Mono vs Stereo Vinyl and how audio channels are used

Mono vs Stereo Vinyl
and how audio channels are used

Image by Lena Kudryavtseva

What do stereo and mono mean and what are audio channels? Audio channels are a source for sound. A speaker is a channel, a microphone is a channel, two speakers are two audio channels. In the simplest terms, each single-point source of sound is a channel.

When audio is recorded, it can be recorded on multiple channels. This is where terms like mono and stereo come in. Mono is recorded in one channel and stereo in multiple channels.

Stereo records
Stereo sound systems can be divided into two forms: the first is true or natural stereo in which a live sound is captured, with any natural reverberation present, by an array of microphones. The signal is then reproduced over multiple channel to recreate the live sound.

The Second is artificial or pan stereo, in which a single-channel sound is reproduced over multiple channels. By varying the relative amplitude of the signal sent to each channel, an artificial direction can be suggested. By combining multiple panned mono signals together, a complete, yet entirely artificial, sound field can be created.

In technical usage, true stereo means sound recording and sound reproduction that uses stereographic projection to encode the relative positions of objects and events recorded.

Mono records
Monaural or monophonic or mono sound reproduction is sound intended to be heard as if it were emanating from one position. This contrasts with stereo, which uses two separate audio channels to reproduce sound from two microphones on the right and left side, which is reproduced with two separate channels to give a sense of the direction of sound sources. In mono, only one channel is necessary, but, when played through multiple channels, identical signals are fed to each channel, resulting in the perception of one-channel sound imaging. In the mastering stage, particularly in the days of mono records, the one- or two-track mono master tape was then transferred to a one-track lathe used to produce a master disc intended to be used in the pressing of a monophonic record. Today, however, monaural recordings are usually mastered to be played on stereo and multi-track formats, yet retain their center-panned mono soundstage characteristics.

Mono sound can sometimes simply refer to a merged pair of stereo channels. Over time some devices have used mono sound amplification circuitry with two or more speakers since it can cut the cost of the hardware.




Stereo encoding on vinyl
A stereophonic phonograph provides two channels of audio, one left and one right. This is achieved by adding another vertical dimension of movement to the needle in addition to the horizontal one. As a result, the needle now moves not only left and right, but also up and down. But since those two dimensions do not have the same sensitivity to vibration, the difference needs to be evened out by having each channel take half its information from each direction by turning the channels 45 degrees from horizontal.

As a result of the 45-degree turn, it can be demonstrated that out of the new horizontal and vertical directions, one would represent the sum of the two channels, and the other representing the difference. Record makers decide to pick the directions such that the traditional horizontal direction codes for the sum. As a result, an ordinary mono disk will be decoded correctly as no difference between channels, and would play a stereophonic record without too much loss of information.

For additional sources visit:
Vinyl 101: How to Prepare Your Audio for Vinyl
Stereophonic sound From Wikipedia
Monaural From Wikipedia

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