Many friends do not understand the difference between the pre-amplifier and the post-stage. Today I will explain the difference between the front stage and the back stage of the power amplifier.
The professional name of the preamplifier is: preamplifier. It is also the part of the whole equipment that has the greatest impact on timbre, it is a device that provides a suitable audio level signal and adjusts the sound quality (commonly known as a preamplifier, connected between the audio source and the power amplifier).
The professional name of the post-level amplifier is: pure post-level amplifier. This is the real amplifier part, which has a big impact on dynamic and low-frequency control. It is a device that simply amplifies the “pre-stage” audio signal to provide enough power to drive the speaker to sound (always connected to the speaker).
And the common power amplifier in the general family should be called the front and rear stage combined amplifier, combined power amplifier.
Post-stage amplifier (pure post-amplifier):
The input signal of the later stage is very simple, that is, to undertake the output of the previous stage. But the load of the rear stage is the horn, which is what makes many audio fans and even magazine review writers confused. The rear stage is the load of the front stage, which is a high impedance load; The horn is a load in the second stage, which is a low impedance load. It looks similar, only one word apart, but the high and low impedance cause the phenomenon that it is easy to push or not push. The current stage is connected to a high impedance secondary stage, which mainly provides the appropriate output voltage, because the rear stage expander.
Pure post-stage power amplifier needs a preamplifier to push, pure post-stage power amplifier power is generally very large in more than a few hundred watts, usually used in some professional places, and multiple simultaneous work to promote different speakers, because it itself does not have a pre-amplification circuit so there is no low-level input port, no microphone and other high-impedance input signal sockets, which requires him to add a preamplifier or mixer to the signal to control it. Preamplifiers and pure post-stage amplifiers are also combined, usually with little power below 300 watts, and are used in smaller places, home use or KTV and other uses.
A preamplifier is a circuit or electronic device placed between a source and an amplifier stage and is designed to accept a weak voltage signal from a source.
Preamplifiers are used to amplify weak signals, generally by first filtering out high-frequency noise signals through electrolytic capacitors, and then entering negative feedback to amplify the signal. Power amplifier generally refers to the power to amplify the AC signal, that is, to amplify the current and voltage of the electrical appliance without distortion. The front is tightly 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 pre-amplified to reduce the relative impact of external interference. The preamplifier is designed for high input impedance and low output impedance for impedance conversion and matching.
If you talk about technology alone, the front stage is more refined than the rear stage, and it is more difficult to do a good job, if you want to add a special power line, you must not use a good line in the rear stage because of the large current of the rear stage, it should be the front stage.
The preamplifier is generally connected to a pure post-stage power amplifier, the pre-stage output is connected to the input of the post-stage, and the post-stage is connected to the speaker. The preamplifier is an amplification voltage, the pure post-amplifier is an amplification current, the preamplifier is a link device between various audio source equipment and power amplifier, the output signal level of the audio source device is relatively low, can not promote the normal operation of the power amplifier, and the preamplifier is to play the role of signal amplification.
Power amplifiers are generally divided into pre-stage power amplifiers, post-stage power amplifiers and merger-level power amplifiers, and the merging machine integrates the front and rear stages into one. The front stage is used to initially amplify the signal and adjust the volume; The rear stage amplifies the signal from the front stage to push the speaker.