Construction 25W single-ended Class A tube amp circuit diagram EL156
Danji mellow, transparent, natural sound, sweet, sincere, tireless listening to long, full of humane color. In building a harmonious and beautiful life, tube amps have become a
udiophile companion, it is becoming a trend. In the tube amp, especially single-ended Class A tube amp sound best. In 300B, 845 single-ended Class A tube amp bile constituted Danji become the best, the most beautiful sound, people who heard did not forget. However, single-ended Class A tube amp 300B formed but fly in the ointment, the output power is generally only 6.5W, more than listening to the usual 20m2 space for small power. 845 single-ended Class A tube amp bile output power constituted around 20W, listening to meet the requirements. Only 845 belong to the high-pressure duct, operating voltage 1200V need more, not only high production costs, production Shihai less secure, the volume is also larger. So, is there a gall bladder, output up to 20W or more, small size, suitable for building a home Danji it Western Europe gallbladder EL156 worthy of this task. For ELl56 gall many people do not know. Its no wonder, ELl56 was developed in 1968, regarded as the younger generation in the family of gall. 1960s is the peak age gall development, then began to decline. By the 1970s, foreign transistor has entered the electronics industry, replaced the tube. Thus, although the latest ELl56 as outstanding bravery been developed, but has not yet had time to use it is widely used in the transistor tide flooded, so anonymity, less well known. ELl56 developed by the famous German community bile Telefunken (Telefunken) company production. The company produced audio with bile workmanship, elegant, sweet sound balance, pure and delicate, can be described as the best in the gall bladder, and the United Kingdom Mullard (Mullard) side by side, called the Western European brand. Unfortunately, Telefunken company will also shut down the production line in the bile duct transistor popular tide. ELl56 has long been discontinued. Fortunately, the dawn of our tube factory in accordance with the original data, in turn ELl56 re-development, and become the sole manufacturer of the tube. According to the factory to speak, ELl56 exported to Japan each year, it has become the new love of Japanese gall fans. ELl56 based oxide cathode lamps, and therefore has a higher cathode emission current and low operating voltage. The tubes screen up to consuming 50W, stronger than the KT88 power bile also higher than 10W. Im afraid ELl56 regarded as indirectly heated cathode bile king. Compared with the 845 direct thermal lamps, low power filament ELl56 2/3 pole screen operating voltage of only its l/3, is a single-ended output power up to 25W, the superior performance of the people gasp in admiration. True-called latecomers. First, the circuit works The drawings are using A23I.156T tube amp circuit ELl56 bile composition. This machine is a two-channel stereo amplifier, the figure shows only one channel amplifier, the other channels are identical. As can be seen from the figure, the machine uses two-stage amplification. Preamp with ECF80 (domestic model 6F1), with ELl56 amplifier stage gall bladder, a single-ended Class A amplification program. Typically include pre-preamplifier and promote two-stage amplification to meet the power requirements boldly push. However, ELl56 excellent performance, only about 20V can be driven at full power output, so the pre-stage and merged into an enlarged promote it. In the Hi- Fi amplifiers, the amplification stages should be minimized, so as to reduce the signal distortion in the amplification process and deformation. Before grading bold ECF80 three poles, five poles compound gall, five pole section as signal amplification, three poles as part of a five-pole amplification load. Bile is equivalent to a three-pole non-linear load resistor, and five poles in the gall bladder has a non-linear effect of offset, so that the output of the distortion reduction (works from ZL94212716.1 patents). In addition, due to the presence of bile in the space charge effect, can reduce the noise. Compared with the general resistive load can obtain higher signal to noise ratio, can improve the quality of the signal output of the preceding stage. Adjustable tripolar bile cathode access resistance Wk Wk can be adjusted to change the three-pole bile resistance, so that the pre-amplifier in the appropriate scope of work, to ensure that there is a big 20V preamp output dynamic range, in order to promote full capacity output power boldly ELl56. Indeed, the pre-output range of up to 100V, bold enough to drive any power. Stage power amplifier has an ultra-linear circuits. High efficiency and output characteristics of the three-pole circuit having gall SUPERLINEAR five poles bile, bile is unique excellent amplifier circuit. Since the three-pole tube output low internal resistance, the speaker has a strong control, make good speaker damping, so that the sound is clear, rich layering. Ultra-linear circuit of the machine is achieved by a resistive divider, screen grid voltage negative feedback by: R5 and R6 determine the ratio of the output obtained from the tap without cattle. This super-linear resistor divider circuit, the benefit is by changing R5, R6 best screen grid dynamic negative feedback voltage, the ultra-linear circuits to achieve optimal performance. Also reduces the output of cattle wound difficulty (see Articles related content principles of the 2004). Since the output of cattle wound low difficulty, so the output of cattle native to achieve a higher performance, plus the load frequency response up to 120kHz or more, and laid a solid foundation for the high standard of the whole amplifier. Self-bias amplifier circuit mode. ELl56 string has a regulator DWl cathode resistor Rn. DWl produce stable cathode voltage of about 20V, so there is a suitable gate ELl56 negative operating point. RD is only 47, but can not be omitted, and it has a stable operating point signal negative feedback, can more effectively reduce the distortion amplifier stage. Typically, the cathode voltage amplifier stage is through the cathode resistor shunt capacitance of ways. This is the traditional approach, but need to be sufficiently large to ensure the capacitance low-frequency limit of the amplifier level. HiFi amplifier low-frequency limit as low as 10Hz or less, and the corresponding shunt capacitance F to reach hundreds of thousands of F. This is actually only using electrolytic capacitors, electrolytic capacitors and poor quality, high and low frequency performance is poor, serious damage to the amplifier signal quality. Zener diode (DWl) is currently widely used regulator device. Low frequency response to DC (0Hz), high-frequency response of hundreds of kHz, excellent performance, much better than electrolytic capacitors. However, DWl no DC stabilizing effect, it is necessary to stabilize the series Rn ELl56 DC operating point. A gate connected amplifier stage are Rb, Cb high-frequency boost circuitry to compensate for the high frequency component of the output of cattle loss. Although these high frequency components beyond the hearing range of the human ear, but reproduction is included in this part of the high-frequency component will create more realistic and natural feeling. Enhance the high-frequency components, allowing the amplifier in response to the overall broad, flat, Hi Fi achieve high performance. This is to consider the issue from a global approach, it is also an effective way to overcome the tube amp output cattle noon insufficient frequency. This method can, tube amps and transistor frequency response sufficient to match the machine, reach more than 80kHz, and the tone is also superior. High-quality power amplifier power supply circuit must be full attention. In fact, in the amplifier circuit has been refined case, every step to enhance the power amplifier circuit will make the sound quality improved significantly. The units power circuit uses FET electronic filtering, electronic voltage regulator circuit, better than conventional filter circuit, in terms of performance as traditional circuit unparalleled. Its power supply amplifier circuit to meet or exceed the preamp requirements, close to the ideal level of power. FET used has a special feature that even harmonic FET generated when the work on the whole sound seems to landscaping, sound seem soft, sweet. Filament voltage AC power supply, in order to obtain better sound quality. To overcome possible hum in the heater circuit is connected with a balance potentiometer Wl, adjust wl eliminate hum. In the circuit diagram, the individual elements are not given specific values, these elements select a different value and variety significant changes to the sound quality, sound, but does not affect the state of the circuit. We look forward to readers hands-on, minds choose to bring up the best sound quality, in order to exchange views and learn. Second, selection and production of components Traditional forms of tube amps based components that time, the production of just scaffolding welding mode. This circuit is a mature technology, appropriate to the prevailing level components. Today, circuit technology had developed to the printed circuit, component level has been a qualitative improvement, small volume, large capacity element is quite popular, widely used in printed circuit paved the way. Compared to scaffolding welding, the printed circuit can be said to be more advanced form of circuit technology, not only high efficiency, sophisticated electronic circuits, and easier to implement. As a result of computer wiring, printed circuit can easily achieve the shortest connection between two points and one point grounding ideal form. To pay attention to the wiring of the Hi-Fi amplifier production, the use of printed circuit more desirable. This machine adopts 2mm double-sided gold-plated printed circuit, not only completed the ideal of the wiring circuit, and gold-plated circuit also ensure the high quality of the connection, the signal navigate in the circuit. Structurally, this unit is different from traditional tube amps. It uses a clamshell form, the power of cattle, cattle output, printed circuits and connectors are installed in the bottom box. The whole center of gravity, more stable, in line with the pursuit of sound fever. Production, weld printed circuit completes all electrical connections. The printing plates installed in the bottom box, and a small amount of cable to connect the power supply of cattle, cattle output. After debugging, all production will be all over, like a traditional tube amp without that over and down in the past to carry out the installation, welding, debugging, very hard. Close the aluminum molding on the cover of a beautiful, beautiful, high-quality tube amp on the show in front of us. Structure of this machine is ideal for lovers of DIY tube amp. Selection of all resistance metal film resistors, to ensure that the machine squelch background. Wherein R5, R6 is 3W, the balance being l/2 W. R3 fever greater 6W using small wire wound resistors, for direct soldered to the printed circuit board. RW due to the volume control signal is input, so the use of high-grade Japanese ALPS potentiometer square, not only the whole SNR is guaranteed, but also the two-channel volume control to maintain a high degree of synchronization, will not change the volume of the sound field occurs positioning drift. ALPS potentiometer synchronization excellent, many potentiometers can not be compared. Semi-adjustable Wk, Ws high-quality organic solid potentiometer. Wl is selected precision trimming potentiometers in order to accurately balance hum, so that the AC noise suppression native residue may be comparable to the transistor machine. BY envelope rectifier uses high-frequency control, helps to reduce power supply noise. Capacitor Selection bigger impact on the sound quality, more elegant. Cl, C2 requires the use of CBB capacitor, C05, CF using ceramic capacitors, C04 imported CBB capacitance. Power supply filter capacitor is imported (ruby) large-capacity electrolytic capacitor.