In real life, most commonly used power amplifiers combine pre amplifiers and post amplifiers that amplify large and small signals into a single chassis. This type of power amplifier is commonly referred to as a "combined power amplifier". The advantage of a combined power amplifier is its convenience in use and superior product performance.

家用功放机

Household amplifier

然而，这种合并式功放有一些固有的缺点，其中不好克服的就是前级与后级之间的相互干扰问题了。为了解决这个问题，于是在设计上把前级功放与后级功放分别做在两个机壳中，这样就有了纯后级功放机。据数据显示，绝大多数的纯后级功放都是双声道的结构形式，但这种结构形式使得两个声道相互干扰问题又不太好解决。为了解决两个声道相互间的信号干扰，于是又出现了把两个声道分开的单声道纯后级功放机。单声道功放机的主要性能指标有：输出功率、频率响应、失真度、信噪比、输出阻抗、阻尼系数等。来自音源或前级放大器的弱信号放大，推动音箱放声。

However, this combined power amplifier has some inherent drawbacks, among which the most difficult to overcome is the mutual interference problem between the front and rear stages. In order to solve this problem, the front stage amplifier and rear stage amplifier were designed in two separate cases, resulting in a pure rear stage amplifier. According to data, the vast majority of pure rear stage power amplifiers have a dual channel structure, but this structure makes it difficult to solve the problem of mutual interference between the two channels. In order to solve the signal interference between two channels, a single channel pure post amplifier that separates the two channels has emerged. The main performance indicators of a mono amplifier include output power, frequency response, distortion, signal-to-noise ratio, output impedance, damping coefficient, etc. The weak signal from the sound source or preamplifier amplifies, pushing the speaker to play.

把功率放大器按功能区块分割开，其主要的意义是要提高功放机的性能，而不是追求这种形式的分开。如果仅仅在形式上实现了相互分开，尽管可以解决相互干扰问题，但其它参数并未明显改善，那么这种分开对功放提高整体性能来说还是非常有限的。

The main significance of dividing power amplifiers into functional blocks is to improve the performance of the amplifier, rather than pursuing this form of separation. If only formal separation is achieved, although it can solve the problem of mutual interference, other parameters have not been significantly improved, then this separation is still very limited in improving the overall performance of the power amplifier.

后级功放机

Rear amplifier

功率放大器有晶体管与电子管之分，前级同样也有晶体管和电子管之分。对于音响爱好者与音乐爱好者而言，在选用前级与后级上有多种的组合形式，而不同的组合形式又有不同的音效特点，这使得使用者又多了一些选择的空间。

Power amplifiers can be divided into transistors and electronic tubes, while the front stage can also be divided into transistors and electronic tubes. For audio enthusiasts and music enthusiasts, there are various combinations of front and rear levels to choose from, and each combination has different sound effects characteristics, which gives users more space to choose from.

与纯后级功放配接的前级对整个音响系统的优劣影响比较大。它必须具有一定的性能，否则，纯后级或是单声道的优点便发挥不出来，甚有可能把一台劣质前级的“毛病”突显出来，整体音效反而变得更不理想了。再者，不同的前级后级配合其音色特点不同，使用者可以根据个人的偏好选择不同的功放组合形式。

The front stage connected to the pure rear stage amplifier has a significant impact on the overall quality of the audio system. Firstly, it must have a certain level of performance, otherwise the advantages of pure rear stage or mono channel will not be fully realized, and it may even highlight the "problem" of a low-quality front stage, making the overall sound effect even less ideal. Furthermore, different front and rear stages, combined with their different timbre characteristics, allow users to choose different combinations of power amplifiers based on their personal preferences.

不难发现，很多音响与音乐爱好者就喜欢用“胆前、石后”（即电子管前级，晶体管后级）的组合方式，觉得这样组合既发挥了晶体管后级功率输出大，瞬态响应好的特点，又领略了电子管前级音色甜美、醇厚的韵味，不过这种搭配也并不是金科玉律,因为具体的前级与后级都有各自的特点，而对音色的偏好又因人而异，使用者可以根据具体的使用情况找出自己所喜爱的音响组合方式，从而获得更好的音效体验。

It is not difficult to find that many audio and music enthusiasts like to use the combination method of "gallbladder front, stone back" (i.e. electronic tube front stage, transistor rear stage), believing that this combination not only leverages the characteristics of high power output and good transient response of the transistor rear stage, but also appreciates the sweet and mellow tone of the electronic tube front stage. However, this combination is not a golden rule, as each specific front stage and rear stage have their own characteristics, The preference for sound quality varies from person to person, and users can find their favorite sound combination based on specific usage situations, thereby obtaining a better sound experience.