The Modern Recording Chain

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Before audio is committed to your recorder, the signal must take a journey through the 'recording chain'!

Despite advances in digital technology, the recording chain has not changed much throughout the last few decades. However equipment has become more affordable and now the average home audio-engineer has a lot of options, including hardware that is used before the signal is recorded. This AudioCourses article will give an overview of the contemporary recording chain.

Microphone: The microphone is the link in the recording chain that converts sound energy into a small electrical signal. There are 2 main types of microphone, Dynamic and Capacitor/Condenser. Capacitor microphones require 'phantom power' which is often provided by a mixing console, channel strip and some audio interfaces. Capacitor mics also respond to higher frequencies better than their dynamic counterparts.

The majority of microphones terminate with a 3-pin XLR connector which is connected to the microphone input on a mixing desk/channel strip/audio interface. The 3-pin XLR protocol allows the use of 'balanced' lines which offer less noise (through the use of common mode rejection) and allow greater cable lengths to be used. When possible balanced connections should be used over unbalanced connections for these reasons.

DI Box: A DI box is used to convert a signal from one level and impedance to another. For instance a bass guitar will not sound at its best if it is plugged straight into the line input of a console. However, a DI Box matches the impedance and level and allows you to bring the signal into the desk/channel strip/audio interface, usually as a mic level signal on a XLR and/or a line level signal on a 1/4" jack, with minimum degradation of sound quality.

DI boxes can be 'passive' or 'active' - the active variety require 'phantom power' which is often supplied by the mixing console or by batteries. You can read more about DI Boxes here.

Preamp: The preamp will usually be found in the mixing console or separate channel strip. The job of the preamp is to bring the signal up to a level whereby you can work with the best signal to noise ratio possible without incurring any distortion. Typically microphones will require more amplification than line level signals such as synthesizers.

The quality of the preamp can also have a large impact on the quality of the sound reaching your recorder. Many cheaper desks have poor sounding preamps or preamps with insufficient gain. In recent years stand-alone 'channel strips' (sometimes called 'recording channel') are popular for people without good preamps in their console. Hardware units from the likes of SPL and Focusrite include good quality mic preamps as well as common processors such as EQ, Compression, Gating and De-Essing.

Processing: The inclusion of processing in the recording chain is a contentious one. Although from a purists point of view it is preferable to record with no processing of any form, many people do record with processing applied, especially when recording to a digital medium.

Processing includes EQ, Compression, Gating, De-Essing, Expansion and Limiting. In the recording chain the most common used processors are compression/limiting and EQ. Compression/limiting is often used on the way to a digital recorder/DAW to prevent any accidental signal peaks which would otherwise cause distortion. Any processing that is applied however can not be undone, so processing on the way in to the recorder must be carefully applied.

A-D Conversion: The conversion from an analog electrical signal to a digital binary signal is usually the last link in the contemporary recording chain. The converters are usually on the audio interface although the conversion process can also take place on digital desks and channel strips with digital output options such as S/PDIF, ADAT and AES/EBU.

Like the preamp, the A-D converters are an often overlooked part of the recording chain. Although the symptoms of poor A-D conversion can be subtle, there is a definite degradation in the sound quality. Usually poor A-D conversion is caused by inaccurate digital clocks causing 'jitter noise'. The effects this can have on audio include a 'blurred' stereo image and unwanted noise. These deficiencies cannot be rectified once in the digital domain so it is preferable to ensure that your A-D conversion is as accurate as possible.