Analogue

When Thomas Edison invented the phonograph in 1877 the recording era was born. Analogue audio utilises the continuous variations in a physical quantity, typically an electrical voltage, to represent sound. Below is an outline of the key stages of producing an analogue audio recording;

1. Capturing Sound
The analogue audio recording process begins by a transducer in a microphone moving in correspondance to air pressure variations.

These variations are converted to low voltage electrical signals that are sent through a copper cable to a pre amp. The pre amp boosts the voltage to a stronger level that is suitable for further editing.

The signal may be mixed with other signals from different microphones or instruments on a mixing console. This allows for the adjustment of individual volumes and applying effects such as equalisation or reverb to create the final mix. The final mix is then sent to a recording device.

Typically a tape recorder, the signal of the final mix magnetises particles on a moving tape, creating a physical representation of the sound wave.

The final mix is further processed to ensure consistent sound quality across the entire recording. This may include adjusting overall volume, equalisation and compression. Different mastering mixes may be made for different formats such as vinyl, compact disc and radio.

For widespread distribution copies are created from the master recording. This could include creating vinyl records by pressing the master disc into heated vinyl, leaving an imprint of the grooves.

Each step introduces it’s own characteristics to the final recording, contributing to the overall sound quality and character.

Consumer Analogue Audio Formats

Listed in order of consensus of quality;

This format offers the highest fidelity due to; It uses magnetic tape wound on spools housed within a reel. Similar to cassette tapes, the tape is coated with a ferrous oxide layer and uses read/write heads to record and playback audio. Reel-to-reel tapes generally offer higher fidelity compared to cassettes due to their wider tape width and faster speed.

These consist of a flat disc made of polyvinyl chloride (PVC) with spiral grooves etched on one or both sides. A record player uses a stylus to read the grooves, which translates the physical variations into electrical signals that are then amplified and played through speakers. Vinyl records can achieve very high fidelity, especially high-quality pressings from well-maintained masters. However, they are more susceptible to factors like surface noise from scratches and dust and tracking errors from misalignment of the cartridge.

Designed primarily to be convenient and portable, this format uses a thin magnetic tape housed within a plastic cartridge. The tape is coated with a ferrous oxide layer that can be magnetized to store audio information. Cassette players use a read/write head to convert electrical signals into magnetic patterns on the tape and vice versa.

These cartridges contain a continuous loop of tape with four tracks on each side. Similar to cassette tapes, 8-track players use read/write heads to record and playback audio. This format was popular in the 1960s and 1970s, particularly for car audio, but has largely been superseded by cassettes and digital formats.

Digital

Digital audio represents sound using discrete values instead of the continuous variations used in analogue audio. These discrete values are known as samples and they can be thought of as functioning in the same way as how a series of frames form an animation. The number of samples played back or recorded per second is known as the Sample Rate and is usually measured in kHz (thousands of cycles per second) for high fidelity audio. Each sample is encoded into set lengths of binary code known as the Bit Depth which determines the resolution of each sample. Higher numbers of sample rates and bit depths allow for greater resolution and sound quality of digital recordings. Digital Audio allows for more versatility in the manipulation and storage of audio than analogue techniques.

The digital recording process captures sound by converting continuous sound waves into discrete digital data. Here's a breakdown of the typical steps:

1. Capturing Sound
Similar to analog recording, microphones convert sound waves into electrical signals. Sound and instruments can also be generated entirely in the digital domain.

The crucial step in digital recording is the ADC, which takes the analogue electrical signal from the microphone and samples it at a specific sampling rate. This means it measures the voltage of the signal at regular intervals (thousands of times per second for high-fidelity audio). Each sample is then quantized, meaning it's assigned a discrete numerical value based on its measured voltage within a specific range.

The resulting stream of digital data (binary code) representing the audio is then stored on a digital storage medium, such as a hard drive.

Digital audio editing software allows for non-destructive editing of the recording. This means you can manipulate the audio data without affecting the original recording itself. You can perform various edits like: Trimming: Removing unwanted sections. Splicing: Combining different sections. Applying effects: Adjusting volume, equalization, adding reverb, etc.

When playing back the recording, the digital data needs to be converted back into an analog signal that speakers can understand. This is done by a DAC, which translates the binary code back into a continuous electrical signal representing the original sound wave. The quality of the DAC plays a role in determining the fidelity of the playback experience.