Originally published in the April 2002 issue of DRUM! Magazine
A mixer is designed to combine (or mix) acoustic and electronic audio signals captured by microphones. Along with mixing the signals together, mixers have features that are designed to adjust the relative volume of each signal, adjust the tonal quality of the signal, and place the sound within a certain physical space. Mixers also have the capability to route any or all of the signals to other audio gear for additional processing.
Most mixers can easily be divided into three main components: the input section, the channel strips, and the output section. The inputs are often located directly above the channel strips, and the output section is usually located on the right side of the mixer.
The Input Section
The input section of a mixer serves two functions: it routes microphone and instrument outputs into the mixer and adjusts the signal to its optimum strength. Depending on how your mixer is designed, it may include several different styles of inputs. Microphone inputs are most often female XLR-style jacks. Instrument signals enter the mixer by way of standard 1/4” jacks. The input section of your mixer may also include inputs for a tape recorder (often RCA-style jacks), and inputs that are labeled as auxiliary inputs or auxiliary returns. (We’ll go into more detail about aux inputs later).
In order for the mixer to do the best possible job, it’s critical for the inputs to be adjusted properly. The signal from a microphone is pretty weak in comparison to the signal from an electronic drum kit or a sampler. Microphone inputs are much more sensitive than line-level inputs, and plugging a microphone into a mixer passes the signal through a preamp that boosts its strength. Since some signals may be stronger or weaker than others, most mixers also have a “trim” adjustment that is used to fine-tune the strength of the signal for optimum performance. Once the microphone or instrument signal has entered the mixer it is routed to a particular channel of the mixer.
The Channel Strip
The channel strip can be further reduced to its components. On most mixers, there will be three main sections: auxiliary sends, equalization and pan, and level controls.
In just about every mixer, aux send controls are rotary knobs that grab a portion of the signal from that input and send it in another direction. In most cases, the signal is sent to auxiliary outputs that are then connected to some type of outboard processor like a reverb, echo, or multi-effects unit for modification. The outputs of the processor are then connected back into the mixer through the auxiliary inputs. These inputs have a control that determines how much of this return signal is allowed to come back into the mixer. Depending on the flexibility of your mixer, you may have one, two, or several separate sends and return inputs. It’s also common that the aux send outputs are monophonic while the aux returns are stereo. If you don’t use any type of outboard processor, you can use the aux returns as another set of stereo inputs. While they aren’t as flexible as channel inputs, they will often come in handy.