Use the dawn collection version 12AX7B to make the daring front magnifier sound
Shuguang Electronic Pipe Factory has developed a variety of high-performance audio amplifiers for Hi-Fi tubes, which are quite reputable. Recently, in cooperation with Hong Kong Mingda Chuangshi Technology Co., Ltd., "alloy scientific structure technology" specially created high-performance "Create Audio Hi-Fi Tube (Creator) Electronic Tube 12AX7, product level is divided into ordinary version and gold assembly Edition. The section of the dawn factory sold is "Sgeltube 12AX7B Collector NO: 01", see Figure 1 (omitted). Collector's 12AX7B and (creation) gold equipped with the pair of pipes are exactly the same, but the pin is unfamed. This electronic pipe manufactured by this application conductor technology has extremely high performance. And the vacuum degree in the electronic pipe is 10-7, and the more common model is much higher. This prevents the impact of gas molecular collision, making the amplifier's signal-to-noise ratio, and the tube service life is also long.
The 12AX7B of the Collector's Edition is also paired. The two tubes are strictly paired by the manufacturers, which is also excellent in symmetry of two triode units in the same tube. This tube is used in the input stage of the timer magnifier or the amplifier amplifier to make two channels to get very good symmetrical, balance. 12AX7 is a tall U, a low noise voltage amplifier double tripode, using this courage to enlarge the amplified sound system, there will be sound, color, and taste the effect. Today it is recommended to use friends using the aspiration or welder.
This article describes the classic gallbladder magnifier MARANTX-7 produced with the Collector's 12AX7B. M7 is one of the most famous electronic tubes in the history of the audio, the attractive thing is the beauty of its sound, and the voice is more emotionally affluent. When replaying the strings, the music is full of glory and strength, sleepy this DIY is very imitation many. This machine uses six 12AX7, three of which are used as a grouper amplifier (RIAA line). Today, the Shuguang Collector's 12AX7B is only used in the line amp part, replay the CD or DVD dish. With three 12ax7b, the two channels have the greatest effect on the sound effects, and the enlargement of the input stage and the intermediate enlargement of the amplifier use a pair of collector's 12AX7B. The output stage uses a dawn generic version of 12AX7B, the performance is still good .
DiY sometimes feels that the timid amplifier of the soldering is not good enough, the termination force and three-dimensional sense is poor, mainly the matching of components, which is the pairing of the magnifier. No requirements, especially the pairing of the input voltage amplifier is often overlooked, and this level is the most influence on the sound effect. Nowadays, there is a collection of 12AX7B, and pay attention to the selection of the selection of the components, you don't have to worry about the symmetry of the two channels, balance the problem.
The whole machine is shown in Figures 2, V1, V2, and the Class A voltage amplification of the two-stage 12AX7B, and V3 is a cathode output. And the gate electrical resistance of the V3 is between the cathode resistors R10, R11, so the gate is not only a self-bias voltage, as well as the positive bias formed by R11, the reason why this machine is good is therefore. The output of V2 also leads to the cathode of the feedback voltage to V1, the feedback resistor R18 is large, so the negative refueling is small, only a few DB. And the cathode resistance of V1 has no bypass capacitance, so the input voltage amplifies double negative feedback, so that the performance of the circuit is improved, and the distortion is very low. The capacity of the output capacitor C4 is more moderate, so the sound is transmitted, the middle sound is full, the bass is strong, and the power part is closely related to the power supply part.
The B + high pressure of the power supply portion is a biliary stream (rectifier dawn 274b, which is also a high vacuum variety) and the π-shaped filter circuit of the choke. The B + output is a gallstave pressure circuit. The voltage adjustment tube V5 is 6P3P with a larger screen stream (72 mA). The voltage amplifier is 6N9p with high U di-triode, which is more sensitive, and the voltage regulator is better. The regulator tube is provided with a cathode of 6N9P to provide a reference voltage to the cathode of 6N9P. This regulated circuit output is a very stable and smooth DC voltage of continuous adjustment (adjustment W2) of 200 ~ 300V. This is very advantageous for improving the signal-to-noise ratio of the entire discharge system. At the same time, the gallbladder is highly improved on the sound of music, the sound of the music, the medium, the bass, the strength, the strength of the bass, so the output capacitor C4 does not need to have a good bass effect. If the voltage adjustment tube of the voltage regulated circuit is small, such as 6V6, 6p1 or with a double tripode 6N6, although it can work normally, the output voltage will decrease, and a lot of inferior. Another solution is still bilestick, rectifying the 5U4G of Nanjing, this gall is a rich variety of music, and the filter circuit of the gay circle, delete the bile steady voltage, B + output voltage from the positive terminal of C6 Output, see the dashed position in Figure 2, connect A, B. The b + high pressure is 320-330V, and the line can work normally, and the sound will be more bright, the performance of the dynamics and treble will be slightly better. However, the thickness of the sound, the amount of bass is slightly inferior, so the visual taste is selected. Of course, it is more comprehensive with 5U4G to add gallbladder. The level of the unit used in this machine should be used in WiMA MKP-10 varieties. B + filter capacitor uses a Philips blue electrolytic capacitor.
When assembling, the three 12AX7B is preferably a word, and the two channels of the opposite elements are arranged on both sides of the magnifying tube, so that the two channels do not affect each other. The power supply partial component is to be left separately from the amplifier circuit. To increase the stability of the circuit work and improve the signal-to-noise ratio. After the welding is completed, the detailed examination is correct, debugging after power is turned on, first adjust the power supply section, the 5th foot of V7 WY3P should have a voltage of about 105V, and the resistance of R15 can be adjusted. After a few seconds, the WY3P tube issued a bright orange glow in the WY3P tube, indicating that the rectification and regulator circuit works, and then adjusts W2. It can be found that the DC voltage of the B1 output (C9) is between 200 ~ 300V or even 310V. Adjustable continuously, then adjust 290 or 300V. Furthermore the working voltage of the large circuit, the numerical value of the cathode voltage of each tube is shown in Figure 2, and the operation of each tube is normal at this time.
Once the voltage is normal, you can access the playback system to listen. This machine can achieve extraordinary effects, sound flavor, stereoscopic, and intravenous performance, etc. This charm should be attributed to the 12AX7B of the Twilight Collector's Edition 12AX7B and M7 daring queen amplifiers.
Author: Dai Hongzhi
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