect a number of faders to move together. This is important if you have a group of instruments or singers that need to have their levels raised or lowered together, and you don't have enough fingers to do each separately.
• Gain knob = Since inputs may have widely varying levels of signal, the gain knob allows you to cut or boost that signal so that it is similar to the other channels. A basic technique is to line up all of the faders to the same level, and then, using the gain knob, to make sure that all of the signals are at about the same volume.
• Impedance = the resistance of the circuitry to the signal. Balanced signals encounter low impedance, while unbalanced ones encounter higher impedance.
• Monitoring = Each recording mixer must allow you to hear the already recorded tracks as you record new tracks. If you wish to play along with prerecorded material, you need to be able to hear that material without it being recorded on the tracks you are now creating.
• Optical connection = Optical digital signals use a special cable which is thinner than most cables. They have a unique interface as well. Adat signals can carry up to eight channels of audio on them.
• Panning = The ability to determine whether the sound is going to come from the right or left side in a stereo mix.
• Peaking = When a signal is too strong, it peaks. That means that it reaches the limits that the mixer circuitry can accurately handle and you get distortion. By turning down the gain knob or faders, you can prevent peaking.
• Phantom power = Condenser microphones require a power source in order to function. Most mixers can supply that power through this function.
• Post-fader = When the signal is processed after it is modified by the fader. Your vocalist may want to hear a precise mix of the music. Therefore, you would send them a post-fader mix, with the faders set up to give that precise mix.
• Pre-fader = When the signal is processed before it goes to the fader's control. For example, you may send a pre-fader mix to the monitor headphones. In a situation where the technician does not want to hear the other tracks, but the vocalist does need to hear them, you would use pre-fader monitoring. The technician turns down the faders so he doesn't hear it, but the vocalist does.
• RCA connection = Inputs and outputs to and from tape recorders and similar devices usually use this type of connection. Many digital inputs and outputs are also sent via RCA connection.
• Sampling rate = The amount of audio samples per second. Similar to a old-style film, and audio track consists of lots of little snapshots, called frames. The human ear perceives them as being one continuous track. The higher the sampling rate, the smoother and more realistic the audio. Additionally, since waves of audio get longer at lower frequencies, smaller sampling rates do not always captured the entire frequency range at that lower end. The higher the sampling rate, the fuller and deeper the audio becomes.
• Scene memory (snapshot) = The ability to remember all of the mixers settings at a specific time. If your song has various sections, and you want to preserve different settings for each section, this function is essential. At the post of a button you can return to your memorized snapshot.
• Signal to noise ratio = In any system there will be some background his or noise. The stronger the signal over the noise, the cleaner the audio will be. Mixers that have a high signal to noise ratio are better.
• Stereo inputs = Most tracks record only one channel of audio. Stereo inputs receives stereo signals from stereo devices. For example, you might have stereo sounds on your keyboard that you wish to preserve and don't want to use two mono tracks.
• Unbalanced input = An input for a quarter inch plug. These are the connections to high impedance microphones, instruments such as electric guitars, keyboards and other audio sources. They tend to transport a stronger signal from electronic sources.
• Word clock = the signal used to synchronize all of the digital devices in the system. If you are mixer is working at 44.1 kHz sampling rate and your digital recorder is that 48 kHz sampling rate, you will have problems. You must tell the mixer to transmit a word clock of 48 kHz.