When to choose a pure post-stage power amplifier

People in the industry have always been very clear that the post-stage of integrated amplifiers below 10,000 yuan is not worth considering, especially the newly released integrated amplifiers, the post-stage is seriously reduced, and the power is falsely reported, which is extended to all integrated amplifiers.

In fact, many years ago, there was no such thing of cutting corners and falsely reporting power. Now it is found that the world is no longer what it used to be, and it is full of commercial deception. Many years ago, a small flagship amplifier worth tens of thousands of yuan was changed to a pure post-stage. After 60W×3+22W×4, HTPC+D2 was used to push 7 large boxes with great pleasure! . In the absence of a subwoofer, I felt a strong sofa **. On the contrary, today, in so many audio forums, what is talked about most is "not being able to push". Many manufacturers often have a nominal power of 100-200W×7, but there is still a saying that it is not being able to push, which makes me depressed and incomprehensible. I will no longer analyze why manufacturers do this. The post-stage of the amplifier must use a lot of copper and aluminum! Anyone who is a little older should know that copper and aluminum were only slightly more expensive than iron in the past and were worthless. Ordinary people had copper utensils everywhere. But what about today?

Many friends do not know what kind of performance the power amplifier should really achieve. They mistakenly believe that as long as the power is large enough, it is the king. They do not know the difference between the power amplifier of the integrated power amplifier and the pure power amplifier. Those friends always talk about "control power" and "resolution power", but they have no idea how the power amplifier can achieve these performances.

A friend once consulted me about a 2-channel pure power amplifier. I proposed the two extremely critical but unfamiliar concepts of "damping coefficient" and "conversion rate".

Basic indicators of power amplifiers: rated power.

Nowadays, power amplifiers in the United States and Europe are marked with rated power. Old power amplifiers are also marked with rated power. Generally, it is the power under very small distortion (such as 0.015%, the power measured at 20-20kHz, and more advanced power amplifiers are measured at 0.008%). In order to have a strong output power, a strong power supply is absolutely necessary! The power reflects the strength of the sound, that is, the volume.

The second basic indicator of the power amplifier: various distortions.

As shown above, this is directly related to the power. When the power of the power amplifier is large enough, and only a small part of its power is used, the distortion will be much smaller at this time.

The combined power amplifier backstage often only uses a pair of power tubes. The pairing of power tubes has a great influence on the distortion. In the past, high-end power amplifiers were paired directly on the production line of the device (for example, the distortion of the old power amplifier was very small, and the 10,000 yuan in those days was equivalent to 100,000 yuan today). The cost was very high, and today's power amplifiers within tens of thousands of yuan will not do this. Today, when the power tubes are not well paired, it is even more necessary to use their small power under high power to reduce the distortion. Distortion reflects the quality of the sound, that is, the texture.

An important indicator for high-end power amplifiers: damping coefficient.

In addition to power and distortion, the internal resistance of an advanced amplifier has a great impact on the control of bass quality. To ensure a small output impedance under high current conditions, high-quality high-power transformers, high-current rectifier circuits and powerful capacitor filter circuits are required. These things are not available in advanced integrated amplifiers due to space and cost constraints. Pure power amplifiers are several times better than integrated amplifiers in this regard. Secondly, in order to achieve strong output power and extremely small transistor output impedance, pure power amplifiers use several pairs of power tubes in parallel, and their control is also several times stronger than that of integrated amplifiers, while integrated amplifiers only use one pair of output power tubes (how many pairs of power tubes can be installed on such a small heat sink?).

Of course, the thickness of the speaker wire, the copper content and the quality of the terminal also have a direct impact on the damping coefficient. The damping coefficient reflects the quality of the amplifier's control over the bass, that is, the control.