Some very extensive audio knowledge. Introduction to general terms.

Impedance: specifically refers to resistance and resistance in "variable and capacitance. Frequency impedance characteristics (capacitance, capacitive reactance). However, since we usually talk about impedance value, it is only expressed in ohms, so people may mistakenly think, that impedance is simply "DC resistance". current". .

Coaxial line: two wires of coaxial line, one is in center and other is surrounded by a mesh structure around center line, and center line and grid line are separated by insulating materials. It got its name because central line is coaxial to reticular layer.

Optical fiber. An optical fiber is a fiber that transmits light.

Balanced Line: All signal lines must use two wires, one output and one input, that is, one is output signal path and other is signal loop. In common signal line, these two wires are divided into positive and negative, positive line is output path, and negative line is signal circuit separated from ground. In a balanced system, another signal line is used, which has three wires inside and connects to XLR terminals on outside. Among three internal wires, one is responsible for transmitting positive phase signal, other for transmitting negative phase signal, and third for ground.

RGB: Red Green Blue. These are red, green, and blue colors of "video," not red, green, and blue colors of print, photos, and objects. Also known as three primary colors (Primary), this means that colors that can be seen in all video systems consist of red, green and blue.

VGA: A computer monitor specification introduced by IBM in 1987 with a resolution of 640 x 480.

SACD: Super Audio CD. Literal translation of Super CD. It is a new music medium above CD, as well as a new format jointly launched by original inventors of CD, SONY and Philips, which uses DSD recording method.

DVD-Audio: DVD Audio is a new audio format that replaces CD with DVD Audio specification.

Compact Disc: A digital music disc jointly developed by Sony and Philips with a diameter of 12 cm and a diameter of 8 cm. The former is most common and can provide 74 minutes of high quality music.

DVD: A new generation of ultra high capacity discs that look like CDs. They will be widely used for recording high quality video and audio programs and as a storage device for computers.

Digital to Analog Converter: A device that converts digital audio signals to analog audio signals in digital audio devices (such as CDs, DVDs). The D/A converter can be turned into an independent machine for use with a CD player, and is now often referred to as a decoder.

CD player: a machine that separates mechanical part of CD player's transmission.

Oversampling: The sampling rate is several times higher than standard CD system sampling rate of 44.1kHz. Its purpose is to facilitate filtering of digital noise after digital-to-analogue conversion and to improve high-frequency phase distortion. CD player. Early CD players used 2x or 4x sampling, and more modern machines have gone up to 8x or higher.

HDCD: short for High Definition Compact Disc, is an encoding system that enhances sound quality of a CD, compatible with traditional CDs, but requires playback on an HDCD decoded CD player or an external device HDCD decoding for improved quality. Results.

Bit (bit): The smallest constituent unit of a binary digital signal that always assumes one of two states: 0 or 1.

Bitstream: A Philips technology that converts digital CD signals into analog music signals.

Dolby B, C, S: A series of tape noise reduction systems developed by Dolby Corporation in USA that are used to reduce "hiss" produced by tape recording and expand dynamic range. Type B noise reduction system can reduce noise by 10dB, Type C noise reduction system can increase up to 20dB, and Type S noise reduction system can reach 24dB.

Dolby Surround: Sound in which rear effects channel is encoded into a stereo channel. A decoder is needed to separate surround sound signal from encoded sound for playback.

Dolby Pro-Logic: Adds a front center channel to Dolby Surround to block movie dialogue on screen.

Dolby Digital (Dolby Digital): Also known as AC-3, this is next generation home theater surround sound system released by Dolby Laboratories. Its digitized audio includes 5-channel left front, center, right front, left surround, and right surround signals, all of which are independent full-range signals. In addition, there is a separate subwoofer effect channel, commonly known as 0.1 channel. All these aggregated channels are called 5.1 channels.

AV Power Amplifier: An amplifier specially designed for home theater use, usually has more than 4 channels and surround sound decoding function.

Dolby Digital Amplifier: Also known as AC-3 Amplifier, it is an AV power amplifier with Dolby Digital decoding function.

THX: A surround sound standard developed by Lucasfilm Corporation in USA that enhances Dolby Pro Logic surround sound system and further enhances surround sound effect. The THX standard contains a number of strict and specific requirements for playback equipment, such as audio and video sources, amplifiers, speakers, and even connecting wires. Products that comply with this standard and are certified by Lucas receive THX logo.

THX 5.1: THX based on Dolby Digital system.

DTS: Discrete Channel Digital Home Theater Sound System (Discrete Channel Digital Home Theater Sound System), which also uses independent 5.1 channels, effect is same or even better than Dolby Digital Surround, it is Dolby Digital . Surround Strong competitor.

SRS: A system manufactured by SRS Company in USA that uses two speakers to create surround sound effects.

Frequency divider: A circuit device in a speaker that is used to divide input music signal into different parts such as high, mid and low frequencies and then route them to appropriateproviding tweeters, mids and woofers for playback.

Biamping: A connection method in which each speaker of a speaker is driven by an independent amplifier channel. A pair of two-way speakers requires two stereo power amplifiers and two pairs of speaker cables. See Biwiring.

Two-wire connection: A connection method in which two sets of speaker wires are used to transmit high and low frequencies of music signal, respectively. Biwiring requires use of specially designed loudspeakers with two pairs of terminal blocks.

Bridge connection. This is a bridged amplifier that uses two identical stereo amplifiers after a cascade, and each amplifier converts left and right stereo to mono.

Amplifier: A collective term for preamplifiers and power amplifiers.

Power amplifier. This is an electronic device used to amplify signal strength to make a speaker produce sound. A power amplifier without auxiliary functions such as source selection and volume control is called post-cascade.

Pre-amplifier: The pre-amplifier and control part before power amplifier, which is used to expand signal voltage range, provide input signal selection, tone and volume control, and other functions. A preamplifier is also called a preamplifier.

Integrated Amplifier: An amplifier that combines two parts of pre-amplification and power amplification in one package.

Tube amplifier. Another name for a tube amplifier.

Telephone: This is an important device used to regenerate sound waves of vinyl records. The most common are moving magnet and moving coil cartridges.

Coaxial speaker. A coaxial speaker is a tweeter located in center of midbass or woofer. These two monomers are not full range monomers, but they each have their own crossover network. Its advantage is that there is no monomer placement time phase problem. The sound waves of two monomers reach listener's ears at same time, and audio and video are accurate and relaxed.

Horn Horn: This is a sounding compression driver plus a horn throat and finally a horn hole to form a complete horn.

Rated Power: For power amplifiers, rated power generally refers to effective value (RMS) of power that can be continuously delivered; this means that such a powerful power amplifier must be needed to drive speaker. dynamics is mainly determined by its sensitivity and impedance characteristics. It also does not mean that you cannot equip a power amplifier with an output power greater than rated power of speaker. Just like driving a car, drivingDriving a sports car at 300 kilometers per hour does not mean that a car accident will happen, you do not need to go that fast. Similarly, as long as volume is not increased blindly, high power amplifiers can also be equipped with low power speakers.

Peak Music Output Power (PMPO): The output power calculated from instantaneous peak voltage of music signal, its commercial value is greater than its practical effect. The power of PMPO can be 3-4 times higher than internationally recognized RMS rated output power (RMS). For example, RMS power per channel of first portable tape recorders is only 4 or 5 watts, but it is labeled PMPO, and value can be increased with one click .Approximately 20W.

Single-ended gain: The output stage of power amplifier consists of one amplifying element (or several elements, but connected in parallel as a group) to amplify two positive and negative half cycles of signal. Single-ended amplifiers can only work in class A conditions.

Push-pull amplification: The output stage of power amplifier has two "shoulders" (two sets of amplifying elements). When current in one "arm" increases, current in other "arm" decreases, and states of two switches in turn. For load, it appears that one "hand" is pushing and other "hand" is pulling, and they are jointly performing current output task. Although class A amplifiers can use push-pull amplification, it is more common to use push-pull amplification to form class B or AB amplifiers.

Class A: Also known as class A, during entire signal period (positive and negative two half-cycles of sine wave), any element of amplifier output power will not have current cutoff (i.e., stop output) of class amplifiers. Class A amplifiers get very hot and have low efficiency in operation, but have inherent advantage of no crossover distortion. All single-ended amps operate in class A mode, while push-pull amps can be class A, class B, or classes A and B.

Class B: Also known as class B, two positive and negative half-cycles of a sine wave signal are amplified and output by two "arms" of push-pull output stage in turn, and conduction time of each "arm" is a half-cycle of signal. The advantage of Class B amplifiers is high efficient, but downside is that they will create crosstalk.

Class A and B: Also known as class AB, it lies between class A and class B. The conduction time of each "arm" of push-pull amplification is greater than half waveform period and less than one cycle. . Class A and B amplifiers effectively solve crosstalk problem of class B amplifiers, and their efficiency is higher than that of class A amplifiers, so they are widely used.

Distortion: Device output cannot fully reproduce it instroke, resulting in distortion of waveform or increase or decrease in signal components.

Harmonic Distortion: Since amplifier is not perfect enough, in addition to amplified input components, output also adds some frequency components that are 2x, 3x, 4x... or even higher than original signal. (Harmonics), which distorts output waveform. This distortion caused by harmonics is called harmonic distortion.

Cross-over distortion: A type of distortion unique to Class B amplifiers. The mechanism of this distortion is that positive and negative half-cycles of signal are amplified by two different sets of devices respectively, and waveforms on both sides of positive and negative sides cannot be smoothly connected .

Audio coloration: The opposite of natural neutrality of music, that is, sound is colored by some characteristics that program itself does not have. For example, sound received when talking in a jar is a typical sound coloration. Coloration indicates that there are more (or fewer) components in reproduced signal, which is obviously distortion.

Sound pressure: a physical quantity expressing strength of sound.

Sound pressure level: sound pressure expressed in decibels.

Sensitivity: for amplifiers, Sensitivity usually refers to voltage of signal applied to input connector when rated output power or voltage is reached, which is why it is also called input sensitivity; for loudspeakers, sensitivity refers to an input power of 1 watt delivered to loudspeaker at a distance of 1 meter in front of loudspeaker. How many decibels of sound pressure can be produced.

Level: A general term for physical quantities such as voltage, current, and power in electronic systems. Levels are usually expressed in decibels (dB). That is, take voltage or current value as reference value (0 dB) in advance, take logarithm of ratio between expressed value and reference value, and multiply it by 20 as level number in decibels (level value). power level value is multiplied by 10).

Decibel (dB): Unit of measure for level and sound pressure level.

Damping factor: The ratio of load impedance to output impedance of amplifier. The output resistance of negative feedback transistor amplifiers is extremely small, only a few tenths of ohms or even less, so damping factor can reach tens and hundreds.

Feedback. Also known as feedback, a method in which some or all of output signal is fed back to input of an amplifier to change gain of circuit.

Negative feedback: feedback resulting in a decrease in magnification. Negative feedback can effectively widen frequency response and reduce distortion, although gain is lostso it is widely used.

Positive Review: Review that zooms in. Positive feedback is exact opposite of negative feedback, so it should be used with care.

Dynamic range: The level difference between strongest and weakest part of signal. For equipment, dynamic range refers to equipment's ability to handle both strong and weak signals.

Frequency response: referred to as frequency response, it measures equipment's ability to uniformly reproduce high, mid, and low frequency signals. There are two requirements for frequency response of equipment: one - range should be as wide as possible, that is, lower limit of reproducible frequency should be as low as possible, and upper limit should be Second, response of each point within frequency range should be as flat as possible to avoid excessive fluctuations.

Transient response: The ability of equipment to respond to a sudden signal in music. Equipment with good transient response should respond immediately when a signal comes in and stop abruptly when signal stops, never smoothly.

Signal-to-noise ratio (S/N). Also known as signal-to-noise ratio, contrast between useful signal components and noise is often expressed in decibels. A device with a higher signal-to-noise ratio indicates that it produces less noise.

Sine wave: The signal with most single frequency component. It is so named because waveform of this signal is a mathematical sine wave. Any complex signal, such as a music signal, can be viewed as a composite of many sine waves with different frequencies and sizes.

Wavelength: The movement of a sound wave in one cycle. The wavelength is numerically equal to speed of sound (344 m/s) divided by frequency.

Shielding: A technology in which electronic devices or wires are covered with materials that conduct electromagnetic waves easily so that external electromagnetic interference does not interfere with useful signals.

Impedance matching: A certain relationship must be maintained between output impedance of equipment and impedance of connected load, so as not to significantly affect operating condition of equipment itself after it is connected to load. For interconnection of electronic equipment, for example, signal source is connected to amplifier, and front stage is connected to rear stage, while input impedance of last stage is 5-10 times higher than output impedance. of previous step, we can assume that impedance matching is good, for connecting an amplifier. As for speaker, for a tube machine, you should choose a speaker with same or close to nominal impedance of its output end, and a transistor amplifier does not have such a limitation and can be connected to speaker with loveth impedance.

Burn: The process of preheating new equipment before use so that sound of equipment can enter a stable state