People in the industry have always been very clear that the post stage part of the combined power amplifier below 10000 yuan is not worth considering, especially the new combined power amplifier, which has seriously shrunk and falsely reported power, is expanded to all the combined power amplifiers.

In fact, many years ago, there was no such thing as cutting corners and falsely reporting power. Now I find that the world is not what it used to be, full of business fraud. Many years ago, a small flagship power amplifier with tens of thousands of yuan was changed into a pure rear stage, 60W × 3 + 22W × 4, and HTPC + D2 was used to push seven large boxes to make them very interesting!. In the absence of subwoofer, we all feel a strong sense of anxiety. Today, in so many audio forums, what we talk about is that we can't push. Many manufacturers can't push the nominal power of 100-200W × 7, but I'm still depressed and can't understand it. I don't want to analyze why manufacturers do this anymore. The latter stage of power amplifier is to use a lot of copper and aluminum! As long as people are a little older, they should know that copper and aluminum used to be a little more expensive than iron, and they are worthless. Ordinary people have bronze wares everywhere, but what about today?

Many friends don't really know what kind of performance the power amplifier really wants to achieve. They mistakenly think that as long as the power is large enough, it is the king's way. They also don't know the difference between the post stage and pure post stage of the combined power amplifier. Those friends want "control" and "analytical power" when they talk, but they don't know how the power amplifier can achieve these performances.

A friend once consulted me about a 2-channel pure rear stage, and I put forward two key concepts of "damping coefficient" and "conversion rate", which are not familiar to everyone.

The basic index of power amplifier: rated power.

Nowadays, power amplifiers in the United States and Europe are marked with rated power. The old power amplifier is also marked with rated power. Generally, the power is measured under the condition of small distortion (such as 0.015%, 20-20KHz, and 0.008% for more advanced power amplifier). To have a strong output power, a strong power support is absolutely necessary! The power reflects the strength of the sound, that is, the sense of quantity.

The second basic index of power amplifier: various degrees of distortion.

It has been shown that this is directly related to the power. When the power of the amplifier is large enough and only a small part of the power is used, the distortion will be much smaller.

The post stage of the combined power amplifier often only uses a pair of power transistors. The pairing of power transistors has a great impact on the distortion. In the past, the high-level power amplifier was paired directly to the production line of the device (for example, the distortion of the old power amplifier was very small, and the 10000 yuan in that year was equivalent to 100000 yuan today). The cost is very high, and the power amplifier with tens of thousands of yuan today will not do this. In today's power transistor pairing is not good, we need to use its small power to reduce the distortion under high power. Distortion reflects the quality of sound, that is, texture.

Advanced power amplifier has an important index: damping coefficient.

In addition to the power and distortion of an advanced power amplifier, the output internal resistance has a great influence on the control ability of bass quality. To ensure a small output impedance in high current environment, it is necessary to have high-quality high-power transformer, high current rectifier circuit and powerful capacitor filter circuit. No matter how advanced these things are, the combined power amplifier will never be available due to the limitation of space and cost. And the pure power amplifier in this aspect is several times more than the combined power amplifier. Secondly, in order to achieve strong output power and minimal transistor output impedance, the pure post stage power amplifier uses several pairs of power transistors to work in parallel, and its control power is several times stronger than the combined power amplifier, while the combined power amplifier only uses one pair of output power transistors (see how many pairs of power transistors can be installed in such a small radiator?).

Of course, the thickness of the horn wire, the copper content and the quality of the terminal also have a direct impact on the damping coefficient. The damping coefficient reflects the control quality of the power amplifier to the bass, that is, the control force.