The difference between pre-amp and post-amplifier

The difference between pre-amp and post-amplifier

Summary

Power amplifiers are generally divided into pre-amplifiers, post-amplifiers, and combined-level power amplifiers. The combined machine is a machine that combines the pre-amp and post-amp. The front stage is used to initially amplify the signal and adjust the volume; the latter stage is to amplify the signal from the front stage to promote the speaker.

Many friends do not understand the difference between pre-amp and post-amp. Today I will explain the difference between the pre-amp and post-amp.

 Preamplifier is also the part that has the greatest impact on the tone of the whole set of equipment. It is the equipment that provides suitable audio level signals and adjusts the sound quality (connected between the sound source and power amplifier ).

Post-stage power amplifier is the real power amplifier part, which has a great influence on dynamics and low-frequency control. It is a device that simply amplifies the "pre-stage" audio signal to provide enough power to drive the speaker speaker to sound (always connect before the speaker).
The common power amplifier in the family audio should be called the pre and post combined power amplifier.

The input signal of the post-amp is very simple, which is to take over the output of the pre-amp. But the load of the post-amp is a speaker, which is what makes many audio fans and even magazine review writers confused. The post-amp is the load of the pre-amp, which is a high impedance load; the speaker is the load of the post-amp, which is a low impedance load. 

When the pre-amp is connected to a high-impedance post-amp, it mainly provides an appropriate output voltage. When the post-amp is connected to a low-impedance speaker, it must not only provide a suitable voltage, but also provide enough current.
Pure post-amp need to be driven by pre-amp. The power of pure post-amp is generally over a few hundred watts. It is usually used in some professional places, and multiple units work at the same time to drive different speakers. Therefore, the amplifier circuit does not have a low-level input port, or a socket for high-impedance input signals such as microphones, so it is necessary to add a preamplifier or mixer to the signal to control it. The pre-amplifier and pure post-amplifier are also combined into one. Usually the power is not more than 300 watts, and it is used in smaller places, home use or KTV.


Preamplifier refers to a circuit or electronic device placed between the signal source and the amplifier stage, and is designed to receive weak voltage signals from the signal source.

The preamplifier is used to amplify weak signals. Generally, the signal is first passed through an electrolytic capacitor to filter out high-frequency noise signals, and then enters the negative feedback operational amplifier to amplify the signal. Power amplifier generally refers to amplifying the power of AC signals, that is, amplifying the current and voltage of electrical appliances without distortion of the signal. The front is placed 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 pre-amplifier 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.

The preamplifier is generally connected to a pure post amplifier. The output of the preamplifier is connected to the input end of the post amplifier, and thepost amplifier can be connected to the speaker. The preamplifier is to amplify the voltage, and the pure post 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 and cannot promote the normal operation of the post amplifier. The pre-amplifier plays the role of signal amplification.

To sum up:

Amplifiers are generally divided into pre-amplifiers, post-amplifiers, and combined-level power amplifiers. The combined machine is a machine that combines the pre-amp and post-amp. The preamplifier is used to initially amplify the signal and adjust the volume; the post amplifier is to amplify the signal from the front stage to promote the speaker.
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