Detailed explanation of class AB power amplifier

Often much larger than class AB. Moreover, because of the high operating current, the working power voltage of Class A power amplifier is much lower at the same output power, so its peak output voltage is limited, and its input voltage is also limited by the amplifier amplification factor of the output voltage. Therefore, the great dynamic performance of music is affected.

The working conditions of the three amplifiers have been discussed in general terms from a theoretical point of view. Perhaps you will say that from the sound point of view, it is still the best class A! Yes, this is an objective fact, and the author does not deny it, but the problem is that the sound of a power amplifier is not only as simple as the above, the entire circuit and working principle are much more complicated, and various auxiliary circuits may be more complicated than the main amplifier circuit Much more, that is to say, even if you use the A type of amplification, it does not necessarily make a good noise.

Besides, the cost of a 100% class A power amplifier is also amazing, and its power consumption is more than an air conditioner. The so-called 100% Class A amplifier refers to how the impedance of the rateless speaker changes with frequency. The amplifier can maintain Class A work and the output power is sufficient. Although the nominal impedance of a pair of speakers is 8Ω, the actual impedance of the bacteria is working. It will change with frequency, it will be higher, it will be lower, it will be as low as 2Ω or even lower, which requires that the output power of the power amplifier can be doubled as the impedance decreases, which is the sky-high price of the Hi-End series we often see. The output power indicators of Class A amplifiers are 100W (8Ω), 200W (4Ω), 400W (2Ω) and 800W (1Ω). This is the so-called 100% pure Class A amplifier. Only such a power amplifier can make you always hear the sound of class A, but its price is also in the 100,000 yuan level, which is meaningless to most audiophiles.

Most of the low- and mid-priced A-type power amplifiers are only marked with 100w (8Ω) when the output power is marked. The following will not be marked. The implication is that this type of so-called A-type amplifier. When the speaker impedance is reduced, its A-class 100W Significantly reduced, the actual power amplifier works in Class AB working state most of the time, it should belong to Class AB, that is, its bias is higher than the threshold voltage mentioned earlier, which is usually called high bias current Class AB amplifiers are only intended to be expanded by manufacturers when they advertise. Generally speaking, reputable manufacturers will not say this. For example, Mark Levinson ’s No. 23.5 is an outstanding power amplifier. Its marked power is 200W (8Ω), class AB amplifier. It is equipped with two 1.2KVA large ring cattle. Actual It is estimated that 50W (8Ω) C or less is class A work, and class AB can contribute 248W (8Ω), but the factory has never been seen as a type A for publicity. To be honest, in terms of the limited machines I have heard, the difference between class AB and class A is very small. Therefore, many famous Hi-End factories do not promote themselves in category A, such as Jeff Rowland, etc., but their good voice is recognized.

In fact, what kind of circuit and working method a power amplifier chooses are not the only factors that determine the sound of the power amplifier, such as what we often say, the quality of the parts, the selection of the parts, the matching, and the production process are all factors that directly affect the sound. For machines with the same power, the capacity of Class A is 2 to 3 times greater than that of Class AB. It can be imagined that in the same price class, Class A machines almost use most of the cost for power supply, such as Krell KSA100 Class A 100W The power amplifier uses two 1.2KVA ring cattle and 160,000 microfarad electrolytic capacitors. If an AB class 100W amplifier uses two 600W ring cattle, it is very feverish and powerful. And it can use more costs for other aspects of the whole machine, and select more advanced parts. It has been proved that the serious production of class AB amplifiers will not be worse than the class A amplifiers of the same price, and the winners are also compared. Both are, therefore, I think that it is not incomplete to judge the sound from the categories A and AB. Rather, it is only the difference in the direction of the sound, but the difference in everyone's preferences. Taking Mark No. 23.5 mentioned above as an example, it is a class AB working state, but it is the value of a generation of famous machines. It is recognized by the Central Committee of the Audio Commission. To be honest, it is very difficult to surpass it at the same price for a class A amplifier. .

Take the 8000A class used by Wu Jun, a little more than 5,000 yuan (Wu Jun bought it at this price), 60W power, it is impossible to make a qualified A class 60W amplifier at this price. Besides, the voice 8000A is an evergreen tree with a reputation.

Besides, in the current domestic amplifiers, there are many serious and audible machines. The real class A machine has not appeared, at least I have not seen it; I have heard a 80W domestic machine not long ago, marked A The price is set at a very low price of 3,000 yuan, and the static body temperature is still warm for half an hour after the power is turned on. The ghost believes that it is a real class A, and it is not as good as a thousand yuan class AB. I always ca n’t figure it out. The audiophile ultimately depends on the ears. Then why do n’t you really do a good job of sound and power supply? Do you want to sell your machine? Why not do it? What about realistic gimmicks? People of Class A 50W use two 1000VA big ring cattle. It's not easy to talk about. We don't know, we can't do it, we just don't take it seriously. I also want to buy a 100% Class A machine. To be honest, Hi-End can't afford it. I hope to hear 100% of the beautiful Class A machines in the domestic machine as soon as possible.