For the comparison between the amplifier and the crystal, only the following two issues are discussed here, namely, the price-performance ratio and the sound quality characteristics. The price is less than 1,000 yuan (per unit). Because the amplifier cannot be produced at this price, people cannot use it. You can buy a good amplifier product at this price. Although you can buy a crystal machine at this price, it is difficult to buy a good product. In terms of sound quality, in general, amplifiers of the same price below 30,000 yuan, the sound quality of the amplifier is usually better than the crystal machine; in the price range of 30,000 to 5 million yuan, each has its own merits; above 5 million yuan, the crystal machine generally has a relative advantage At this time, the crystal machine is excellent in all aspects, and the amplifier is characterized by characteristics; crystal machines below the price of Wuyuan are generally superior to the amplifier in terms of bass strength, speed, and brightness of treble. The sound quality, timbre, musicality, and hearing resistance are difficult to compare with the amplifier. This is the common understanding and experience of many people.
2. About foreign and domestic tube amplifiers
The start and history of foreign tube amplifiers far surpass that of China. Besides, the amplifier product itself has a certain artistic and strong cultural background, which is reflected in the adjustment of the product's voice, brand positioning, market strategy, appearance design, product quality stability, etc., it should be said that Compared with some excellent foreign brands, we are far away from them in some respects in some aspects; but after efforts in recent years, this distance is shrinking. Compared with some foreign brands, some of our better products are definitely stronger than them, and we have a great advantage in price. On the same level of products, our prices are at least 1 / 2--1 / 5 or more lower than imported machines. At present, our individual products are even better than the sound quality and timbre of some famous brand products abroad at a lower price. This is no strange thing. The direction of our domestic product efforts is to establish brand awareness and strengthen product quality and artistic standards.
3. About the shape (shape) of the amplifier
Most of the appearance of the tube amplifier is to put the electronic tube (bladder), these components of the transformer are exposed outside the casing, which is different from the box machine in the traditional concept of people. Does the amplifier have to do this instead of being box-shaped? No, in fact, some of the amplifier products have been made into box-type machines, so why are "bare" machines popular at home and abroad? This is related to the psychological aesthetic concepts of designers and users. The design of modern tube amplifiers is like industrial art design, which pays attention to fluctuations, color contrasts, bright lines, and the embodiment of materials. The shape and processing of an exquisite tube machine are just like a piece of art. The box-type machine is more difficult to reflect in these aspects, and the free space of the bare machine is mostly. In addition, after the tube is working, the filament of the tube is lit to give people a warm feeling, and compared with the box-type machine, it looks colder. There is no "human touch" like the "bare metal". This is a bare-metal machine. One of the reasons for its popularity. In addition, the bare metal can better reflect the characteristics of the amplifier. Although the bare machine is often not as convenient as the box machine in use, it is more difficult to "wait", so there is a situation where the bare machine and the box machine coexist. From a proportional point of view, the amount of bare machines is greater than the amount of box machines.
Fourth, the technical indicators and standards on the amplifier
Frankly speaking, except for the static intermodulation distortion, which is comparable to the crystal machine, the technical indicators of the amplifier are not as good as the crystal machine. In fact, the survival and development of the amplifier is not because of its technical indicators. Pay attention to technical indicators, the amplifier has no market. In fact, electro-acoustic technology is still very imperfect so far. The existing technical indicators can only explain the problem from one aspect, but they cannot reflect the problem in essence. For example, the measurement of existing amplifier specifications is measured under the assumption that the load is a purely resistive (linear) load, while the actual load is a complex resistive (non-linear) load. Another example is that the measurement of the speaker is measured at a power of 1W at a distance of 1W, and the actual listening can not be under the condition of 1M / 1W, so such a measurement index can only be used as a reference, not as a criterion for selecting an amplifier . It can be said that a product with good technical indicators may have a bad sense of hearing, while a product with a good listening indicator may have only mediocre technical indicators (of course it will not be bad).
For a mass-produced electronic product to ensure its uniformity and consistency, it must have a corresponding production standard (technical documents, production process documents and inspection documents), which is already common in some more formal product production. Things, but these standards are only used to guide the production and ensure the consistency and uniformity of product quality, and have no other significance. The production standards of an enterprise are only useful for the specific products of the enterprise, but are not useful for other enterprises. The sound quality of the sound is meaningless. To be precise, there is no standard to measure art. In reality, the higher the level of audio products, the less stringent the production standards.
Fifth, some technical problems in the tube amplifier
1) About single-ended and push-pull
In the final stage of the amplifier, there are push-pull working methods and single-ended working methods. Because the push-pull method is easier to obtain high power, it is a very common circuit form, but because of the push-pull working method It is a superposition method, so there is some distortion objectively, and there is addition and subtraction in push-pull superposition. In this addition and subtraction, some small things that are not originally can be added, and some of the original ones are subtracted. Small things. If a single tube is used in the single-ended Class A state in the final circuit, there is no problem that cannot be avoided by the push-pull operation. Therefore, the single-ended sound is much better than the push-pull, especially in some small details. However, it is difficult for a single-end to do a lot of power. For example, using the same type of tube, it can only achieve 10W when it is single-ended, and it is easy to achieve 30W when it is push-pull. At the same time, in the process, the single-ended machine is more difficult to handle than the push-pull machine. Therefore, single-ended circuits are often used in high-end machines, and push-pull circuits are used in popular machines.
2) The difference of the different connection methods of the tube in the final push-pull circuit
The tubes used in the final push-pull circuit are often quadrupole and pentode, so when using these tubes, there are three-stage tube connection method, super linear connection method and standard connection method. The difference between them is theoretically speaking, the triode connection method has the least distortion and the smallest output power; the standard connection method has relatively large distortion and the largest power; the ultra-linear connection method is somewhere in between. The sense of hearing is different, and the triode connection method is relatively better. However, the triode connection method is rarely used in industrial production due to the loss of the life of the electron tube.
3) The influence of the driving circuit on the sound quality and timbre
Generally speaking, the driving circuit and structure have a great effect on the orientation of the sound quality and timbre. In the low-frequency strength of the sound, the sense of speed in the middle and high frequencies and the sense of density in the middle frequency can achieve different effects by pushing the circuit differently. There are many kinds of driving circuits, and it is difficult to judge the quality of the product from the difference between the driving circuits. What kind of circuit to choose is a designer's choice of tone orientation.
4) The effect of different types of tubes on sound
The commonly used electron tubes of the front stage push circuit are ELF82, 6F1, EF86, 12AX7, 12AU7, 12AT7, 12BH7, 6DJ8, 6SN7, 6SL7, 6SJ7, 6N1, 6N2, 6N3, 6N6 and so on. In principle, these tubes can make a good sound when used in amplifiers, but each model has its own characteristics. Designers will decide which model to choose based on many factors. Generally speaking, ELF82, 6F1, EF86, 12AX7 , 12AU7, 12AT7, 12BH7, 6DJ8, 6SN7, 6SL7, 6SJ7 are the most commonly used electronic tubes in audio abroad, and many manufacturers have produced them, so the interchangeability is better, so export machines or foreign machines are commonly used. The commonly used electron tubes in the final circuit are: KT88, 6550, EL34, 6L6GC, 2A3, 300B, 211, 845. The first four types of electron tubes are side-heated quadrupoles or pentodes, which are often used in push-pull circuits with higher power. The last four tubes are direct-heating triodes, which are mostly used in single-ended Class A (2A3, 300B are also often used in push-pull circuits). Relatively speaking, the sound of the direct-heating triode is slightly better than that of the side-heating quadrupole and pentode. But it is also a triode or a quadrupole, but the sound quality of each model has some differences and characteristics. Because the amplifier is a plug-in device, it is convenient for direct replacement, so changing the amplifier to play a game has become a great fun in the use of the amplifier.
5) Influence of output transformer on timbre
The output transformer has a great influence on the index and the sense of hearing of the whole machine. The bandwidth of the excellent output transformer for push-pull is 10Hz-100KHz, and the distortion is less than 1%. It can be said that the transformer is no longer a key component that affects the indicators of the amplifier. However, the structure, process and materials of the transformer have a great influence on the sound of the whole machine. In fact, after the index of the transformer exceeds a certain range, the higher the index is not necessarily the better. If the amplifier does not have an output transformer, such as OTL, its sense of hearing is different from the traditional amplifier. Therefore, the timbre of the amplifier has a great relationship with the output transformer.
6) About the combined amplifier and front and rear amplifiers
The combined amplifier has the following characteristics: 1. When the signal source is at a certain input level, the output of the amplifier can reach full power; 2. The amplifier has multiple sets of source input options; 3. The amplifier has a level control function; 4. The left and right channels are combined into one, and high and low tone control devices can also be provided. In the early days, the output level of the signal source was relatively low, generally around 0.2V, so the input level of the combined amplifier should be below 0.2V, and the modern signal source has changed a lot. If the CD player has been widely used, the output level of modern signal sources averages between 0.5-1V, so the input sensitivity requirements of modern amplifiers also change accordingly. Of course, no matter how it changes, as long as the first three of the combined amplifier are met, it is a combined amplifier. The front and rear amplifiers are the three parts of 1 source selection, 2 level control and 3 voltage amplification. (The third item is the active pre-stage and the third item is the passive pre-stage). Voltage amplification and power amplification are integrated (or two bodies) with left and right input, no level control and source selection (input level is between 1-2V), this method can be used in structure, distribution, and use The material is more reasonable, so the front and rear split amplifiers are higher than the combined ones, and the price may be much higher.
Six, about the service life of the amplifier
In principle, the life of the amplifier is semi-permanent. Compared with the crystal machine, the relative life of the amplifier is determined by the electron tube. The theoretical life of the electron tube is not too long. Generally speaking, it is only a few thousand hours, but a good electron tube is used. Tens of thousands of hours are also very common. For example, the picture tube of a television is a special electron tube. Of course, many audio tubes cannot be compared with the life of kinescopes. Generally speaking, there are transportation failures and early failures for audio tubes. The failure can be found within 1-2 months after use, or found in factory production. For a stable quality electron tube, it should be used for 2-3 hours a day. It should not be a problem to use it for 2-3 years. It is not expensive and not difficult to buy. With good after-sales service, the service life of the bile machine should not be a problem. After the bile machine is replaced, it can renew its vitality, just like the new one. In fact, many antique gallbladders are still sold at high prices in the market. Doesn't it explain the lifespan of the bile machine from the other side? Adding the bile machine to the crystal machine has a stronger overload capacity. When the crystal machine encounters some failure It may be damaged in one-thousandth of a second and the amplifier can be left untouched for a few minutes.
7. Notes on using the amplifier
1. Connect the load (speaker) before turning on the power. Never turn on the power and send a signal without connecting the load, or the load is short-circuited.
2. The power supply should not be too high or too low. The power supply voltage should be within 5% of the specified voltage. It is best to use an AC stabilized power supply when the commercial power supply frequently exceeds this voltage value.
3. When the tube is working, the temperature is high, pay attention to ventilation and heat dissipation.
4. Do not spill liquid on the electronic tube during startup or just after shutdown (within 30 minutes).
In general, pay attention to the above problems in use, the tube is able to work *.
8. Matching of amplifier and audio-visual equipment
It is very important to use a speaker to match what kind of speakers, but it is difficult to find a matching principle. Generally speaking, it is best to match European and American speakers with a sensitivity of over 87db such as British boxes and Italy. For example, HARBETH, ROGERS, SPENDOR, PROAC, B & W, KEF, TANNOY, TDL, EPOS, MISSION, France, JMLAB, Italy, CHARIO, SOUNS FABER. PROACTABELETTEIII also has some high-powered horn boxes such as: ALTLC, KLIPSCH, WESTLAKE, etc. It also has a special charm with a low-power single-tube type A tube amplifier. Some models of "Voice of Beauty" and "Small Tornado" are available for domestic boxes. In the case of inexperience, you can find some examples of the existing collocation or the actual collocation and listen to it before confirming.
Nine to extend the life of gallbladder
The accelerated loss of the lamp bulb is mostly caused by the loss of the filament and cathode. With regard to the filament, cold start (that is, not to gradually pressurize the filament) accelerates the loss of the filament, especially the use of AC ignition filament. Take 6l6gc as an example, the filament generally consumes 66.3v0.9a, but the inrush current reaches 3a at the moment of startup. As for the boldness, because modern models generally use high-voltage commutator, high voltage in the whole Han Dynasty, there is inrush current when starting up, because the high voltage is immediately applied to the screen when starting up, but the cathode has not been preheated enough, the screen has appeared Flow, because the cathode emits electrons * a layer of metal oxide coated on the cathode metal cylinder has a considerable temperature. When the operating temperature is not reached, the resistivity of each part is different due to the lack of heat penetration. It is concentrated in the area where the resistance is small and damaged. The same is true when the power is turned off. After the power is turned off, the cathode temperature drops, and the capacity of the high-voltage filter capacitor is generally large. The high voltage will be stored for a period of time. The screen current maintained during this time also accelerates the loss of the cathode.
Therefore, the following methods may be considered for improvement:
1. Lamp rectification, this is the rectification method used by radio amplifiers in the 1950s and 1960s. This requires that the power flow hydrocarbon compressor have another 5V and standby power consumption. After the rectification, the high voltage can be fully applied to the screen electrode within ten seconds, and the cathode has sufficient time to warm up, so as not to accelerate the lamp consumption. However, the disadvantage is that the internal resistance of the high-voltage power supply is increased by the rectification of the lamp bulb. For the signal source, the voltage will be reduced and the gain will be reduced. The general effect is to slow down the transient and the sound floor is slow. The solution can be considered parallel rectifier to reduce the internal resistance of the power supply.
2. Install high-voltage switch, see Figure 5. For some factory machines, two standby and working switches are provided. The principle is to turn on the filament switch first, and then turn on the high-voltage switch after a certain time. Such as adding switches and parallel resistors to the high voltage secondary. s1 parallel connection resistance and series resistance in the future, it is expected that there will be a certain degree of voltage reduction during the preheating time after booting, to eliminate the phenomenon of accelerated bile loss due to inrush current. In terms of high voltage, s2 can be connected after s1 is connected, so that the cathode has enough warm-up time before adding full-scale screen pressure.
3. A delay circuit can also be used, so that the filament and high voltage can be gradually increased, which has the purpose of protecting the lamp. However, the circuit is more complicated, and I do not know the degree of impact on the sound quality. It requires higher production knowledge and technology, so It may not be suitable for ordinary people.
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