When to choose a pure rear power amplifier

Insiders have always been very clear that the rear part of the combined power amplifiers below 10,000 yuan is not worth considering, especially the new combined power amplifiers, which have been severely shrunk afterwards, and the power is falsely reported, but expanded to all combined power amplifiers.

In fact, there was no such thing as cutting corners and falsely reporting power many years ago. Now I find that the arena is no longer what it used to be, and business deception is everywhere. Many years ago, a small flagship power amplifier with a value of tens of thousands of yuan was changed to a pure model, 60W×3+22W×4, using HTPC+D2 to push 7 large boxes into a tasteful! . In the absence of a subwoofer, everyone feels a strong sofa**. On the other hand, today, in so many audio forums, the most talked about is "can't move", and many manufacturers always use the nominal 100-200W×7 Power, but there is still a saying that I can’t move it, which makes me depressed and unable to understand. I will no longer analyze why manufacturers want to do this. After the power amplifier, copper and aluminum are used a lot! Anyone who is a little older should know that copper and aluminum were only a little more expensive than iron in the past, and they were not valuable. Ordinary people have bronze wares everywhere, but today?

Many friends don't know what kind of performance the power amplifier really wants to achieve. They mistakenly believe that as long as the power is large enough, it is the king, and they don't know the difference between a combined power amplifier and a pure rear power amplifier. Those friends talk about "control", "resolution" and so on, but they don't know how the power amplifier can achieve these performances.

A friend once consulted me with a 2-channel pure, and I proposed "damping coefficient" and "switching rate" two extremely critical but not very familiar concepts.

The basic index of the power amplifier: rated power.

Power amplifiers in the US and Europe are now marked with rated power. Old power amplifiers are also marked with rated power. Generally, it is the power when the distortion is very small (such as 0.015%, the power measured at 20-20kHz, the power amplifier is measured at 0.008%). If you want to have a strong output power, a strong power supply is absolutely necessary! The size of the power reflects the strength of the sound, that is, the sense of volume.

The second basic indicator of the power amplifier: various degrees of distortion.

The above has shown that this is directly related to the size of 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.

After combined power amplifiers, only a pair of power tubes is often used. The pairing of power tubes has a great influence on the distortion. The previous high power amplifiers are directly paired on the device production line (for example, the distortion of the old power amplifier is very small. Yuan should be equivalent to today's 100,000 yuan), the cost is very high, and today's power amplifiers with less than tens of thousands of yuan will not do this way. In today's poor pairing of power tubes, it is even more necessary to use its small power to reduce distortion under high power. The degree of distortion reflects the quality of the sound, that is, texture.

An important indicator for high power amplifiers: damping coefficient.

A high power amplifier, in addition to power and distortion, the internal resistance of its output has a great relationship with the ability to control the bass quality. To ensure that there is a small output impedance in a large current environment, first of all, there must be a high-quality high-power transformer, a large-current rectifier circuit and a powerful capacitor filter circuit. No matter how high these things are, the combined power amplifier will never be available due to space and cost constraints. The pure rear power amplifier is several times that of the combined power amplifier in this respect. Secondly, in order to achieve strong output power and extremely small transistor output impedance, the pure rear power amplifier uses several pairs of power tubes to work in parallel, and its control power is also several times stronger than the combined power amplifier, and the combined power amplifier only uses one. For the output power tube (see how many pairs of power tubes can be installed on such a small radiator?).

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 control quality of the power amplifier on the bass, that is, the control power.

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