Headphone amplifier made with 6n9c, 6N9C Headphone Amplifier
Keywords: 6N9C, earphone amplified circuit diagram
The headphone amplifier circuit diagram of the output transformer is shown. The entire line is still relatively simple, and the installation and commissioning of push line is very convenient, it is basically able to succeed, let's introduce the author's production process.
Using no transformer output, it is very conducive to amateur production. Nowadays, there are many high-quality electronic tube headphone amplifiers, and there is no output transformer, and the capacitor output can be achieved. In fact, use capacitance AC output, it can be easily achieved, which is also conducive to impedance matching.
Although there are many types of tubes, it can be used to drive headphones, good sound quality and low cost, because for output tubes, there is a lower internal resistance, higher cross-guided and larger screen streams. . This machine uses a small power five-pole named 6N9C (6P9P). It uses 4 this tube to form a WCF circuit, which is used to drive low-resistance headphones, and there is no problem in 30Ω impedance.
The feet of the fifth is delicate and round. After the five todes are connected to the triode, the linearity is better, the internal resistance is decreased, and there is no big change in the cross guide. Although the output power is reduced, it is already enough for the headset. This machine uses four old Nanjing's 6n9c. Everyone knows that Nanjing is the cradle of my country's modern electronics industry. The old Nanjing pipe is a domestic boutique. therefore. 6N9C using old Nanjing can get better sound quality tone than ordinary 6p9p. 6p9p is a wide frequency with a five-pole. It can be very convenient to obtain a wide frequency response.
The final working state is WCF, a push-pull line, very similar to SRPP, but it has no voltage gain, and when the screen resistance is optimized to a rogue of a pipe. Its output impedance is basically twice the rogue. therefore. Compared to the SRPP and the cathode output. WCF can get a lower output impedance, which is not only beneficial to drive low-resistance headphones, but also achieve better low frequency effects for medium and high-resistance headphones. At the same time, compared with the cathode output. WCF is due to push lines. It is easier to control noise.
The WCF output section, the 6P9P work point is about 135V screen pressure, 40mA, cathode resistance 44Ω. At this time, the estimated cross guide should be above 11mA / V, the output impedance has dropped below 45Ω, and then the large ring feedback, the output impedance should be as low as 20Ω, and the 30Ω low-resistance earphone does not have any problems. .
The pre-level magnification is connected to an SRPP line by two 6N3. Direct coupling 6P9PWCF. The reason why the 6N3 is selected because 6p9p is a wide frequency with a five-pole, and 6N3 is a high frequency amplifier, which is more advantageous for medium and high frequency, and is connected to SRPP amplification lines. It is stronger for WCF's control. From head to tail. A very wide frequency response and excellent noise control capability can be obtained. After the actual production, the welding is successful, and the sound field, the frequency response is very wide, and it is not a wider. Because it is a direct coupling, substantially 6p9p work points have already determined the work point of 6N3. The 6N3SRPP static work point is: the screen pressure of around 135V, the cathode resistance is 1kΩ, the shed pressure is about 2.6V, so the screen stream is about 2.6mA, which is enough to drive 6P9P.
The power supply is divided into a split dual power supply. The two previously produced lack of lack of 45W six-lamp power cow provides strong power. The author applies such a power transformer to make multiple dual power headphone amplifiers. The effect is very satisfactory. Moreover, this transformer is currently priced. It is really great value compared to the current transformer of "there is a short-two transformer in the market". Since the six-lamp transformer uses the tube rectification. The output voltage cannot be required, so the 1N4007 diode rose is used first. Press, then use 6Z4 as a secondary rectification and soft movement, then the required voltage can be obtained by filtered by the capacitor choke.
design production
The author uses 2.5mm thick aluminum plate into a component chassis. Using a flashlight can be made very convenient. Power connection plug socket with pressure 250V (communication), there is no improper use during use. The split connection is made of a Telflon plated wire, and the heat shrinking tube or plastic casing is covered outside, which is about 30 cm. Because the filament is powered, the cable requires a double strand.
Welding can start from the power box. The 6Z4 filament is powered, requiring a double strand, and is close to the bottom plate and side panel, high voltage alternating line and 6N3 / 6P9P filament. The adverse effects of the communication can be minimized. The exchange of high pressure is completely wavelength of 1 N4007. Then directly into the 6Z4 screen, and carry out the secondary rectification. And play the effect of soft start. Protect 6 N3 and 6P9P. Filtering is combined with a capacitor choke. Among them, the capacitor uses the Philips Blue Hexagon 47uf / 385V, 2 military Morlo 390uf / 400V, and the large radical capacitance can effectively reduce the power ripple and internal resistance. The choke uses Siemens antique 2H130MA (DC resistance is about 150-160 Ω), don't watch the electricity, but the actual application feels very good. A little grounding is used in the power box. Pay attention to the ground line of the two chassis to connect to the sound. The 6N3 / 6P9P filament uses a large current winding of the center tap. After the tap of the two ends enter the power box, go straight to the power output socket, and enter the enlarged box through the electrical cable. The intermediate tap is introduced into the power box, and a capacitor is formed by a capacitor with two resistors. This is because the maximum potential difference between the 6N3 and 6P9P filaments and the cathode is 100V. It must be suspended to the ground.
The large box is more complicated. Because 6p9p is a big eight foot package, four 6p9p uses a lot of space. It must be designed to install the machine. The large box follows the signal or line chart layout, followed by forward. The signal is entered from the back, and the 6N3 is adjacent to the potentiometer. Then straight to the top 6p9p. The upper 6P9P is coupled to the lower 6p9p by the capacitor crosslink, and then output. The potentiometer uses Japanese Alps dual 100kΩ large blue plastic shell 27. This machine is all hand-placed. Be sure to pay attention to the layout of high voltage lines, filaments and signal lines. Signal channel. Whether it is input or output. Try to use the shield line. Grounding a method of combining a little grounding and a common ground. The screen decoupling capacitor uses antique US CD large eight-footed twin capacitors 35uf × 2 / 350V, it should be noted that the negative end of the screen decoupling capacitor must be directly entered. It cannot be connected to 6N3 or 6P9P cathode, because of this, the annoying communication sound may be introduced, and the grounding point is selected from the vicinity of 6N3. It is to be pointed out that the coupling capacitance between 6P9P uses the variety of 0.1uf / 1000V of domestic military green oil, and the effect is very good. The output capacitor uses the electrolysis of Sibib 680uf / 200V. The sound is still very good, and better low frequency response can be obtained due to a large capacity.
What needs to be pointed out. Since the 6P9P third gate is connected to the outer casing, the unit, 6p9p is also connected to a triode. At this time, the upper 6P9P housing will charge, the voltage is about 125V, because, for the old Nanjing pipe, it is absolutely unable to work Touch the upper 6P9P housing for dawn. Although the outer casing is coated with a paint, it cannot touch it, it is best to insulate the upper 6P9P housing, which is more secure. Because even in the power-on state, since the 6P9P is connected to the output capacitance, the high quality output capacitance is often maintained for a long time, once it touches, although there is no big hindrance, the feeling of hemp is not good. Therefore, it is recommended to insulate the 6P9P housing.
After the production is completed, take a closer check to see if there is a short circuit and open. After confirming, insert the tube and energize test. After power-on, you should use your three senses to confirm that there is no serious problem (such as short circuit, etc.), this is "seeing your eyes (different), use the nasal smell (odor), listening to the Early Eye Is there a different (resistance capacitor change color, capacitor leak, electronic pipe screen is red, etc.), should you use the nose to hear whether there is a odor, use the ear to have a vocal (at this time, not the west earphone, listen to the sound of the machine Not the sound inside the earphones). After confirming, the voltage is measured properly. After confirming that normal, you can add a cheap small headset to listen, and finally plug in your beloved headphones, come and enjoy music.
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