At present, Class D digital power amplifier is very popular, which is better than the traditional Class A and Class AB power amplifiers?

For people who don't know technology, class A power amplifier is the best. That was not the case. On the premise of the same cost, the performance and hearing of class D power amplifier far exceed that of class A. ..

There are two reasons. First, class A power amplifier has a fatal disadvantage, not high power consumption. Instead, two transistors with different polarities are used to amplify the positive and negative half cycles of the signal respectively. This leads to a fatal problem. There are no two transistors with the same performance in the world. That is to say, the upper and lower waveforms were originally emitted by the same object, but you divided them into two different tubes to amplify them. The upper and lower waveforms are inevitably distorted and cannot overlap perfectly. The class D power amplifier uses the output power of the switch tube, which means that the switch has nothing to do with the magnification, which can greatly reduce the matching pressure of the power tube, and will not lead to the inconsistency of the upper and lower waveforms due to the magnification or other performance. Some people will say that the output tubes of Class A power amplifier are strictly matched, and the magnification is seriously consistent. Actually, it's just that there's no way to say it. The amplification performance of transistors is different in different environments. For example, at different frequencies, the magnification is different. Usually just do DC amplification matching. So don't be superstitious about your strict pairing.

The second fatal shortcoming of class A power amplifier. It's the dual power supply. The upper and lower half-cycle signals are powered by the upper and lower positive and negative power supplies respectively. No matter how high-tech, it is impossible to get two identical transformers, especially the internal resistance will be different. Inconsistent internal resistance of power signal channel will lead to distortion of upper and lower waveforms. This problem cannot be avoided. The class D amplifier can use a single power supply, and there is no such problem at all.

So from a technical point of view, class D amplifier can easily beat class A amplifier. Then why do many experts say that class A amplifiers can't beat class D at all? There are two reasons. The first is that the cost is different and the natural hearing is different. The second reason is that the master is used to Class A and feels good, but nothing else is good, which is purely subjective.

The final conclusion is that the sounds of Class A and Class D are definitely different. Which one is better depends on your preference. However, I can tell you responsibly that class D amplifier can better restore the real sound, and it is technically easier to do better. Whether you like it or not is just a matter of personal preference.

In the past two years, I have installed three Class A and Class D amplifiers, and then I have been listening to AB. Generally speaking, Class A is resistant to listening, and the reason of being tall can only play a bluff role. Let me briefly describe it with "human words".

I saw someone say that one of the shortcomings of class D power amplifier is that it is noisy. Seriously, it is directly transmitted to the speaker. I suspect that the person who said this has never been exposed to class D amplifiers, or has been exposed to inferior class D amplifiers. As we all know, the real class D power amplifier will not have the noise of the traditional transformer because of the switching power supply. On the contrary, the class D amplifier is so quiet that people wonder if it is turned on.

It is not scientific to say that Class A is not hot or pleasant to listen to. This is related to whether the power amplifier uses current amplification or voltage amplification, and has nothing to do with whether it sounds good or not. The current is amplified and the temperature rises very quickly.

Class d is generally used in summer, and the fever is small. At other times, of course, you can also use Class A in summer. Class A is used in winter now, and the heat is also very high. However, a qualified power amplifier, heated to a certain extent, will be relatively constant and not so terrible.

In short, there is little difference between the two, but from the psychological impact, I feel that Class A is more resistant to listening. Over time, just as digital cameras replace film cameras, class D power amplifiers will replace traditional power amplifiers with high power consumption and high cost. In fact, foreign professional manufacturers have already done this.

This is a topic that causes a fight, and you will avoid discussing it abroad. Because the place used is different from the thing in charge. As far as the cost is concerned, Class D is used in hearing AIDS, telephones and individual subwoofers, with small size, light weight and low heating efficiency. Society needs a D-level, and the important thing is that a good D-level is not cheap. In addition, although its power is high, it is mostly used in subwoofers because people are not sensitive to bass, whether it is distortion or other defects. Class A and electron tubes are suitable for bookcase speakers, generally suppressing high notes and details, because it enhances the alto, which is the most sensitive thing for human beings. Therefore, the elderly should listen to the details in the music or choose Class B. In addition, if you have a loudspeaker over 8 inches, the performance of Class A will be poor, because if you can't push it, the whole thing will be in chaos. Class B is the largest power amplifier at present. When the static current of 30ma is increased, it has no cross distortion. It needs a small radiator (Class D also generates heat) and has high conversion power. Equipped with rated power transformer, it can obtain 3/4 power utilization rate, and can also carry out various combined transformations, high voltage and so on. If the Class D amplifier is the lowest noise amplifier you have ever heard, you must have never heard of a field tube amplifier, and you can also achieve deep silence. No one is a fool to listen to such a big transformer for a loudspeaker, because if you install a class H field tube and drive a loudspeaker with a power exceeding 1.500 watts, you don't need other types of power amplifiers, which is the strongest combination of 1.2 inches.

Power amplifiers are used in different places, just like music, and everyone has different taste requirements. If you listen to Class A for the elderly, you might as well listen to Class B for him. He likes to listen to details, and his voice is harder and sharper. Some characteristics of human beings are: after having a big horn, come and blow me up, and then the choice is different.

The difference between decoders is modulation distortion, which is the same as the principle of guitar effector, because the theoretical distortion of 100 yuan decoder and 100 yuan decoder was already at the same level 20 years ago. The built-in onboard sound card is enough. From the low-end to the high-end, foreign countries have done 100 blind listening tests, and no one guessed the value of the decoder.

Therefore, whether a power amplifier is good or not has the following incredible comments: no noise is the first requirement, and whether it is high or not depends on noise. The appearance is very important, which determines the difference between several thousand yuan and tens of thousands of yuan. Whether there are many tubes or not, the winner of thousand yuan is not divided here, so just push it, the winner of one hundred yuan, the model of the amplifier of several tens of yuan, and the distortion.

Hifi users said that they took the A and B DH tubes as the goal, the matching degree of supporting speakers as the criterion, and the low distortion and high aesthetic tone as the loyal goal, and immediately switched to the decision I said when they really paid for it.

The sound quality principle of audio power amplifier is that the sound quality is inversely proportional to the efficiency, and you can't have your cake and eat it. According to the sound quality, they are: electron tube A, electron tube AB, transistor A, transistor AB and digital power amplifier. If you sort by efficiency, it's just the other way around. Note that the human ear's preference for sound quality does not depend on the size of distortion, but naturally likes even harmonics, so the current 24-bit and even exaggerated 32-bit decoders are 100% useless and pure commercial gimmicks!

In terms of sound, the main factors that affect the listening effect are sound source and sound box, especially sound box. Different brands vary greatly, and the listening effect of the whole sound system mainly depends on the speakers. As for power amplifier, the difference lies in the types, such as electron tube (gallbladder machine), transistor (stone machine), digital power amplifier and so on. Gallbladder machine can be divided into unilateral A type and push-pull type, and calculus machine can be divided into A type and A type (B type rarely appears in heating sound). Recognized listening effect order: unilateral A, gallbladder push-pull, A, A, B, digital power amplifier. Among the three parts of the sound system, the power amplifier is the most easily homogenized. Whether it is a big brand or a small brand, as long as you don't cut corners, the sound effect won't be much different! Back to the topic, as a new thing, digital power amplifier is mainly used on the stage and will not be accepted by the fever community in the short term. As a pioneer of digital audio, when the cd player first came out, many people complained about its digital taste. Although the indexes of cd are far superior to vinyl and tape in the same period, the listening effect is hard to be recognized. Even now, the sound effects of vinyl and magnetic tape can't be compared with those of cd, but as digital power amplifiers, they can't be compared with the first two at least in the short term.

In the past, we called class A power amplifier, class B power amplifier, class A and B power amplifier and digital power amplifier. Digital power amplifier is energy-saving, light weight and easy to carry, otherwise it really has no advantage. Class A power amplifier is full power as soon as it is turned on. Suddenly a high note will not be distorted, and the shortcomings are obvious. Contrary to Class A, Class B power amplifier can't work without signal. The disadvantage is that there is a certain lag, and the advantage is that there is basically no communication sound. Class A and Class B are between Class A and Class B, with half power. They have the advantages of Class A and Class B, but they also inherit the disadvantages of Class A and Class B. As for the digital amplifier, it would be nice to be a toy. . . . .

Just these days, I'm studying class D power amplifier, so I just want to say a few words. Compared with Class A and Class AB power amplifiers, Class D power amplifiers have many advantages, but the disadvantages are also obvious: it is difficult to achieve the ultimate sound quality. There are three main reasons. When the output tube of Class I and D power amplifier is turned on, the power supply is directly connected to the output end, and the power supply noise is directly output to the speaker. Secondly, the jitter contained in the triangular wave sampled from the input signal will be modulated on the output signal, which will obviously deteriorate the listening sense. Thirdly, the dead time of the output switch tube will cause huge THD distortion, and the dead time of 10ns is enough to cause 1% THD distortion. These problems are difficult to solve and test the level of designers. In consumer digital products, such as TV, mobile phone and cheap home theater, which have low requirements on sound quality and are sensitive to volume, power consumption and cost, class D power amplifier has an absolute advantage, and there are almost no class A and AB power amplifiers now. Audio enthusiasts who pursue the ultimate sound quality are generally not interested in class D power amplifiers, preferring class A and AB power amplifiers with greater power consumption and heavier weight. There is even a saying among enthusiasts: the power amplifier is not hot or pleasant to listen to, and it is not heavy or pleasant to listen to.

Simply put, class A power amplifier is full-wave sine wave amplification, with low efficiency but good sound quality. Class-B power amplifier consists of two amplifiers at the output end, plus or minus half a cycle, with high efficiency but distortion. Class AB power amplifier consists of Class A and Class B, which avoids the problems of Class B distortion and Class A inefficiency. At present, Class D power amplifier is widely used, which has excellent noise reduction and anti-interference ability that Class A or Class AB cannot easily achieve. It has small volume and high efficiency. If well-matched components are used, the sound quality can reach the AB effect, which is currently used in multimedia active speakers.

At present, there are still some problems in Class D, which are mainly manifested in frequent paste at high frequency and lack of layering and air sense, which is determined by the structure of Class D power amplifier. For fast-changing signals, the LC element at the output terminal is easy to oscillate and can only suppress low-resistance oscillation. However, the horn impedance changes too much to suppress the oscillation well, so the sound is mushy and lacks details. There are still some ways to solve the problem. The introduction of 4-6dB local feedback in the later stage can significantly improve the oscillation caused by LC elements and greatly enhance the layering of music. In this way, the sound quality of well-designed class D power amplifier can still reach or even exceed that of class AB power amplifier.

Extreme pursuit of metamorphosis