Class A power amplifier can be said to be the originator of “stone machine”. It is the first generation of stone machine power amplifier, also known as class A power amplifier or pure class A power amplifier. Here is a point that needs to be specially explained. There is also a product called “Super Class A Power Amplifier” in the consumer market. “Super Class A Power Amplifier” is not a Class A power amplifier. It is actually another name for a Class AB power amplifier. Since class AB power amplifier is an improved product of class A power amplifier, some brands will call it “super class A power amplifier”, but in fact it is not what we call class A power amplifier.
One of the most widely circulated characteristics of Class A power amplifiers in the circle of HIFI enthusiasts is its very good sound quality. Many HIFI enthusiasts rank the sound quality of Class A power amplifiers first in their minds. So, is the sound quality of Class A power amplifier really as good as the rumors say? Can its sound fidelity be far ahead of other categories of power amplifier products? To clarify this issue, we need to systematically look at the development history of power amplifier products.
Class A amplifier design
Class A power amplifier is the first generation stone power amplifier product, its circuit design is relatively simple, and energy saving and other related factors are completely ignored. Its circuit design focuses on ensuring that it can provide sufficient output power to connect speakers. This simple design idea does guarantee the fidelity of the sound analog signal of the power amplifier to a large extent. The reason is that the simpler the circuit design, the fewer steps the signal in the circuit needs to be additionally processed. The higher the fidelity. Therefore, from the perspective of the original circuit design, the Class A power amplifier does have a natural advantage in sound quality.
Energy Consumption Performance of Class A Power Amplifier
However, such a minimalist design solution creates many other problems. The most prominent of these problems, and one that makes many HIFI enthusiasts look away, is the poor energy consumption performance of Class A power amplifiers. The performance of Class A power amplifiers in terms of power consumption is very unsatisfactory, and the energy efficiency ratio is only about 10%. That is to say, out of 100 watts of electrical energy, only 10 watts are used to drive the speaker to produce sound, and the remaining 90 watts of electrical energy are converted into heat by the circuit of the class A power amplifier and wasted. We can even say that Class A power amplifiers use most of the electric energy to generate heat, and only a handful of electric energy is actually utilized by the power amplifier.
One of the problems directly caused by the poor performance of energy consumption is that the “effective power” of Class A power amplifiers is low. After a class A power amplifier and a power amplifier with high energy efficiency are connected to the same speaker, the actual power consumption of the class A power amplifier will be several times that of other power amplifiers under the condition of outputting the same sound pressure level.
Cooling requirements of class A power amplifier
The second problem brought about by the high heat generation is that Class A power amplifiers have very high requirements for heat dissipation design and are extremely harsh. We can imagine that if the total output power of a class A power amplifier is around 400 watts, then 360W of electrical energy will be converted into heat. This is equivalent to a small heater with a power of 360W. Such a large heat generation requires very large heat dissipation fins, plus a fan for active cooling to remove this part of the heat from the body of the power amplifier.
On a high-power Class A power amplifier, once a cooling fan is installed, a certain amount of fan noise will be generated. This is a phenomenon that should not be underestimated. The noise produced by the fan when it runs at high speed is relatively easy for human ears to perceive.
This creates a “contradictory” performance. Class A power amplifiers are naturally famous for their high fidelity of sound, however, they suffer from the interference of cooling fan noise, which makes the expressiveness of sound quality somewhat flawed.
The cost of using a class A power amplifier
Another problem caused by the high heat generation of Class A power amplifiers is the relatively high cost of use. Even if the perfect heat dissipation design exhausts all the heat from the body of the power amplifier, the heat will still accumulate indoors. If the indoor ventilation is not good, the room temperature will rise slightly, and it can be used as a heater in winter.
If it is in summer, you must turn on the air conditioner to match the indoor temperature. In this way, the burden of double electricity bills will still bring some psychological discomfort to HIFI enthusiasts.
Class A amplifier weight
In addition, using an excellent heat dissipation design will also bring a disadvantage. That is, the volume and weight of Class A power amplifiers are often seriously beyond the normal range of a normal home audio equipment. Class A power amplifiers sold on the market above the 10,000 yuan level are often well designed in terms of heat dissipation. But if HIFI enthusiasts pay attention to the specific parameters of these products, you will find that it is not uncommon for a Class A power amplifier to weigh 30KG.
In actual use, such a heavy power amplifier will be very inconvenient when placed and moved. For HIFI enthusiasts who love toss, this is not good news. If you have the habit of changing audio equipment frequently, then Class A amplifiers will be particularly time-consuming and laborious when replacing equipment. Generally speaking, Class A power amplifiers are still suitable to be placed in relatively large living rooms, and are suitable for HIFI enthusiasts who like to arrange the audio equipment once and for all.
Nowadays, many optimization measures have been added to the circuit design used in other categories of power amplifier products. In fact, the gap between the sound quality and the class A power amplifier is not very big, or ordinary consumers may not be able to hear the difference. . The fidelity of the audio signal of the Class A power amplifier is actually not as “mythical” as advertised by the merchants.
Of course, if economic conditions permit, buying a Class A power amplifier and playing with it is also a way for a HIFI enthusiast to broaden his horizons. However, if a HIFI enthusiast is only going to buy a power amplifier device. Then, there is no need to be too obsessed with the sound quality performance of the Class A power amplifier. After all, considering all the power amplifier parameters, the Class A power amplifier is by no means the most “top” power amplifier product.
Every one of us HIFI enthusiasts should understand one thing. It is some problems and shortcomings of the class A power amplifier mentioned in this article, which will not be improved with the development of technology. These defects are congenital problems caused by the circuit design of Class A power amplifier itself. If the circuit design is completely subverted, then such a power amplifier cannot be called a Class A power amplifier.
In fact, a series of power amplifier products that appeared after Class A power amplifiers have actually made up for these shortcomings of Class A power amplifiers. However, due to the difference in circuit design, they are all named in the form of a separate type of power amplifier product.
In terms of price, most of the Class A power amplifier products that can be purchased on the market appear in a high-end image, and the price remains high. If it is a Class A power amplifier product of an imported brand, the price generally starts at 50,000 yuan, and some manufacturers of domestic brands can start with less than 10,000 yuan. Audio HIFI enthusiasts with greater economic affordability can try it, but it is not recommended for all HIFI enthusiasts to try it out.