Amplifier knowledge

                                                   Amplifier knowledge

Nowadays, in addition to portable playback equipment, many audiophiles have also begun 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 amps, transistor amplification, field effect , preamplifier, suffix... all kinds of nouns are confusing.

It is true that this knowledge is much more complicated than directly using active speakers to connect to the computer. In this series of updates, we will focus on explaining these terms for entry-level users. We hope to give everyone a basic understanding and help them understand themselves. Choosing a power amplifier brings some necessary help, so today we will first talk about some key words about power amplifiers!

Preamplifier, pure postamplifier, combined before and after

Many people can’t distinguish between the types of pre- and post-amplifiers, and they don’t know which one they should buy. In fact, the functions implemented by the front stage and the rear 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. It is usually followed by a multi-stage common emitter amplifier circuit. Used for small signal amplification. The signal voltage rather than the current is mostly increased at the front end.

Pure preamp circuit

Simply put, the function of the preamplifier is to initially amplify the signal and achieve volume adjustment. Most preamplifiers have this type of active preamplifier circuit, rather than passive preamplifiers that can only adjust the volume. Of course, in addition to adjusting the volume, the active preamp can also perform preliminary amplification and reduce the internal resistance between the sound source and the power stage to play a buffering role.

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

Pure power amplifier

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

Therefore, a good power stage system not only requires high power output, but also specifically specifies a large current design. When the impedance of the load is reduced by half, the output power is doubled.

Integrated amplifier for music fax

The most common one we have is the integrated power amplifier, which integrates the preamplifier and power amplifier parts into one body. This kind of amplifier has multiple sets of input sources for selection, and has a pre-level level control function. It integrates the left and right channels into one. When the signal source is at a certain input level, the amplifier output can be loaded with full power.

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 separate amplifiers

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

Many high-quality power amplifiers are pure preamplifier and pure postamplifier systems of split design.

Gallbladder machine, stone machine, front gallbladder and back stone

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

A power amplifier that uses semiconductor devices as its amplifying element is called a stone amplifier, because crystals are extracted from stones; while a power amplifier that uses electron tubes as its amplifying element is called a tube amplifier.

McIntosh's excellent tube amplifier 275

The tube amplifier that people often talk about is a tube amplifier. Some tubes are used for amplification, and some are used for polishing. The tube amplifier has its own unique characteristics. Its sound is warm and durable, with excellent musicality, good atmosphere, and large distortion. It is suitable for human voices. Has a unique performance. Since the vacuum tube is a voltage-controlled amplifier device, most of its distortion components are even-order distortion, which happens to be an octave harmonic in musical performance. Not only does it not sound like a harsh distortion, but it has a soft and sweet charm.

Using 300b push-pull tube amplifier

However, vacuum tubes have been eliminated in most industries due to their large size and high power consumption. They are mostly used in music appreciation equipment. Most vacuum tubes have been 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, and it is obviously more suitable when performing some large-dynamic music. . However, its sound is cold, especially the bass is not soft enough, and the treble is sharp, which makes it not loved by all audiophiles.

Transistor power amplifier circuit

The power amplifier that uses front and rear gallbladders compromises the advantages of both. It uses tubes in the front stage to amplify the sound signal so that the input sound signal has good sound performance and high dynamic range, ultimately making the sound more natural and harmonious. lifelike. Most of the post-stage power amplification parts use original transistors to ensure the speed and power of the sound signal. It combines the advantages of both and neutralizes the shortcomings of both. It is a type of power amplifier that is very popular among HiFi music lovers. equipment.

The power amplifier circuit of the front and back stones

Although transistor power amplifiers and combined amplifiers with front and back stones have been loved by people since their emergence, with the advancement of technology, the life of vacuum tubes has been better extended. Many people still have a soft spot for tube power amplifiers, and It is not about using modern stone machines or front and rear stone machines. Although vacuum tubes have been basically eliminated in other fields, the development of tube amps has been getting better and better in recent years, which has also made vacuum tubes continue to occupy an important position in the audio field.