6N2 + 6P3P cheap single-ended, 6N2 + 6P3P Power Amplifier
Keywords: 6N2 + 6P3P cheap single-terminal courage
6N2 + 6P3P cheap single-ended
The author made an electronic pipe post-level power amplifier, the bile duct is 6N2 + 6P3P, the audition is good. Write the production process and steps to sharing with enthusiasts (circuit see map).
First, circuit form
The front stage voltage is amplified by a common cathode amplifying circuit + cathode output, and the column is used in a single-ended circuit, and the beam shot four-pole 6P3P is connected to a triode. In theory, the triode approach is obviously better than the standard pickup and superlinear picking. The only lack of insufficient is low, and the output power is small; the bile ducts in the circuit are in the Action State The screen current has changed small and stable, and the circuit is simple and stable and reliable in the front and rear, and the operation is not based on the orientation and the large loop negative feedback.
Second, the production process
1. The seat is the engineering satellite receiver of 20 yuan purchased by 20 yuan in the old goods market. The transformer is equipped with a horizontal installation. The method of opening the transpressor is to use the fine drill bit in the design position in parallel, and then hold the steel saw blades, and the flattening is flattened, then use the fine sandpaper to polish the smooth. glitch. Although this method is "stupid", the hole is very accurate.
2. Circular resistance, capacitance, etc. have not pursued cost of fever, and they are used for many years of accumulation. The carbon film, the metal film resistance is mixed, but the corresponding position in the two channels is consistent with the same type of parameters, and the power is between 1W, and the individual position is used to 3W. The only coupling capacitor in the circuit is 0.82 μF polypropylene film capacitance, and the filter capacitor is a "black diamond" of the clear color. The power transformer is the finished product from Hebei Yongnian mail order.
Following the principle of "concise first", the power supply is the rectification of the crystal bridge. Although the tube rectification "gallbladder" is more flavored, the supply speed of the current is poor, and the big dynamic play is slightly weak. Filtering circuits use several large capacitance to form a CRC filtering network with a large power resistance.
Select the resistors and capacitors needed by the two channels and place them separately, and measure pairs one by one by multimeter, ensuring that the two channels correspond to position parameters.
The whole machine circuit uses a shed welding, and a diameter of 1.5 mm copper wire is provided between the two power hostees as the ground bus, and the front and rear grades are connected to this line. The signal input seat to the potentiometer reached the gate of 6 N2, and the high quality diced shield line and one end are grounded, and the tube filament is powered by AC. The discharge device connection in the circuit should be as short as possible, the AC power cord, the filament line should be treated with a high-quality wire back to the bottom plate, to reduce the interference of the AC magnetic field, and cannot be with the signal channel of the amplified circuit. The connection is parallel, not close to the gate element of the input stage. The center of the filament power supply should be reliably grounded.
Third, debugging steps
The debugging of the electronic pipe power discharge is a complex and meticulous work. After the entire circuit is connected, do not rush to boot power, should be carefully controlled in the circuit diagram inspection circuit, the components and leads, and use the multimeter Measure the right-ground resistance value of each of the critical points in the circuit one by one.
1. Power-on measurement
1) Measuring the on-site resistance value of the AC feed circuit should be infinite, and the resistance value of the primary coil of the power transformer should be displayed when the power switch is placed at the "ON" position.
2) Measure the value of the ground resistance of high pressure rectifier circuits. The value should be close to or equal to the discharge of the radio.
3) Measure the value of the two-channel front-level power supply circuit. The measured value should be close to or equal to the resistance of the discharge resistor.
4) Measure the value of the ground resistance of each symmetry in both sound channels, and the measurement results should be very close or equal. Be
2. After the power-on measurement has no abnormality in unlining measurement, the same speakers are the same as the output transformer nominal impedance, and perform power-on measurement.
1) No intubation measurement is not inserted into the tube, turn on the electric power supply, measuring the rectified DC high pressure, pre-stage power supply decoupling capacitance positive electrode, the electron pipe seat screen is extremely loaded, the measured value should be The design value is basically consistent.
2) Insert measurement is inserted into the tube after the voltage is not in the intubation, and the power switch is turned on, turn on the power switch. At this time, do not leave the power switch, and there is no excessive heat in the strict monitoring machine, fire, take the fire At the smoke, it is normal to see if the tube filaments are normal. If there is abnormal phenomenon, it should be shut down in time to troubleshoot. As normal, the multimeter can be measured using a DC high pressure. If the high pressure decreases after the load, it demonstrates that the power transformer power margin is too small or the internal resistance of the power supply line is too large. Measuring the electrical values of each electron tube anode and a cathode pair, the screen voltage should be within the range of tube parameters. After the cathode voltage is measured, the OMP (I = U / R) can be used to convert the screen current, and convert the screen power consumption of the tube according to the formula P = UI, this value cannot exceed the maximum screen of the tube. Dispersive power! The two channel symmetry points are measured, and the measured value should be the same. At this time, there should be weak circuits in the speaker. If there is a large communication sound, it is filter, the decoupling or the grounding position is not suitable, and the root cause of the fault should be found.
At this point, this machine is subject to audiovision, and the sound quality performance is basically satisfactory.
In order to ensure that the various tubes are in the best state, the sound quality is better, and the operating point of the front and rear tubes is adjusted.
3. Adjust the static work point of the tube.
1) The pre-stage adjustment of the working point of the predetermined tube is taken in the middle of the gate pressure-screen characteristic curve, the gate negative pressure should be half of the maximum gate of the tube, the working current is adjusted to the largest screen of the largest screen current. % -50% is the best. This machine adjusts the gate negative pressure of the input stage to -1.17V, the screen is about 2.1mA, 6N2 is good, and it is satisfactory.
When adjusting, the signal input is shorter, changing the resistance of the load resistance or the cathode resistance, and the size of the gate negative voltage value and the screen current can be changed, and its relationship is: a. Polar resistance constant, cathode resistance ↑ - cathode voltage ↑ - Gate voltage - Screen current ↓, vice versa. B: The cathode resistance is unchanged, the screen resistance - cathode voltage ↑ - Gate voltage - Screen current ↓, vice versa. When adjusting this level, the onpiculous screen current and gate negative pressure will be affected by the screen resistance and the cathode resistance.
2) Adjustment of the working point of the secondary power amplifier at the linear portion of the gate pressure-screen stream characteristic curve, the amplitude of the input signal of the gate should not exceed the pneumatic value range of the power vessel, which will increase the distortion when it exceeds the distortion. The characterization of the A-class power is that the operating current remains unchanged during strong and weak signal input. When the inspection, the current table can be connected in series in the screen path of the power amplifier, when the gate has a large amplitude signal input, if the power discharge screen is lowered, it indicates that the gate negative pressure is too high. If the screen is high Then, the gate negative pressure is too low. The size of the screen is appropriate, the current is large, and it is good, but the thermal noise will increase accordingly. Small current, small noise, and is advantageous to extend the bile duct life, in general. Adjusting the current of the power to the maximum screen current is preferably 60% -70%. The unit secures the 6P3P gate to -26V, the corresponding screen current is about 47 mA, and the static screen is about 17W.
Because the screen load of the power amplification tube is the primary coil of the output transformer, only the value of the cathode resistance can be changed when the value of the cathode resistance can change the size of the screen (change the cord gate resistance value can also adjust the screen stream value), Its relationship is: cathode resistance ↑ - cathode voltage ↑ - Gate voltage ↓ - Screen current, vice versa. Be
When adjusting the bile duct static work points at all levels, it can first remove the cathode resistance, use a resistance (generally 500Ω-2kΩ), a slightly large potentiometer (preferably wirewind) welding in the cathode At the position of the resistor, the potentiometer is placed in an intermediate position, and the potentiometer is rotated in the upper left and right, until the appropriate voltage value is displayed on the voltage meter, remove the potentiometer, and use a metrophotometer. Replace the resistance of the same resistance value. It is also possible to adjust the sound side until the adjustment is the best, the distortion is the lowest, and the gall is the most concentrated.
After the whole machine production debugging is completed, it will access a pair of car speakers homemade small speakers. Listen to Teng Lijun's "sweet", singing sweetly. Put the male voice audio disc "Moonlight Forest", feel the treble level, the middle sound is transparent, the round is full, the bass is thick. Then use the guzheng, the violin and other strings, the clear and bright sound and the broad range of villages are restored.
This machine is ideal for small places such as books; bedrooms. I believe that with the extension of the time, the sound quality will also have further improvement.
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