Before the 1960s, the dominant audio system was always a variety of audio equipment using tube devices, and amplifiers were no exception. In the late 1960s, especially in the 1970s, it was the most unfortunate era of electron tubes. Due to its own shortcomings (large size, high power consumption, etc.), it is gradually eliminated, especially in China. In the late 1970s, electronic tubes in foreign countries began to become active again. Into the 80s, tube amplifiers became more and more popular. Especially after the invention of the high-quality sound source CD machine, with the advancement of the output transformer technology that restricts the tube amplifier, the tube amplifier can "neutralize" the hard "digital sound" of the CD player, and the position of the tube amplifier is improving. In addition, the old-aged enthusiasts have experienced their beautiful sounds in the past, and its comeback has first been welcomed by these people. At home and abroad, tube amplifiers are sometimes even a symbol of identity.
1. The electronic tube power amplifier input has a large dynamic range and a fast conversion rate.
2, the electronic tube power amplification is mostly using discrete components, manual wire, welding, low efficiency, high cost. This is especially evident in developed countries.
3. The open-loop index of the tube amp is better than that of the transistor. It does not need to add deep negative feedback. It can work stably without the phase compensation capacitor, so its dynamic index is better.
4, the sound quality of the tube amp is generally soft and pleasant, more specifically, the low-frequency sound of the tube amp is soft and clear, high-frequency sound is fine and clean and clean. The performance of vocals is their strength.
5, the high-pitched sound of the tube machine is smooth, has enough air sensation, has a considerable part of people's favorite sound dyeing, soft and slightly fuzzy sound is very beautiful.
6. The main cause of the tube amplifier is the even second harmonic. This harmonic component is very flattering, just like adding a rich harmonic to beautify the sound.
The transistor amplifier operates at low voltage and high current, and the working voltage of the power amplifier stage is within several tens of volts, and the current reaches several amps or tens of amps. The circuit design adopts the direct-coupled (OCL, BTL, etc.) output-free transformer circuit, and the output power can be made very large, up to several hundred watts, and the various electrical performances are made very high.
The tube amplifier operates at high voltage and low current. The screen voltage of the final power amplifier tube can reach 400-500V or even thousands of volts, and the current flowing through the tube is only tens of milliamperes to hundreds of milliamps. The input dynamic range is large and the conversion rate is fast.
Most of the tube amplifiers use discrete components, manual wire bonding, and welding, which are low in efficiency and high in cost. The crystal amplifiers are mostly combined with transistors and integrated circuits, widely used printed circuit boards, high efficiency, stable welding quality, and high electrical performance indicators.
2. Power reserve and overload resistance The dynamic range of the high-fidelity amplifier should be 120dB, in order to meet the needs of the sound from a slight to high peak, the amplifier output is not clipped, so the amplifier must have sufficient power reserve. If the dynamic range of the audio voltage is 3:1, since the power is proportional to the square of the voltage, its power dynamic range is 9:1. That is to say, the power amplifier with a power of 90W can only be driven to 10W to achieve high fidelity playback. Therefore, the transistor amplifier needs to have a large power reserve so that no overload distortion occurs. Once it is overloaded, its distortion almost rises to a vertical line, which can damage the transistor in severe cases. The tube amplifier is much more resistant to overload than the transistor amplifier. In the event of an overload, the peak of the music signal just becomes slippery than the normal waveform, and the sound does not sound much worse. For the transistor amplifier, clipping will occur at this time, and the sound quality will be significantly deteriorated.
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