Audio Hardware

The audio recording path

Microphones and preamps

Microphone diagrams

Open up the Charm city studios microphone presentation.

Dynamic

One common type of dynamic microphone uses a diaphragm attached to a coil that is suspended near a magnet (see Figures 4.3a and 4.4). The coil consists of some fine wire wrapped in a cylindrical fashion. The diaphragm, coil, and magnet make up the microphone’s capsule. You can change the capsule in some microphones to achieve different frequency responses or pickup patterns.

The diaphragm acts like an eardrum, when it moves back and forth it generates an electrical signal that converts sound waves into electricity.

Dynamic microphones are inexpensive and best for live sound reinforcement, but can also be used to record guitar amps, drums and vocals.

Ribbon

Another, less common, form of dynamic microphone is the ribbon microphone, which consists of a thin piece of corrugated, conductive metal—the ribbon—placed between two magnets (see Figure 4.3b). When sound waves hit the ribbon, it moves within the magnetic field, creating a small electrical current in the ribbon.

Condenser microphones also use a diaphragm that vibrates back and forth when sound waves hit it. However, in this case, the diaphragm is metal-coated and suspended in proximity to another metal plate (see Figures 4.3c and 4.5).

Condenser microphones are used frequently in studio settings and for recording live performances. They are more sensitive than dynamic mics and tend to reproduce the total frequency range more fully, due in part to the fact that the moving element, the diaphragm, is lighter than the diaphragm-coil unit of a moving-coil dynamic mic. Many condenser mics are more delicate and more expensive than moving-coil dynamic mics, though there are a number of robust, inexpensive condenser microphones available now.

Microphone polar patterns

Link to slides

Preamps

Signal levels

Source: BlackGhostAudio

The electrical signals to and from these devices are transmitted at various signal levels and may require different cables and connectors to integrate them into the recording path. In addition, some sound sources output digital signals that can be connected to digital inputs on an audio interface or digital mixing board.

In general, microphones produce a small electrical signal that is sent out as a balanced signal down a cable that has XLR connectors (also called Canon connectors). This cable is then connected to a preamp.

Devices such as synthesizers, audio processing gear, and mic preamps output line level signals, which are higher than mic level signals. Line level signals can be plugged directly into the line level inputs of an audio interface or mixing board. Typically uses XLR or TRS connectors.

Another common electrical signal level is the instrument level, which is associated most often with the output level of a guitar or bass guitar. The output of a guitar or bass guitar is an unbalanced signal carried on a cable with 1⁄4-inch TS connectors (see Figure 4.12d). As noted above, unbalanced signals are more susceptible to interference than balanced signals, so the cables should be kept relatively short.

The output of a power amplifier that is sent to a passive speaker (see “Amplifiers and Speakers” on pages 69–70) is referred to as speaker level, and is higher than any of the other levels discussed in both voltage and power. Typically, speaker level signals don’t interact with the other signals in the recording chain—they are designed only to be sent to speakers—and plugging them into other equipment can cause damage. Speaker cables often use bare, relatively heavy gauge stranded wires that connect to screw terminals or clamps. Speaker wires may also use banana plug connectors (see Figure 4.12h).

Cable connector types

Mixers

Simple mixer

input jack/controls
Aux send knobs
Three-band equalizer
Pan knob
Mute button
Solo button
Gain knob/fader

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