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The difference between the pre-level and the post-level amplifier

All are amplifiers, but the role is different! Many friends don't understand the difference between the preamp and the post. Today, let's explain the difference between the preamplifier and the postamp.


The professional name of the preamp is: the preamplifier is also the most influential part of the sound in the whole set of equipment. It is a device that provides suitable audio level signals and adjusts the sound quality (commonly known as preamplifier, connected to the sound source and power amplifier). between).

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The professional name of the post-amplifier is: pure post-amplifier This is the real power amplifier part, which has a great influence on dynamic and low-frequency control. It is simply a device that amplifies the "pre-stage" audio signal to provide enough power to drive the speaker horn (always connected to the speaker).


The common power amplifiers in the general family should be called the front-and-back level combined amplifiers, and the amplifiers are combined.


After-stage power amplifier (pure final stage power amplifier):

The input signal of the latter stage is very simple, that is, the output of the previous stage is taken. But the load in the post-stage is the horn, which is what makes many audio fans and even magazine commentators. The latter stage is the load of the front stage, which is a high impedance load; the horn is the load of the latter stage and is a low impedance load. It looks almost the same, only one word, but the impedance is high and low, which makes it easy to push or push. The current stage is connected to the high-impedance post-stage, which mainly provides the appropriate output voltage because of the post-amplifier.

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Pure post-amplifiers need preamplifiers to drive. Pure post-amplifier power is generally more than a few hundred watts. It is usually used in some professional places, and multiple machines work at the same time to drive different speakers, because it is not pre-positioned by itself. The amplifying circuit therefore has no low-level input port and no high-impedance input signal jack for the microphone. This requires a preamplifier or mixer to signal it to control it. The preamplifier and the pure final stage power amplifier are also combined into one, usually less than 300 watts, which is used in smaller places, for home use or KTV.

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Preamplifier (preamplifier):

A preamplifier is a circuit or electronic device placed between a source and an amplifier stage and designed to accept weak voltage signals from sources.

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The preamplifier is used to amplify the weak signal. Generally, the signal is first filtered through the electrolytic capacitor to filter out the high frequency noise signal, and then enters the negative feedback op amp to amplify the signal. A power amplifier generally refers to amplifying the power of an AC signal, that is, a current and a voltage of an amplifying device in the case where the signal is not distorted. The front is placed close to the detector, the transmission line is short, and the distributed capacitance Cs is reduced, which improves the signal-to-noise ratio. The signal is initially amplified by the preamplifier to reduce the relative influence of external interference. The preamplifier is designed for high input impedance and low output impedance for impedance conversion and matching.


If the technology is single, the pre-level is more precise than the latter, and it is more difficult to do. If you want to add a special power line, you must not use the good line in the post-stage because the post-stage current is large. It should be before. level.


The preamplifier is generally connected to the pure final stage power amplifier, the front stage output is connected to the input stage of the rear stage, and the rear stage is connected to the speaker. The preamplifier is an amplifying voltage, and the pure final stage power amplifier is an amplifying current. The preamplifier is a linking device between various audio source devices and a power amplifier. The output signal level of the audio source device is relatively low, and the power amplifier cannot be driven normally. The preamplifier acts as a signal amplifier.


to sum up:

The power amplifier is generally divided into a pre-amplifier, a post-amplifier and a combined-level power amplifier, and the merger machine combines the pre-stage and the post-stage in one machine. The front stage is used to initially amplify and adjust the volume; while the latter stage is to amplify the signal from the previous stage to drive the speaker.


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