Which is better, a tube amplifier or a transistor

by:Gisen     2020-03-26
Comparison of tube amplifier and transistor amplifier 聽Circuit characteristics Transistor amplifiers work under low voltage and high current. The working voltage of the power amplifier stage is within tens of volts, and the current reaches several amps or tens of amps. The circuit design mostly uses direct-coupled (OCL, BTL, etc.) non-output transformer circuits, and the output power can be made very large, up to hundreds of watts, and the electrical performance is very high. Tube amplifiers work under high voltage and low current conditions. The terminal voltage of the final power amplifier tube can reach 400-500V or even thousands of volts, while the current flowing through the tube is only tens of milliamps to hundreds of milliamps. Large input dynamic range and fast conversion rate. Most of the tube amplifiers use discrete components, manual wiring and welding, which have low efficiency and high cost. The crystal amplifier is mostly a combination of transistors and integrated circuits, widely used printed circuit boards, high efficiency, stable welding quality, and high electrical performance indicators. 聽Power reserve and anti-overload capability The high-fidelity amplifier's dynamic range should be 120dB, so as to meet the needs of sound from slight to high tide, the amplifier output does not clip, so the amplifier must have sufficient power reserve. If the dynamic range of the audio voltage is 3: 1, the power dynamic range is 9: 1 because the power is proportional to the square of the voltage. In other words, the power amplifier with a power of 90W can only reach 10W to achieve high-fidelity playback. Therefore, transistor amplifiers need to have a large power reserve to prevent overload distortion. Once overloaded, the distortion almost rises vertically, which can damage the transistor in severe cases. Tube amplifiers are much more resistant to overload than transistor amplifiers. If an overload occurs, the peak of its music signal just becomes smoother than the normal waveform, and the sound cannot be heard to a great extent. For transistor amplifiers, clipping will occur at this time, and the sound quality will obviously deteriorate. This image was provided by registered user 'Technology Digital', feedback on copyright statement 聽Open-Loop Index and Transient Characteristics The open-loop index of the tube power amplifier is better than that of the transistor. It does not need to add deep negative feedback and can work stably without the phase compensation capacitor. Therefore, its dynamic index is better than the transistor power amplifier. The open-loop gain (gain before negative feedback) of a transistor power amplifier is often very large. Its excellent electro-acoustic index is achieved by adding a large amount of negative feedback. In order to suppress parasitic oscillation, the transistor power amplifier Hysteresis compensation is often used, which brings obvious transient intermodulation distortion and seriously affects sound quality. 聽Efficiency, life and cost Tube amplifiers do not have an advantage over transistor amplifiers in terms of weight, efficiency, and lifetime. The life of the electronic tube is low, and some technical indicators are obviously reduced after one to two thousand hours of use. But transistors and integrated circuits have a much longer life. In addition, tube amplifiers consume high power and often work in Class A conditions, which further reduces efficiency, but there are no harmful sound quality factors such as transient intermodulation distortion, switching distortion, and crossover distortion. In terms of cost, for the same grade of amplifier, the tube power amplifier is generally significantly higher than the transistor power amplifier. The main reasons are the high cost of electronic tubes and output transformers, and the difficulty in automating the production process of electronic tube power amplifiers, resulting in low production efficiency. This is particularly evident in developed countries. 聽Amplifier and speaker matching The output internal resistance of a transistor amplifier is often much smaller than that of a tube power amplifier. Its damping coefficient fd is very large, which can reach more than 100-200, and the maximum fd of a tube power amplifier is only 10-20. Therefore, different types of amplifiers should be used with different speakers. The speaker should be marked with fd when it leaves the factory so that people can choose it. If a speaker suitable for the damping coefficient of a tube power amplifier is connected to a transistor amplifier, the resistance of the speaker is too large, the transient response will be deteriorated, and the sound quality will be significantly reduced. Conversely, if a speaker suitable for a high damping coefficient is connected to a tube power amplifier, the sound quality will not be good due to the lack of damping. In short, the damping coefficient must be appropriate, that is, the amplifier and the speaker must be reasonably matched. 聽Sound quality Due to the above-mentioned and unmentioned reasons, the sound quality of the tube amplifier is obviously better than that of the transistor amplifier. Transistor power amplifier sounds like high frequency, mid-high frequency, but low frequency. Transistor power amplifier sounds hard, especially the low-frequency sound is not soft enough, and the high-frequency sound is sharp and dry. There is crossover distortion. These phenomena become more pronounced as the frequency increases and the volume becomes louder. However, the transistor amplifier's dynamics are large and fast, which is especially suitable for expressing more dynamic music. As for the performance of guns and lightning, of course, it is better than tube amplifiers. The sound quality of the tube amplifier is generally soft and beautiful. Specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is drizzle and clean. Human voice is its strength, and therefore more expensive. 聽Purchase considerations Since the tube amplifier can be equal to the transistor amplifier, it must have advantages. The new technology used by the transistor amplifier appears to be significantly better than the tube. So far, transistor amplifiers still have obvious advantages in the audio field, and because of their own shortcomings, they are trying to reduce and avoid these own shortcomings. For example, the increasing application of various field-effect transistors and the rapid increase of Class A amplification forms are effective measures to fight against tube amplifiers. 聽How to extend the life of tube amplifiers In use, the electronic tube must have good ventilation and heat dissipation. Overheating of the temperature will definitely shorten the life of the electronic tube, so the electronic tube should be kept as low as possible. Electron tubes are afraid of vibration, so it is also important to take anti-vibration measures to avoid vibration as much as possible. If these two points are achieved, the service life of the tube can be at least doubled. For this reason, there should be appropriate space around the tube equipment, especially above it, so as to have good convection ventilation, and if possible, use a fan to help dissipate heat. When the cathode of a tube is connected to a high-voltage power source before it reaches the required temperature, its cathode will be damaged, which will also shorten the life of the tube. Therefore, if the electronic tube equipment has a preheating device, it must be used, for example, the filament low voltage power supply is turned on to warm up first, and then the high voltage power supply is turned on. If there is no preheating device, then you should not rush in the input signal, you can turn off the volume to the minimum, wait for 20 to 30 minutes to warm up the machine before using it. If an indirect heating rectifier is used to supply the high voltage of the whole machine, it just provides a simple and effective high voltage delay. In addition, during normal use, do not switch the power frequently. Of course, if the electronic tube circuit is properly designed to avoid misuse, it can prevent the electronic tube from 'early death.' The use of thousands of listening hours for the electronic tube should be normal. The most common errors in circuit design are too high potential difference between the tube filament and the cathode, the tube screen or curtain grid voltage is applied to the maximum value, the tube filament voltage is too low or too high, and the improper installation position of the tube causes the electrode to overheat and high voltage The power supply does not have a delay device or the like.
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