What is a pre-amplifier and what is a post-amplifier?

                                      What is a pre-amplifier and what is a post-amplifier

Since you want to assemble a home theater, you must first understand the functions of each device, and the power amplifier is no exception. You must know what it does and what it is used for.

What is an amplifier?

Amplifiers, to be precise, are receivers and loudspeakers. English is Receiver, which means to receive audio and video signals and process them to obtain better audio and video effects and output them to video equipment (TV, projector) and audio equipment (speakers).

Why do you need an amplifier?

Power amplifiers are generally divided into front-level power amplifiers, rear-level power amplifiers and combined power amplifiers (commonly known as combined machines). A combined machine is a machine that integrates the front stage and the back stage. The front stage is used to initially amplify the signal and adjust the volume; while the rear stage is to amplify the signal from the front stage to drive the speaker.

For Hi-Fi and home theater at this stage, the power amplifier is not just as simple as power output. For Hi-Fi, it needs to analyze the basic sound, restore the sound effect as much as possible, and then amplify it , let the speakers produce sound, and ensure the output of sound quality details. For home theaters, it is even more practical. It can separate audio and video signals, and then perform decoding and image quality enhancement processing, and finally output to TV/ Projectors and speakers have achieved a more perfect effect.

Another point is that the signal source input interface and output interface that comes with the power amplifier are obviously more than those that come with the player. If you connect more equipment, the power amplifier can help you integrate management and switch outputs.

Post-stage power amplifier (pure post-stage power amplifier):

The input signal of the rear stage is very simple, it is to undertake the output of the previous stage. The latter stage is the load of the former stage, which is a high-impedance load; the speaker is the load of the latter stage, which is a low-impedance load. It looks almost the same, only one word is missing, but the high and low impedance makes it easy to push or not to push. The current stage is connected to a high-impedance post-stage, which mainly provides an appropriate output voltage because of the post-stage amplifier.

The pure post-stage power amplifier needs a preamplifier to drive. The power of a pure post-stage power amplifier is generally more than a few hundred watts. It is usually used in some professional places, and multiple units work at the same time to drive different speakers, because it does not have a preamplifier. Therefore, the circuit has no low-level input ports, no jacks for high-impedance input signals such as microphones, which requires adding a preamplifier or a mixer to the signal to control it. The preamplifier and the pure post-amplifier are also combined into one, usually with a power of less than 300 watts, which is used in smaller places, such as home use or KTV.

Preamplifier (preamplifier):

A preamplifier is a circuit or electronic device placed between the source and the amplifier stage, designed to accept a weak voltage signal from the source.

The preamplifier is used to amplify the weak signal. Generally, the signal is passed through the electrolytic capacitor to filter out the high-frequency noise signal, and then enters the negative feedback to amplify the signal. A power amplifier generally refers to amplifying the power of an AC signal, that is, amplifying the current and voltage of an electrical appliance without distorting the signal. The pre-amplifier is close to the detector, the transmission line is short, the distributed capacitance Cs is reduced, and the signal-to-noise ratio is improved. The signal is initially amplified by the preamplifier to reduce the relative influence of external interference. The preamplifier is designed with high input impedance and low output impedance to achieve impedance conversion and matching.

If we only talk about technology, the requirements of the front stage are more precise than the back stage, and it is more difficult to do well. If you want to add a special power line, you must not use a good line for the back stage because of the large current of the back stage. It should be the front stage. class.

The preamplifier is generally connected to the pure post-stage power amplifier, the output of the pre-stage is connected to the input of the post-stage, and the post-stage is connected to the speaker. The preamplifier is to amplify the voltage, and the pure post-stage power amplifier is to amplify the current. The preamplifier is the link device between various audio source equipment and the power amplifier. The output signal level of the audio source equipment is relatively low, which cannot promote the normal operation of the power amplifier. The preamplifier plays the role of signal amplification.