Simple and easy to work, Vacuum Tube Amplifier
Keywords: simple and easy to work
The author is a kind of courage, referring to a variety of aspirator amplifier circuits, in the past two years, using domestic tube and existing devices for the existing devices, although the circuit is simple, the playback effect is very good.
The circuit has a 6n11 voltage amplification and inverting per channel, and 6N11 is known as "domestic boutique", which is a low noise, medium μ standard small nine crust double tripod. One of the three-poles is magnified, and the size of the 6N11 anode load has an influentity of its own gain and passband. When the load resistance is large, the voltage gain has increased, but the frequency band is narrow, but also reverse, the circuit uses " The design of the top afterwards, that is, the voltage amplifier screen is very small (only 5LKΩ,), almost a straight line between 10 Hz to 100 kHz. Another triode is loaded inverted. The advantage of this invert phase circuit is that the distortion is small, the frequency is well, and the working stability is high. DC coupling between voltage amplification and inverted phase level is greatly reduced by low frequency components.
In order to reduce the scattering of the 6N11 filament electron, the filament is electrified to be 5.5 to 6V, and one end is grounded. If the 6N11 static screen is large, the thermal noise may increase, so, in the straight line, the static screen stream is small in the straight line, the static screen flow is 3.5 mA, the voltage is about 3.5 mA. Set to 75V.
Remove the RK, so that the power amplifier is working in a class or a class A, 6P3P power tube is amplified (RK = 200Ω,) circuit measurement data is: screen voltage 310V, screen current 100mA (double tube), curtain The gate voltage is 290V, the gate bias is from 20V, and the output power is about 25 W, the distortion is less than 2%. The push-pull power tube should be strictly paired, otherwise the distortion will be large. When RK = 100Ω, the circuit operates in the amplification, gate biasing-15v, curtain gate voltage 245V, and output power 20W.
By adjusting the value of R1, R2, the static operating point of the 6N11 voltage amplification triode can be adjusted. In the preference of the other circuits, the value of R1 is selected from LKω, and the value of R2 is selected from 200KΩ, 150KΩ, 100KΩ, and repeated audition and trials Finally, the values of RL and R2 are set to 340 Ω and L0KΩ, respectively.
The audio output transformer is referring to the 1994 (Electronics News) I. No. 218 (Homemade Upper Machine High Fuel Transformer Export Transformer) Articles I have made, the primary impedance is about 5.5kΩ, the current is not less than 200mA, secondary impedance 4Ω and 8Ω, design power 35W. In order to reduce the decay of the audio output transformer distribution capacitance to the high frequency signal, the initial secondary coil uses a layered winding method, that is, each of the layers of the two layers, the secondary coil is used, and the multi-shaped mold wiring is wrapped around.
Working in the road measurement voltage: 6N11 1 foot 75V, 3 foot 1.3V, 8 feet 81V, 6 feet 200V. Voltage amplification level power supply 256V, poured phase power supply power supply 300V.
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