The mysterious world of tube amplifiers

                               The mysterious world of tube amplifiers

Electronic tube amplifiers, commonly known as "amplifiers", are no strangers to audio enthusiasts. As early as the 1920s and 1930s, electronic tubes have begun to be used in audiophile equipment, from amplifiers behind the scenes of theaters to radios in folk homes. indispensable. So today we enter the world of amplifiers.

Amplifiers play an important role in the progress and sharp changes of audio equipment in the 1970s and 1980s. The advent of electronic tubes promoted the development of the wireless electronics industry, and amplifiers dominated the audio field for more than 40 years, and then gradually declined due to the advent of transistors. Although electronic tubes have been basically eliminated in other fields, the development of amplifiers has not stopped there.

In the late 1970s, tube power amplifiers became active again, and this trend became more and more popular in the 1980s, especially after the emergence of high-quality audio sources, tube amplifiers can neutralize the digital sound of these audio sources to obtain better The sense of music is also the most important reason why it can always be sought after by enthusiasts.

Then why do tube amplifiers have a warmer, softer and sweeter sound than transistor amplifiers? Let's start with a preliminary understanding of the internal structure of the amplifier.

1. The composition and principle of tube amplifier

Tube amplifiers are mainly composed of electron tubes (tubes), rectifier tubes and output transformers. The output transformer has a great influence on the indicators and hearing of the whole machine. The bandwidth of an excellent push-pull output transformer is 10Hz-100KHz. Distortion below 1% is no problem at all. The transformer has a great influence on the sound of the whole machine in terms of structure, process and material. In fact, after the transformer index 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 will be different from the traditional amplifier. Therefore, the timbre of the tube amplifier has a great relationship with the output transformer. The output transformer is an important part of evaluating a tube amplifier.

The timbre of the tube amplifier is round and warm, and the main reason for this kind of tone is that the tube amplifier can generate rich even harmonics. When the signal passes through nonlinear components, higher harmonics, especially odd harmonics, will be generated. Odd harmonics are an important cause of sound quality degradation. In contrast, the nonlinearity of the electron tube is significantly smaller than that of the transistor, so the odd harmonics generated when the signal passes through the electron tube is much less than that of the transistor. Relatively speaking, the content of the even harmonics increases, forming A mellow tone. Since the amplification characteristic curve of the field effect tube is relatively flat, the power amplifier installed with the field effect tube has the charm of a tube amplifier.

Another reason for the timbre of the tube amplifier is the use of inductive components in the signal path of the tube amplifier - the output transformer. The inductive element has two functions: 1. It has a delay attenuation effect on high-frequency signals. The higher the signal frequency, the more obvious the delay attenuation effect. This kind of intermediate frequency signal is more prominent, resulting in a "dark and warm" tone. In addition, the frequency of the odd harmonics in the signal is generally higher than that of the even harmonics. After the delay attenuation, the proportion of the even harmonics is relatively increased. Second, the peak signal in the signal is clipped, resulting in a soft tone.

In fact, in the analog sound source, the magnetic head of the deck and the moving magnetic head of the LP record player are all inductive components, so the timbre of these two sound sources is relatively warm and soft. The tube amplifier uses an output transformer, and the tone becomes warm and soft.

2. How the amplifier works

In the final stage of the amplifier, there are single-ended and push-pull working methods. It is easier to obtain high power by using the push-pull method, so it is a very common circuit form, but because the push-pull working method is a superposition method , so objectively there is some distortion, and there are additions and subtractions in the push-pull superposition, and in this addition and subtraction, some small things that were not there before may be added, and some small things that were originally there may be subtracted at the same time.

However, if a single tube is used in the final circuit to work in a single-ended Class A state, there will be no unavoidable problems in the push-pull working mode. Therefore, the single-ended one is much better than the push-pull one in terms of hearing, especially in some tiny details. However, it is difficult to increase the power of a single-ended one. For example, with the same type of tube, it can only achieve 8W when single-ended, but it is easy to achieve 30W when it is push-pull. If you want to make it bigger, you have to pay some price for the sense of hearing. At the same time, in terms of technology, 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.

3. The difference between the different connection methods of the electronic tube in the push-pull circuit

In the final push-pull circuit, the electron tubes are usually tetrodes and pentodes, so the connection methods used are divided into three types: three-stage tube connection method, super-linear connection method and standard connection method.

Theoretically speaking, the triode connection method has the smallest distortion and the smallest output power; the standard connection method has relatively larger distortion and the largest power; the super-linear connection method is between the two. Each has its own advantages and disadvantages in the sense of hearing, relatively speaking, the triode connection method is slightly better. But the triode connection method has a disadvantage, it will reduce the life of the electron tube, so it is rarely used in industrial production.

Four: the life of tube amplifier

Many people think that the service life of tube amplifiers is much shorter than that of transistor machines, and this judgment is too subjective. In fact, it is not the case. In principle, the life of tube amplifiers is semi-permanent. The life of the electronic tube depends on the electronic tube. The theoretical life of the electronic tube is not too long. Generally speaking, it is only thousands of hours, but it is also common for good electronic tubes to be used for tens of thousands of hours. For example, the picture tube of a TV is a special electronic tube. Of course, the lifespan of many audio tubes cannot be compared with that of a picture tube.

Generally speaking, the electronic tubes used in audio have transportation failure and early failure. The failure can be found within 1-2 months after use, or found in the factory production. For electronic tubes with relatively stable quality, it is not a big problem to use them for 2-3 hours a day and 2-3 years. Even if the bile duct is broken , you only need to change the gallbladder again, and you can enjoy the soft and beautiful music with new vitality.

Compared with crystal amplifiers, amplifiers have a higher overload capacity. Crystal amplifiers may be damaged within one-thousandth of a second when they encounter some failures, while tube amplifiers can not be damaged within minutes. Therefore, you don't have to worry about the life of the amplifier.

5. Maintenance and precautions of amplifier

As mentioned just now, the service life of the amplifier is semi-permanent in principle, but the premise requires a good method of use. Any equipment, if there is no good method of use, then the service life will be greatly reduced. Let me introduce the tube amplifier for you. Some maintenance and precautions:

1. Connect the load (speaker) before turning on the power. Do not send signals without connecting the load after turning on the power, so as not to burn out the output transformer.

2. The power supply should not be too high or too low. The power supply voltage should be within 5% of the specified voltage. If the mains power often exceeds this voltage value, it is best to use an AC regulated power supply.

3. The temperature of the tube amplifier is high when it is working, so pay attention to ventilation and heat dissipation when placing it.

4. Do not spill liquid on the electronic tube during startup or just after shutdown (within 30 minutes), so as not to burst the electronic tube.

As long as you pay attention to the above points during use, the amplifier can work stably.

6. Comparison of tube amplifiers at home and abroad and collocation of speakers

The tube amplifier in our country started much later than that of foreign countries, and the tube amplifier itself is also a representative product of the times integrating culture, craftsmanship and technology. Although there is a certain gap between domestically produced tube amplifiers and some famous foreign tube amplifiers, after years of continuous efforts, this gap is gradually narrowing. After years of precipitation, domestic excellent tube amplifiers are much better than foreign brand tube tube amplifiers, and the price advantage makes domestic excellent tube amplifiers cost-effective and also increases their competitiveness.

Written by : Davecl Audio

The Audio Equipments Manufacturer 

Welcome OEM or ODM

#ceilingspeaker #wallspeaker #inceilingspeaker #inwallspeaker
#hifisystem #hifaudio #homeaudio #hometheater #loudspeaker #poweramplifier #stereo #cdplayer #audiopro #swedishdesign #scandinavian #bluetoothspeaker #airplay #googlecast #spotify
#wifispeaker #wifimultiroom #multiroomspeaker #multiroomaudio #speakerlife #audiophiles #hififanatics #audiosetup #audiofactory #audiomanufacturer