Introduction to Audio Introduction of Analog Audio System

- Jun 29, 2020-

The current audio system is definitely inseparable from digital equipment and digital circuits, but to briefly introduce the introductory knowledge of audio, it is still necessary to make it clear that the most "old" audio of human beings: analog equipment.


We know that motors and motors are actually a kind of thing. When you turn the motor, you can output current, and when you supply current, the motor will turn, and the microphone and speaker are also the same thing: the microphone picks up sound waves and outputs audio current signals, amplified audio The current can drive the horn to emit sound waves. In the structure of the current sound system, the equipment that emits sound waves includes speakers (speakers), headphones, and microphones and pickups for picking up signals, but most people generally do not need microphones and pickups. Basically, they are now digital sound sources. Analog sound sources, cassette players have become antiques, and radios are rare, but vinyl is a bit of a comeback.


The vibrations picked up by the microphone and the phono are converted into audio currents through magnetic and electrical structures. This is the "analog signal". The audio signal picked up by the microphone and the phono is very weak, and the current is very small. It must be amplified by the "microphone amplifier, circuit", "phono amplifier, circuit" to reach the "line signal" level of about 1v. In the current audio system, most of the connected equipment are mostly "line signals" (labeled LINE in English), and the receiver, TV set-top box, CD player, portable player, etc. are connected to the amplifier Is the line signal. Many audio equipment will provide red and white signal lines, which transmit analog line signals.


Many people use a mobile phone to connect to the stereo and use a 3.5-turn dual lotus cable. Because the current of the amp circuit of the mobile phone is not large, it is basically similar to the line signal, so it is also possible. Attentive users will find that some portable players and portable decoding amp all-in-one machines distinguish between the headphone port and the LO port (either by lever or system setting). Although the headphone port can actually be connected to the power amplifier, the LO port provides It is the line level (LO is the abbreviation of Line Out line output), and the sound will be better.


The line signal can be amplified by the power amplifier to drive the speaker; through the headphone amplifier, it can match the headphones with various impedances. The power of most power amplifiers at normal output is more than ten watts, and the voltage is tens of volts. In traditional analog power amplifiers, the line signal is amplified by the previous stage and the voltage is amplified to drive the current amplification stage. These are combined in a single chassis to be "merged amplifier" Some audiophiles will use the front and back stages, that is, make the pre-amplifier circuit into a single piece of equipment, called "pre-stage", and the voltage and current amplification is the "post-stage". It should be noted that there is no volume adjustment for the power amplifier. Because the components and output of digital equipment and portable equipment are very powerful, in fact, mobile phones, players, and integrated decoders can directly drive the latter stage, but pay attention to the volume control when connecting. This is an off-topic.


In fact, in the 21st century, if there is no resurgence of vinyl, basically there will be no complete, pure analog system. In real life, the sound waves picked up by the microphone will be converted into digital signals for processing and recording. Even for vinyl records, most of them are digitally recorded and then simulated.


Briefly introduce the pure analog system in the title map: German clear vinyl record player, Danish high wind cartridge, the new American amp (the one with the headset underneath), and the American speaker. The new HPA-9 amps and preamps use single-ended, pure class A, and no negative feedback circuits. They are very old analog amplifier circuits; instead, the amp part uses op amp ICs, which are relatively new circuits, but It is also a pure analog circuit. This headphone system, coupled with the post-stage power amplifier and speakers, is a pure analog large system.