Zheng Yuanlin "Audio Technology" 2000-09
In public, we can often see some chasing stars or music fans to listen to music. They wear headphones in the noisy environment, and they are self-reliant into music. But you know that there is a class of more professional headphones in the fever world. They have a variety of headphones such as German Senhe Sel 580, Akg K141 and 240, Germany, and more. This type of earphone is mostly designed for professional recording, so technical indicators are very good, wide, straight, dynamic is extremely grand, very low distortion, thus can be particularly accurate, objectively play a variety of music signals. In addition, the headphones are not affected by the box, diaphragm mass, frequency division, phase, positioning and other factors, and overcome the interference of the external factors. This has got a recognition of music and sound circles as compared with the sound quality.
However, such professional earphone impedance is generally high (300Ω-600Ω), although the power amplifier is provided with a headphone output socket, most is a simple connection to the power amplifier output terminal and the headphone socket through a 30,000Ω resistor. This is In order to prevent excessive voltages from amplifier output to avoid overload, the load effect produced by this 300ΩL resistance will make the sound become cloudy, and the sound quality is seriously deteriorated. The general CD machine's headphone output, most manufacturers use a single op amp to design a very simple output circuit, which is unacceptable to sound quality first enthusiasts. Therefore, in order to meet the requirements of high impedance and high-pushing voltage, the only solution is to design a dedicated headphone amplifier. This earphone amplifier introduced in this paper can be successful in order to make the beginner can be successful, so the circuit design is extremely simple, eliminating the cumbersome debugging, is a very good OTL electronic tube headphone amplifier. Someone is to ask why use tubes? Because it has the following advantages: (1) The electron pipeline is excellent, stable, high working voltage, large output amplitude, and it is difficult to generate clipping. (2) The work is stable, since the electronic tube is working in the filament heating, the internal operating temperature of the tube is usually above 400 ° C, the temperature of the natural ambient temperature is far from the temperature of the bile duct, no matter the spring and summer autumn and winter dose work is stable. Not affected by the ambient temperature. Therefore, such as constant current, regulator, protection can do not, this is in line with the principle of high fidelity - concise first.
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The specific circuit is: the first level is selected for the SRPP, which is parallel to the push-pull amplification circuit. The advantage of the circuit is that the input impedance is high, the output impedance is low, the circuit is small, the frequency is straight, the maximum feature is the distortion rate Elevation and decrease. Two triodes V1, V2 for voltage amplifying are powered by a series DC, and each tube is responsive to half of the power supply voltage, but for the AC signal, it is parallel, and the screen of the upper tube is an AC potential, and its input signal is taken from below The pipe of the tube, the upper tube is output from the cathode, so that these two pipes become parallel work. Because of the use of 12AU7 electronic pipe, it enters the range wide, the magnification is moderate, and the cross guide is not high, so it is particularly suitable for the source of the mainstream of CD, and takes into account the music and fidelity, and it is more suitable for open loop circuit. Used, because the circuit has no large loop negative feedback, only local negative feedback of the pipe itself, so the circuit is relatively stable, and there is no signal phase shift. Linear and transients are ideal. The second stage is the 6n6 double triode parallel cellar follower, which is directly coupled to the first level output, which has a good match, which minus the components, while reducing the container brought by coupling capacitors. The end-level output is a cathode coupling circuit, and the circuit design is simple, it is easy to adjust, although it is uns, but the performance is excellent. This OTL cathode output circuit has canceled the blockbox, audio output transformer that has been plaguing the electronic pipe power amplifier, thus widaking the frequency response, reducing the phase shift, reducing distortion, increasing analytics. The electronic tube headphone amplifier can also switch the output signal to the line output via a double-knife switch, which is also a very good tube pre-tube predecessor amplifier to upgrade your audio equipment, one-purpose use.
The quality of the power is definitely not ignored, as the electronic pipe audio power amplifier is actually an audio signal transducer. It is best to use EI type. Although such a core is smashed in a ring, the R-type core leaks magnetic, but the experiment proves that this core is the most sound. I use a 150WE1-type Japanese imported high silicon core, a tongue width of 35mm, a stack of 52mm, a primary φ0.62 enamel wire around 660, the secondary high pressure φ0.38 enamel wrap around 690, the filament with φ1.3 enamel wire 20, between the primary and secondary must add static isolation layer, and the power cord uses a thick three-core guardline. Electronic tube headphone amplifier enclosure must be firm and connected, and amateur production should also be in line with national electricity standards, while improving the improvement of the whole machine. High voltage power supply supplies a smooth high voltage power supply to headphone amplifier using a transistor bridge rectification, and then a slightly smoothing filter consisting of a blocking ring and an electrolytic capacitance. The electrolytic capacitor can be used in parallel with a CBB capacitor in parallel with a good laden card, which can improve the medium treble analytical force in the "+" "-". The tube filament is supplied with a transistor bridge rectification via a capacitive filter, and a 50 kΩ resistor is connected to a high voltage circuit of around 160V, so that the wire potential is improved, so the purpose of this is to improve the whole machine signal to noise ratio, and the second is to reduce the filament The voltage between the exterior is protected from the tube to avoid being broken. After these rigorous measures, the signal-to-noise ratio of the electronic tube headphone amplifier is particularly high. When the cut signal source opens the volume potentiometer to the maximum, the slightegate sound is not heard.
With a simple line, choose the above components, you can make a solid foundation for the production of headphones. 12AU7 can choose Changsha dawn, or you can choose from Japanese goods, of course, it is the best in Western Europe, especially the MU11ARD ECC82 its voice is the most smooth. 6N6 can be selected from Beijing, 6N6J or 6N6T, and there is a conditional optional E182CC. The 6N6 screen is extremely long, the cathode emission is large, because the screen is extremely current, because it is designed for the cathode output, so it promotes strong ability. The resistance can be used in the electrical membrane resistance, and the metal film resistance of the domestic large robe can also be used, but the power must have a balance because the 6N6 cathode output current is large (double tube up to 50 MA) cathode potentials up to 150V, this resistance should be selected 15W-20W resistance, but the wire is electrically resistant, affecting the sound quality, so it consists of 10 2W 27kΩ resistors, which can be welded to a homemade circuit board. Output coupling capacitors are components that are related to music quality. They must use the superior products, and there is a conditional use of supplements, but also the CBB capacitance, capacitive pressure, to protect headphones.
There are two kinds of enclosures, one is a fully enclosed type, modified with an old OK amplifier, and the other is half-naked, tube and transformer blocking circles, which look very nice, material can be copper, aluminum plate, Stainless steel or iron plates, special attention is taken by iron plates, as the iron plate belongs to a magnetine material, and the transformer core and the chassis must have a certain distance, or some of the pads on the pad. Listen: Group 1: Marsshi 63SE Homemade Electronic Tube Headset Amplifier Line Output Transistor Post Speaker Du Xi 2.1 Use this electronic tube headphone amplifier line output to switch the original transistor front stage, first feel that dynamics increase, bass become elastic The medium is sweet and round, the treble is fine, and it seems to be more resistant to the past. Group 2: Marant 63SE Homemade Electronic Tube Headphones Amplifier Line Output 813 Unit Amplifier Speaker Du Xi 2.3 Use this electronic tube headphone amplifier line output to switch the original 6N8P timid stage, first feel that the analytical force is increased, and the music signal is more Many details, the sound is thick, warming, sweeter, the voice is very kind, it is really tired, do not want to shut down. According to the analysis, the original daring stage has 6N6 cathode output, so the output impedance is still low, and the impedance is reduced to 50 Ω after increasing the 6n6 cathode output, and the 6N6 current is large, and the zoom signal is very calm. Later, I saw a magazine report: "Some brand-name CD functions output high-level signals, and can do not need pre-stage and direct power amplifiers, these CD machine output impedances can generally do about 50Ω. It seems that the electronic pipe amplifier has 20 The role of decibel gain and relatively low output impedance is unleurvened in the entire sound system. The last electronic tube headphone amplifier uses German Senhe Sel HD580 audition, the sound is warm, the sound quality is beautiful, the treble is smooth, the spin Plenty of thickness, the bass is relaxed, soft and soft, spend more than 2,000 yuan to buy headphones, then make an electronic tube headphone amplifier, you can enjoy the effect of three and 40,000 yuan audio equipment, this is your most super The choice of value, then you can wear the headset, open your hard work, connect the source, you can enjoy the beautiful, beautiful music.
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