Keywords: FU-7 courage circuit, Fu-7 tube circuit
FU-7 asterisk homemade
The 300b single-ended output of the incense, I don't know how much enthusiasts, and even some people make it a fever supreme realm. But less than 10 watts of power limit, it limits it to match some low-efficiency high quality speakers, which can't be said to be a regret. If there is a sound quality of 300B single-ended output, there are 300B push-pull output power, and dynamic, damping, and analytical power exceeds its excellent amphimei, I believe that many enthusiasts have dreamed of. Unfortunately, it is possible to achieve this requirement, the price is no longer an ordinary people to ask. However, for the "artillery" enthusiasts, we will play our own specialties. It is also possible to do a sound quality and excellent courage. The current potential technology has no secret file, debugging points, production crafts very Mature, as long as you are willing to do, you can succeed, the difference is only the sound of the sound, this article introduces a "artillery" on the enthusiasts like a "artillery" in the medium and high frequency, the single-ended power amplifier production of 300B And the density texture of the sound and the analytical force should exceed some.
Principle: Voltage enlargement uses a 6dj8 (6n11) to receive an SRPP circuit This is a circuit that is popular in recent years. Compared with the traditional classic co-amplifier, high-frequency, high frequency response, output The worker of impedance is low and easy to debug. The tone orientation is relatively smooth, and the speed is faster. It can be understood as the characteristics of "sound resistance", but it is worse than the "gallbladder" of the large circuit. This level plays a key role in the tone of the whole machine. When 12AX7 (6n4) is used, the working current is selected from 3.5 mA, and the host can obtain a more "music taste", the second level, the second level, the 6SN7H (6N8P) plus constant stream, the long tap Circuit, about 15 dB gain. The transistors BG1 and D1, R11, R12 constitute the constant current source of the inverting circuit facilitates the balance and decrease of the two arms of the circuit. The inverted level of operating current is very large, and the sound quality of the whole machine is very large. Please select R12 to be selected between 4-8mA, and the author takes 6mA. It is too large or too small, and it has a crucial impact on the treble and bass. It is more warm and medium in the current hearing. It is relatively dim, and the high-band is relatively dim, and the current high frequency should be better, and the intermediate frequency loss is partially thick. The specific selection is fixed by your personal taste. The third level power output stage uses four Fu-7 parallel push output. It is not just for cheap, more importantly, its vocal performance is not much more than the famous 300B. DIY master with Taiwan praised Fu-7 on the music of the music, more "humanized" than 300B. Another point is that this machine uses two tubes to franchise. Generally, after the bile duct is connected, the low frequency of the sound is lowered, the sound density is increased, and the high frequency is changed, and the analytical force has different degrees of decline. After experiment, different bile ducts have different differences, once tried EL34, KT88, and the overall performance of the output power was increased. When the fu-7 is loaded in parallel and single-tube when loaded in 6kΩ, the high frequency difference is extremely slightly micro, the medium frequencies increases, and the sound is more rich; the improvement of dynamics, control, and output power is intended. Each FU-7 operates in 480V, 50mA, power consumption of approximately 2W, close to the maximum anode dissipation power of 25W of Fu-7, but as long as the authentic pipe, there is no problem. The author's prototype has been used in the end of any aging, not to mention the price of KT88, with sufficient market supply, and FU-7 can be one of the most value-for-money bile ducts. FU-7 is connected to a triode approach, and its sound quality is early, although it is a little mighty masculine, but it can be compensated after using a bilayer. Since the opening-loop characteristics of the whole machine are very good, the large-loop negative feedback value of this unit is low, effectively reduces the negative influence of the transient distortion and high frequency phase shifts from the negative feedback of the large loop, so that This excellent transient response. Only one level capacitor coupling in the whole machine is small, the impact on the sound quality is not rooted, and the supplement capacitor can be used. I have experimented several famous capacitors, such as WiMA, ERO, Sulen, etc., the final author used WiMA capacitors, and took the sound of the sound, the analytical force and the speed of the speed. If you like the performance of "music flavor", you can use the Suleng capacitor. Be
Production: The production of the chassis can be referred to FIG. 2. The selection of materials has a certain impact on the sound. It has been experimentally experimenting over the iron plate, aluminum plate, stainless steel plate, etc., different materials have different effects on the tone. The aluminum plate is ideal, but it is not very ideal from sound effects, and its voice is a bit divergent, and the sound is a bit blurred. The iron plate is not enough, the reason is very simple, and the inner magnetic energy of the rack is very unsatisfactory. The disclosure magnetic field of various transformers produces complex electromagnetic interference in the iron plate, and magnetically coupled to the components near the iron plate. Causes sound quality pollution. In the author's experiment, use the same components and circuits, when making a rack with iron plates, the sound quality can be deteriorated. Stainless steel plate is a controversial material, some people accuse it, but the author's comparative experiment does still feel better than aluminum plates and iron plates. It is mainly manifested in the sense of intensiveness in the medium and low frequency bands, and it is impossible for other two materials, and more beautiful. The disadvantage is that the hardness of stainless steel is high, and the processing and production in amateur is more difficult. Output transformers are the key to success or failure of a biliary system, and this machine is bypassing high quality core and an oxygen-free copper wire. The winding method is more complicated. The primary and secondary are separated from each other, and the primary is divided into three groups of six groups. On one side. The secondary is in the same method to wind it in the primary layer. There is a gap between the circles and the circles, which cannot be wound, a good high-frequency response. Note that the tap of each winding should not be mixed. After the core is inserted, the core is inserted, and the secondary is connected to the alternating current, then connect the primary winding tap. Note that the measured voltage per connected should be increased. If the reduction is connected, it should be called until it is The superimposed voltage is highest (the same connection). As long as you carefully, follow the graph, the success rate is extremely high; more than some fake names are much more. The core size is large, the medium is low, but the leakage, the leak, the distributed capacitance is large, and the high frequency frequency is lowered. The iron core is small, the medium and high frequency are good, but the medium and low frequency are different, and the sound is thin. Regarding the material industry of the core, there is also a debate. Now the finished output transformer on the market has basically used a high value oriented chip, a small size and low copper consumption, which can reduce distributed capacitance, inductance, and a good high-frequency response can be obtained. The classic median silicon steel sheet is used, under the same parameters, the sound is warm and the gallbladder is more rich. After countless experiments, take 4 × 6 median silicon steel sheet Cartron Cartron, according to the figure, achieved good frequency, hearing also extremely sound (in the actual production of this machine. Electro-electron with two 275W Electronics) The iron core transformation of the output transformer of the Nalang Machine). The power part is very important. This machine is a double mono design and requires two power cow. The author uses a 450W core routine topack, and will not be described again. The blocking circle is also a controversial component, which is a little, but it is certain that it can be sure. That is unfavorable to the use of the resistance to the use of the power supply and transient reactions. The author believes that as long as the DC corrugation of the power supply is small enough, it is not better. After the rectification, in addition to the first level filtering, the other filter capacitors were all encapsulated with CBB60 polypropylene capacitors and plus # 0.68ufcbb small capacitance. Multiple use of motor boot capacitors 30UF / 500V (Note: The market is reported to the multi-motor start capacitance is packaged after two polar electrolysis passengers. This capacitive quality is very poor, absolutely not use!). If the bottom plate is large enough, the first level filter capacitor is also changed to CBB, but pay attention to the capacity is sufficient. You will find this is a "trick". The author often uses this method when giving the gallcham machine, and tries repeatedly. In the middle and frequent quality, the analytical force is obviously better than "high-speed electrolysis", "audio special electrolysis". Again, it is that the capacity of filtering cakes is large enough. If there is a balance of the pressure, it will seriously affect the sound quality, which is relatively simple because the circuit is relatively simple, and it is more conducive to the sound quality, and welded components. The wire should be cleaned first. After the deoxidation layer is used, the flux can be welded, and the flux-like mixture can be used, and do not use the solder paste. The wiring of the amplifier is very important, and the experience is less abundant. This machine uses independent lines of all levels to aggregate the power supply, and then grounded on the rack near the input socket, the so-called grounding method. The ground wire used must be as thick as possible, preferably a single crude copper wire. The quality of the early domestic electronic Naji (before the 1980s) is reliable, 6N8P, 6N11, Fu-7 are all models of the sound industry, completely can be relieved (see Figure 5) until the product after the 1980s is mixed. It is difficult for the stability and consistency of the product, it is not necessary. In summary, a self-made amplitude of the self-made courage is the elimination of the eradication of the output transformer with the careful production and commissioning close-related, although any component is selected, or a debugging step, it is not necessarily The sound quality has a great influence, but a little bit dropped, there is a lot of accumulation, the impact of the sound quality cannot ignore the different brands, different production periods, and different production processes. And different working conditions, there are different tone personality. In particular, electronic Najo Capacitors, proficiently grasp the soundness and characteristics of these components, which are essential to successfully produce a high-level homemade and aspiration.
Debug: 1) Adjust the four gate negative pressure regulating potentiometers, so that the current of the corresponding four Fu-7 is 50mA, and then adjust it once after 1 hour (new pipe to be aging, that is, no high pressure, let the filament ignite 15 minutes). Then turn on the high pressure, adjust the gate negative pressure, respectively, at 10 mA, 20 mA, respectively, 10 minutes, and then increased to 50 mA. 2) Adjust the constant current source resistor R12 to make the inverted grade current of 5 mA. 3) The current of the SRPP amplification must not be less than 6mA, otherwise the tone is discounted, and the reduction resistor R3 can be increased. 4) 6DJ8 and 6SN7H filaments are not grounded, but by the voltage of 100V + voltage by dividing the two balance resistance, it is not drawn in the circuit diagram, and the reader can design itself. This is because the cathode potentials of these two levels are above 100V, which exceeds the maximum cathode ribbon voltage. 5) The school has a negative feedback phase. Since the local negative feedback is small, the phase reverse is not necessarily a whistling, and the experiment of the negative effects can be done. If the sound sound increases after the disconnection, the feedback phase is correct, if the sound is smaller. Explain the phase reverse. The output cattle can be sent to the two input terminals. When observing that there is no signal, if the FU-7 screen is red, the treble speaker has irregular noise, indicating that high frequency self-excitement, can be self-contained in the top of the FU-7 top screen The five-circle forms a small inductor, which can generally be solved 6) Do not open the output during power-on, levy from the actuatic output transformer. 7) Inverted phase power supply 380V, which can be increased to 430V, and the control is better. Due to the high gain of this unit, it can directly revoke the CD machine to connect the front pole. The performance of the machine has a flavor. It is different from the general medium and low grade, the sound line is clear, and the double monomer structure has an extremely excellent sound field and positioning. Since the open-loop indicator of the whole machine is very good, only shallow negative feedback, so that the sound is full of freshness, jumping and speed. The low frequency is thick and not fat, the bounce is very good, there is no common looseness common loose power, the intermediate frequency of the frequency is particularly satisfactory (Fu-7 is not used in parallel using the function), listening to the vocal voice, especially The famous female singer's voice is full, full of magnetic, and general stone machines have a few more or less have a few more or less, but this machine is not half a point, and the high-frequency interpretation is also Very distinguished, there is a sweet and humid feel, very close to the feeling of 300B single-ended machine. At first glance, it seems to be a little bit, but it doesn't lose analytical force and transpressivity. It is a lot of high enthusiasts. Making such a double monomer machine is about more than a thousand yuan, less than 300B brand machine, the price is very good. In fact, in practice, when a kind of courage is born in your hand, the sense of accomplishment and giving is that any kind of brand-name cannot be given.
Main performance: power: 40W × 2, 8Ω distortion: <0.2 1kHz / 5W frequency: 18 ~ 30000Hz audio-listening equipment: Speaker: 1) AE1 1i2) Gentleman Bao unit homemade discharge box turntable: DENOR 2800Al decoder: Li Special 38S Signal Fresh: NBS Small Snake Ring Ring: AQ Midnight 3 "
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