Microphones
A gain stage is at any point in your system where the signal passes through an amplifier. It is the process of optimising your input signal levels in order to maximise signal strength while minimising noise. Bad gain staging will result in high levels of noise and distortion as well as a decrease in the peak headroom.
Unbalanced Cables
An unbalanced cable consists of a signal and a ground wire. The ground wire surrounds the signal wire acts to deflect interference from external sources. However it also acts as an antenna and picks up some noise. Unbalanced cables tend to be used for Guitar amps as the maximum length for reduced noise is between 4-6 metres.
Balanced Cables
Balanced cables contain two signal cables that carry the audio. Both signal wires carry an identical audio signal with one of the signals inverted. If any unwanted electrical interference enters these signal conductors it will interact with both centre conductors equally. At the receiving end of the chain, the second signal is flipped. These equal voltages effectively cancel each other out because the balanced input is looking for difference between the positive and negative line. Any noise entering the cable will will be common to both conductors and will be rejected. This is know as Common Mode Rejection.
When recording a sound, you need to think about the reverb. This is when the sound bounces off objects and/or walls around it. It’s most noticeable when the sound source stops but the reflections continue for a split second. The reverb time is the interval between the first arrival of the wave and the last audible reflected wave.
“Reverb time is defined as the time it takes the reverb to go down in volume by 60 dB, or to 1 millionth of the original volume.” The abbreviation of this is RT60.
The two main types of microphone include Pressure Operated and Pressure Gradient.
Pressure Operated
Pressure operated microphones are designed so that only one side of their diaphragm is open to varying pressure. The back side of the diaphragm is closed off although there are tiny holes so that the pressure inside the container matches the outside pressure. This is not affected by changes in pressure caused by sound waves. As only one side of the diaphragm is exposed, pressure operated microphones only allow omnidirectional (circular) polar patterns.The small tie-clip microphones used in TV work are usually omnidirectional types.
Pressure Gradient
Pressure-gradient microphones are much more complex than pressure microphones since they have both sides of their diaphragms open to sound pressure variations. The diaphragm is exposed to the atmosphere and is sensitive to pressure changes caused by sound waves. This polar pattern resembles a figure eight.
Combining both pressure operated and gradient microphones allows you to explore different polar patterns. The most popular polar pattern is the Cardioid. It is a combination of both pressure operated and pressure gradient components.
All other polar patterns can be derived through some combination of the pressure operated and pressure gradient patterns.
References
Aviom Blog. (2016). What’s the Difference Between Balanced and Unbalanced?. [online] Available at: http://www.aviom.com/blog/balanced-vs-unbalanced/ [Accessed 23 Oct. 2019].
inSync. (2016). Gain Staging Like a Pro | Sweetwater. [online] Available at: https://www.sweetwater.com/insync/gain-staging/ [Accessed 23 Oct. 2019].
Ips.org.uk. (2015). Microphone Principles – IPS. [online] Available at: https://ips.org.uk/encyclopedia/microphone-principles/ [Accessed 26 Oct. 2015].
La Cerra, S. (2018). Everything You Need to Know About Gain Staging. [online] Hub.yamaha.com. Available at: https://hub.yamaha.com/gain-staging/ [Accessed 23 Oct. 2019].
Maliniak, D. (2014). About Common-Mode Rejection. [online] Electronic Design. Available at: https://www.electronicdesign.com/technologies/test-measurement/article/21799661/about-commonmode-rejection [Accessed 25 Oct. 2019].
Mynewmicrophone.com. (2017). Pressure Microphones Vs. Pressure-Gradient Microphones | My New Microphone. [online] Available at: https://mynewmicrophone.com/pressure-microphones-vs-pressure-gradient-microphones/ [Accessed 26 Oct. 2019].
Renaud, M. (2017). Audio Cables - Balanced vs Unbalanced. [online] Epiphan Video. Available at: https://www.epiphan.com/blog/audio-cables-balanced-vs-unbalanced/ [Accessed 25 Oct. 2019].
Shure.eu. (2010). Polar Patterns. [online] Available at: https://www.shure.eu/musicians/discover/educational/polar-patterns [Accessed 26 Oct. 2019].
Sweetwater. (1998). RT60. [online] Available at: https://www.sweetwater.com/insync/rt60/ [Accessed 25 Oct. 2019].