Keywords: 6N5P electronic pipe straight coupling single-ended power
6N5P direct coupling single-ended power
Circuit
6N5P is a double tripod tube, which is often used in electronic stabilization circuits. If it is used for the audio power discharge circuit, its gate negative pressure is generally at 60 to 80 volts to operate in the linear area, such a high gate negative pressure, if a circuit is constituted in a conventional form, there will be some problems. First, when the self-bias circuit is selected, in order to achieve such a high negative gate pressure, the cathode potential is also mentioned high, and the power consumption on the cathode resistance will increase accordingly, the power of the resistor is sometimes available to 10-15 watts. This part of the power is just to establish a negative gate pressure whitening waste. If otherwise get a negative gate pressure, it is generally not consumed. Second, if a fixed bias circuit is used, it is necessary to add a set of bias circuits that produce a negative voltage to make the circuit complicate. Solve these contradictions, only on the improved circuit. After a period of research on traditional circuits, the author designed this direct coupled single-ended power amplification circuit (see Figure 1). Be
This circuit is designed for power tube designed for a high negative gate pressure, which is basically suitable for all high and negative gate pressure power tubes. It is composed of push-level and power amplification level, in which this connection is rare, especially for power tubes with higher negative gate pressure. As can be seen from the circuit, the two amplifiers are separately powered by two sets of power supplies, and then combined with the two circuits together, form a complete direct coupling circuit. This circuit is a fixed bias, and the direct coupling with the power tube is achieved, and the above defects are completely solved.
Circuit principle and debugging
The working principle of this circuit is not a big difference in the traditional circuit, mainly the coupling circuit, due to the use of direct coupling mode, the frequency band is widely extension. The DC load resistance of the driving stage in the circuit is the same resistance with the AC load resistance, which is basically the gate leakage resistance of the power tube. The anode current of the pre-stage 6N2 generates an upper negative voltage on the gate leakage resistance of the power tube, adjusts the size of the voltage, just establishing a suitable negative gate pressure to the power tube, also allowing the front and rear of the circuit It has established a normal working condition, which is the characteristics of this circuit. Be
The commissioning of the circuit is not complicated. Although it is directly coupled, the work point is mutually implicated, but as long as the law is found, it is easy to debug. Simply adjust the pilot level of the pilot level in this circuit, so that the voltage across the power grid drain resistor is the required value.
Precautions
This circuit has a large difference in the circuit and the traditional circuit. When assembling debugging and use, it is also different from the special circuit, mainly the following points need to pay special attention. Be
1. In the process of debugging and use, it is strictly forbidden to unplug the push-up pipe. Because it is direct coupling, the operating point of the power tube is established by the pre-front stage tube and the circuit, unplug the predecessor tube, will enable the power tube into a severe conduction state, which will damage the power tube or rectification tube. Be
2 The potential reference points of this circuit have two, and each group of power supplies should be used as a reference point in their respective "ground", and should pay attention to when assembled circuits or test circuits.
3. When the actual assembly circuit, the 6N5P gate leakage resistance is as close as possible to the interconnection of the power isolation resistor and is as close as possible to the pre-prime solder. The cathode resistance of the power tube "Place 'side should try to weld the power side.
4. The pre-stage pipe should use the high u tube or the five-level tube, and the increase of the low U tube is not achieved, and the two levels must only be placed.
Output transformer production
When I make transformers, it is the use of commercially available ordinary 30-watt power transformer core, making parameters, and the winding structure are shown in Figure 2.
Performance and listening
This circuit is only magnified by two levels, and the output power can reach 7.5 watts at 1.2 volt input. At 0.8 volt input, the output power can reach 4.5 watts. It is very small from the oscilloscope to observe the waveform, basically can't see, at 7.5 watts; the upper half waveform is a little clipping phenomenon, frequently: 30Hz ~ 22kHz.
Listening: Strong analytical strength, clear level, good people, indicating that the medium sound is good, the bass is powerful, the trend is very crisp, the triangular iron and the copper bell sound.
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