Amplifier knowledge

In addition to portable playback devices, many enthusiasts are now beginning to understand how to match large speakers and power amplifiers, but AV power amplifiers, HiFi power amplifiers, high power, pure Class A, integrated, digital amplification, tube amplifiers, transistor amplification, field effect , pre-stage, post-stage... all kinds of nouns make people confused.

It is true that this knowledge is much more complicated than directly using active speakers to connect to a computer. In this series of pushes, we will focus on explaining these terms for entry-level users. Choosing a power amplifier brings some necessary help, so today we will first talk about some keywords about power amplifiers!

Pre-stage, pure post-stage, front-to-back combined

Many people can't tell the difference between the front and rear power amplifiers, and they don't know which one to buy. In fact, the functions of the front stage and the back stage are different. The front stage is generally a differential amplifier circuit or a common collector amplifier circuit. It mainly selects the differential mode signal that needs to be amplified from the signal, and it is usually connected to a multi-stage common-emitter amplifier circuit behind it. for small signal amplification. It is the signal voltage rather than the current that is boosted most likely at the front end.

Pure pre-stage circuit

To put it simply, the function of the pre-stage is to initially amplify the signal and realize volume adjustment and other functions. Most of the pre-amplifiers use this kind of active pre-stage circuit, rather than passive pre-amplifiers that can only adjust the volume. Of course, in addition to adjusting the volume, the active front stage can also perform preliminary amplification and reduce the internal resistance between the sound source and the rear stage to play a buffer role.

The rear stage is completely different from the front stage. It sends the signal from the front stage to the speaker and drives the speaker to produce sound.

Pure power amplifier

The pure post-stage input signal is very simple, it is to take over the output of the pre-stage and increase the power of the signal. The current stage is connected to the high-impedance post-stage, which mainly provides an appropriate output voltage, and the post-stage amplifier is connected to a low-impedance speaker to provide not only an appropriate voltage, but also sufficient current.

Therefore, a good post-stage system not only requires high power output, but also specifically indicates that it will be designed for high current. When the impedance of the load is reduced by half, the output power is doubled.

Integrated power amplifier for music facsimile

The most common one is the integrated power amplifier, which integrates the preamplifier and power amplifier into one body. This kind of amplifier has multiple input options for information sources, and has the level control function of the front stage. It integrates the left and right channels into one. When the signal source is at a certain input level, the amplifier output can be fully loaded.

Some of the consumer-grade amplifiers we often see and use are integrated designs, which are relatively more cost-effective than using separate pre- and post-amplifiers.

NAD's front and rear separated power amplifier

But there is no doubt that the design of split front and rear amplifiers is definitely better than the integrated power amplifier, because they each have a larger space and are more delicate. The design of the front and rear amplifiers together will inevitably cause some interference, which will affect the performance of details, and the separate front and rear amplifiers will give enthusiasts more choices to use with different equipment.

Many high-quality power amplifiers are pure pre-amplifier and pure post-amplifier systems with split design.

gallbladder machine, stone machine, front gallbladder and back stone

According to the different electronic components used, power amplifiers are further divided into tube amplifiers, stone amplifiers, gallstone amplifiers, and IC integrated circuit power amplifiers. Many concepts here also include tube power amplifiers, transistor power amplifiers, front gallbladder and back stones, etc., which are also easy to make people unpredictable.

A power amplifier that uses semiconductor devices as the amplification element is called a stone machine, because the crystal is extracted from stone; while a power amplifier that uses electron tubes as the amplification element is called a tube amplifier.

McIntosh's excellent tube amp 275

People often say that tube amplifiers are electronic tube amplifiers. Some electronic tubes are used for amplification, and some are used for polishing. The electronic tube amplifier has its own unique characteristics. Its sound is warm and durable, with excellent musicality, good atmosphere, and large distortion. Have a unique performance. Since the electronic tube is a voltage-controlled amplifier, most of its distortion components are even-order distortions, which happen to be octave harmonics in music performance. Not only does it sound like there is no blunt distortion, but it has a soft and sweet charm.

Adopt 300b push-pull tube power amplifier

However, electronic tubes have been eliminated in most industries due to their large size and high power consumption, and they are mostly used in music appreciation equipment. Most of the electronic tubes are replaced by small and power-saving transistors. The life of the transistor is very long. It sounds more mid-to-high frequency. The sound is dynamic and fast. It is obviously more suitable for performing some large dynamic music. . However, its sound is cold, especially the bass is not soft enough, and the treble will appear sharp, so it cannot be loved by all audiophiles.

Transistor power amplifier circuit

The power amplifier using the front gallbladder and the rear stone compromises the advantages of the two. It uses the electronic tube to amplify the sound signal in the front stage to make the input sound signal have good sound performance and high dynamic range, and finally make the sound more natural and harmonious. lifelike. Most of the post-stage power amplification part uses transistors to ensure the speed and power of the sound signal. It combines the advantages of the two and neutralizes the shortcomings of the two. It is a type of power amplifier that HiFi music lovers love very much. equipment.

The power amplifier circuit of front gallbladder and back stone

Although transistor power amplifiers and integrated amplifiers with front gallbladder and back stone have been loved by people since their appearance, but with the advancement of technology, the life of electron tubes has been better extended, and many people still have a soft spot for tube power amplifiers, while It is not to use modern stone machines or stone machines with front gallbladder and back stone. Although electronic tubes have been basically eliminated in other fields, the development of amplifiers has been getting better and better in recent years, which has also made electronic tubes continue to play an important role in the audio field.