What is the difference between tube power amplifier

by:Gisen     2020-06-11
Advantages of tube power amplifier 1. The input dynamic range of the tube power amplifier is large, and the conversion rate is fast. 2. The vacuum tube power amplifier mostly uses discrete components, manual wire bonding and welding, which has low efficiency and high cost. This is particularly evident in developed countries. 3. 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 adding phase compensation capacitors, so its dynamic index is better. 4. The sound quality of the tube amplifier is soft and beautiful overall. More specifically, the low frequency sound of the tube amplifier is soft and clear, and the high frequency sound is delicate and clean. Representing human voice is its strength. 5. The treble of the tube machine is relatively smooth, with sufficient sense of air, and has a kind of sound staining that quite a few people like. The soft and slightly fuzzy sound is very beautiful. 6. The tube amplifier is mainly caused by the even-numbered second harmonic. This harmonic component is very flattering, just like adding a rich overtone and beautifying the sound. Disadvantages of tube power amplifier 1. The service life of the electronic tube is low, and some technical indicators have dropped significantly after using for one or two thousand hours. 2. The tube amplifier consumes high power and often works in the Class A state, which reduces the efficiency, but there are basically no harmful sound quality factors such as transient intermodulation distortion, switching distortion and crossover distortion. 3. The tube amplifier is not superior to the transistor amplifier in terms of weight, efficiency, and life. 4. In use, the electron tube must have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the electron tube, so the electron tube should be kept as low as possible. 5. The electronic tube is afraid of vibration, so it is also important to take anti-vibration measures to avoid vibration as much as possible. ? Use the extension of the life of the tube amplifier In use, the electron tube must have good ventilation and heat dissipation, and the overheating of the temperature will inevitably shorten the life of the electron tube, so the electron tube should be kept as low as possible. The electronic tube is 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 electron tube can be at least doubled. To this end, there should be a proper space around the tube equipment, especially above it, so as to have good convection ventilation, and if possible, a fan can be used to help dissipate heat. When the cathode of the electron tube has not reached the required temperature, that is, a high-voltage power supply is added, its cathode will be damaged, and the life of the electron tube will also be shortened. Therefore, if the tube equipment has a preheating device, it must be used. For example, first turn on the filament low-voltage power supply to preheat, and then turn on the high-voltage power supply. If there is no preheating device, then don't rush to connect the input signal, you can turn off the volume to the minimum, wait for 20 to 30 minutes to turn on the machine and use it. If the bypass 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 you design the tube circuit correctly and avoid misuse, you can prevent the tube from 'early death'. It is normal for the tube to use thousands of listening hours. The most common errors in circuit design are the potential difference between the tube filament and the cathode is too high, the tube screen or curtain grid voltage is used 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 The power supply has no delay device, etc. Power amplifier performance index The main performance indicators of the power amplifier are output power, frequency response, distortion, signal-to-noise ratio, output impedance, damping coefficient, etc. Output Power Output power: The unit is W. Since the measurement methods of different manufacturers are different, there are some names with different names. For example, rated output power, maximum output power, music output power, peak music output power. Music power Music power: refers to the instantaneous maximum output power of the power amplifier to the music signal under the condition that the output distortion does not exceed the specified value. Peak power Peak power: refers to the maximum music power that the power amplifier can output when the volume of the power amplifier is adjusted to the maximum without distortion. Rated output power Rated output power: the average output power when the harmonic distortion is 10%. Also known as the maximum useful power. Generally speaking, the peak power is greater than the music power, and the music power is greater than the rated power. Generally speaking, the peak power is 5-8 times the rated power. Frequency response Frequency response: indicates the frequency range of the power amplifier and the unevenness within the frequency range. The straightness of the frequency response curve is generally expressed in decibels (db). The frequency response of household HI-FI amplifiers is generally 20Hz--20KHZ plus or minus 1db. The wider the range, the better. The frequency response of some of the best power amplifiers has been achieved 0--100KHZ. Distortion Distortion: The ideal power amplifier should amplify the input signal and restore it faithfully without change. However, due to various reasons, the signal amplified by the power amplifier is often compared with the input signal to produce different degrees of distortion. This distortion is distortion. Expressed as a percentage, the smaller the value, the better. The total distortion of the HI-FI amplifier is between 0.03% and 0.05%. The distortion of the power amplifier includes harmonic distortion, intermodulation distortion, crossover distortion, clipping distortion, transient distortion, transient intermodulation distortion, etc. Signal to noise ratio Signal-to-noise ratio: refers to the ratio of the signal level to various noise levels output by the power amplifier. Expressed in db, the larger the value, the better. The signal-to-noise ratio of general household HI-FI amplifiers is above 60db. Output impedance Output impedance: The equivalent internal resistance presented to the speaker is called the output impedance. A good performance index of a power amplifier does not necessarily prove that it has a good tone, which must be recognized by first-time fans. This is what many audiophiles are struggling to explore. ? Amplifier characteristics 1. Maximum output power As the power amplifier should provide enough power to the load, the working voltage and working current of the power amplifier tube are close to the limit value under the premise of safe operation, that is, the tube works at the limit value state. 2. The highest possible power conversion efficiency The output power of the power amplifier is derived from the DC power of the DC power supply through the transistor. During the conversion, the power tube and the energy-consuming components in the circuit both consume power. P0 represents the power obtained by the load. PE represents the total power provided by the DC power supply, η represents the conversion efficiency, then η = (Po / PE) * 100%, and the size of η reflects the utilization rate of the power supply. For example, the efficiency of an amplifier η = 50%, indicating that only half of the DC power provided by the power supply is converted into output power and passed to the load, and the other half is consumed inside the circuit. This part of the energy causes the temperature of the tubes and components to increase. Will burn out the transistor. Pay attention to the heat dissipation problem of the power amplifier tube. In order to ensure the safe operation of the power tube, a heat sink is generally added to the high power tube. How to improve efficiency and reduce power consumption is an important issue for power amplifiers. 3. The allowed nonlinear distortion power amplifier tube working in large signal state inevitably produces nonlinear distortion. The greater the output power of the same power amplifier tube, the more serious its nonlinear distortion. The requirements for the nonlinear distortion of the power amplifier are different in different occasions. In the measurement system and electroacoustic equipment, the nonlinear distortion must be limited to the allowable range, and the nonlinear distortion is reduced to the secondary in the driving motor or control relay contradiction. In addition, the analysis of power amplifiers can only use the graphical method, and the micro-variable equivalent circuit method is no longer applicable. In order to obtain greater power and efficiency, the power amplifier and the load must be matched. The traditional power amplifier and the load are coupled by a transformer. The advantage of this type of power amplifier is that it is easy to achieve impedance matching and large output power. The transformer is large, bulky, and has poor frequency characteristics, and is not conducive to integration. It is rarely used in power amplifiers now produced, and is gradually replaced by complementary symmetrical power amplifiers. The complementary symmetrical circuit eliminates the bulky transformer, and has the advantages of simple circuit structure, high efficiency, good frequency response, and easy integration. There are two forms of complementary symmetrical power amplifiers: one uses a single power supply and a large-capacity capacitor to couple with the load, called the OTL circuit; and one uses a dual power supply and requires a capacitor to directly couple the complementary symmetrical power amplifier, called the OCL circuit. The difference between tube amplifier and ordinary amplifier 1. The production materials are different. The former uses electron tubes and the latter uses semiconductor transistors. 2. Tone: The former has a wide dynamic range, which makes the tone thick. The dynamic range of different power amplifiers in the latter varies greatly, and some sounds are thin. 3. Volume: The former is large and the latter is small. 4. Efficiency: The former has low efficiency and consumes electricity due to the fact that the filament heats up the electrons to excite the electrons. The latter is highly efficient and saves electricity. 5. Lifespan: The life of the former tube is measured in thousands of hours, and the life of the latter is tens of thousands.
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