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| - Compressors are objects in the Wario and Yoshi series.
- A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible, so the main action of a pump is to transport liquids.
- Go back to Main Page > Documentation > Mastering The first in a series of "Masterclass in Mastering with Angelus" ;-) If you think that you can contribute something about this subject, please edit this page and write. It does not matter the slight it is, surely that will be useful. And don't forget to put your name/nick in the Credits section, as well to stamp the version into the Page Version Section.
- A circuit which reduces the dynamic range of an input signal. A basic compressor circuit consists of an envelope follower and a VCA. The envelope follower produces a control voltage corresponding to the volume of the input signal, which is then controls the VCA which is controlling the gain of the output signal. Processing circuitry modifies the control signal such that, as the volume of the input exceeds a certain point, the control signal is attenuated, reducing the VCA's gain and hence reducing the volume of the output signal.
- The term "audio compression", meaning audio level compression is used in the sound recording and live sound reinforcement fields. In this context, it refers to a process whereby the dynamic range of an audio signal is reduced. A different, non-linear type of compressor is used to reduce the dynamic range of a signal for transmission, to be expanded afterwards. This reduces the effects of a channel with limited dynamic range. See Companding.
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| abstract
| - Compressors are objects in the Wario and Yoshi series.
- A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible, so the main action of a pump is to transport liquids.
- A circuit which reduces the dynamic range of an input signal. A basic compressor circuit consists of an envelope follower and a VCA. The envelope follower produces a control voltage corresponding to the volume of the input signal, which is then controls the VCA which is controlling the gain of the output signal. Processing circuitry modifies the control signal such that, as the volume of the input exceeds a certain point, the control signal is attenuated, reducing the VCA's gain and hence reducing the volume of the output signal. Typically the modification of the control signal is expressed as a "compression ratio". For instance, if the ratio is stated as 2:1, it means that when the input volume rises past a threshold (called the "knee"), the envelope follower's output is only allowed to rise half as much as the increase in the input volume, which causes the output volume to be reduced by that ratio. When the compression ratio is "infinite", it means that past the knee, as the input volume goes up the control voltage actually goes down, which means the output gets no louder no matter how much louder the input gets. This is referred to as "limiting", and a dedicated device that does this is called a limiter. Because compression tends to reduce the average level of the output signal, an additional feature called the "make-up gain" is provided for the output. This allows the output signal to be raised back up to the average level of the input signal. The effect is that the signal is as "loud" as it was before, but the dynamics are more under control. Extreme settings of compression and make-up gain are often used to increase the apparent sustain of instruments that are plucked or struck, notably guitars. Compressors may have many additional features. A lag processor for the control signal is sometimes provided so that the user can control abrupt changes in the VCA gain, which may be noticeable as artifacts in the output; typically an attack and release rate control is provided. Some compressors have a mechanism known as a "side chain", which allows a signal separate from the main input to be routed to the envelope follower, which will make the output track the dynamics of the side chain input. Compressors are often used to "fatten" bass signals, and may provide a noticeably different timbre vs. the uncompressed signal. This occurs because at low frequencies, the envelope follower has a tendency to follow the actual waveform instead of just the signal envelope, which in turn causes the VCA to distort the output signal in a characteristic manner.
- Go back to Main Page > Documentation > Mastering The first in a series of "Masterclass in Mastering with Angelus" ;-) If you think that you can contribute something about this subject, please edit this page and write. It does not matter the slight it is, surely that will be useful. And don't forget to put your name/nick in the Credits section, as well to stamp the version into the Page Version Section.
- The term "audio compression", meaning audio level compression is used in the sound recording and live sound reinforcement fields. In this context, it refers to a process whereby the dynamic range of an audio signal is reduced. An audio level compressor reduces the dynamic range of an audio signal by using a variable gain amplifier to reduce the gain of the signal if it passes a set threshold. The amount of gain reduction is usually determined by a ratio control. That is, with a ratio of 4:1, if the input level is 4 dB over the threshold, the gain will be reduced so that the output level will only be 1dB over the threshold. This is typically carried out in analog systems by using a voltage controlled amplifier which has its gain reduced as the power of the input signal increases. Compressors usually have controls to set how fast the compressor responds to changes in input level, known as attack, and how quickly the compressor returns to no gain reduction once the input level is below the threshold, known as release. The attack of a compressor is always set to at least as slow as the lowest frequency signal in the track, and usually a few times slower. Because the compressor is reducing the gain (or level) of the signal, the ability to add a fixed amount of gain at the output is provided so that an optimum level can be used. Compression is commonly used in television commercials to boost the perceived volume of the sound track. Television broadcasters have limits on the instantaneous peak volume of the audio track in a broadcast rather than its root mean square volume over the entire 30 second commercial segment. By applying compression followed by gain compensation the overall volume of the track is increased without increasing its peak volume and the sound is perceived as louder. Some compressors implement side-chaining. This feature uses the dynamic level of another input to control the compression level of the signal. This is used by disc jockeys to lower the music volume automatically when speaking, for example (known as ducking). Another use is in music production, to maintain a loud bass track, while still keeping the bass 'out of the way' of the bass drum when the drum hits. A different, non-linear type of compressor is used to reduce the dynamic range of a signal for transmission, to be expanded afterwards. This reduces the effects of a channel with limited dynamic range. See Companding.
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