Power matching
In order to meet the requirements of high-fidelity listening, the rated power should be determined according to the best listening sound pressure. We all have the feeling that the volume is low, the sound is weak, thin, and the dynamics cannot come out, there is no gloss, the low frequency is significantly lacking, and the fullness is poor. When the volume is appropriate, the sound is natural, clear, round, soft and full, powerful and dynamic. But when the volume is too loud, the sound is not soft, rough, and has a sense of ears. Therefore, the playback sound pressure level has a greater relationship with the sound quality. The sound pressure level in the listening area is preferably 80 ~ 85dB (A-weighted). We can calculate the distance from the listening area to the speaker and the characteristic sensitivity of the speaker The rated power of the speaker and the rated power of the power amplifier.
Power reserve matching
Speaker: In order to make it able to withstand the impact of burst strong pulse in the program signal without damage or distortion. Here is an empirical value for reference: the nominal rated power of the selected speaker should be three times the theoretically calculated power.
Power amplifier: Compared with the transistor power amplifier, the power reserve of the tube power amplifier is different. This is because: the overload curve of the tube amplifier is gentler. For the peak of the overloaded music signal, the tube amplifier does not obviously produce clipping, but only rounds the peak of the peak. This is what we often call flexible shear peaks. After the transistor power is placed at the overload point, the nonlinear distortion increases rapidly, which severely clips the signal. Instead of rounding the peak, it neatly cuts it flat. Some people use a composite impedance composed of resistors, inductors, and capacitors to simulate speakers to test the actual output capability of several high-quality transistor power amplifiers. The results show that there is a nominal 100W power amplifier with a phase shift of the load, and the actual output power is only 5W when the distortion is 1%! Therefore, the selection of the reserve of the transistor power amplifier:
Hi-Fi amplifier: 10 times
Civil high-end power amplifier: 6 ~ 7 times
Civil mid-range power amplifier: 3 ~ 4 times
The tube amplifier can be much smaller than the above ratio.
How much margin should be left for the average sound pressure level and the maximum sound pressure level of the system. It should depend on the content of the broadcast program and the working environment. The minimum redundancy is 10dB. For modern pop music, pop music and other music, you need to leave 20 ~ 25dB redundancy, so that the sound system can work safely and stably.
Impedance matching
It refers to the rated output impedance of the power amplifier, which should be consistent with the rated impedance of the speaker. At this time, the amplifier is in the state of the optimal design load line, so it can give the maximum undistorted power. If the rated impedance of the speaker is greater than the rated output impedance of the amplifier, the actual output power of the amplifier will be less than the rated output power. If the rated impedance of the speaker is less than the rated output impedance of the power amplifier, the audio system can work, but the power amplifier has the risk of overloading. The power amplifier needs to have perfect overcurrent protection measures to solve it. The impedance matching requirements for the tube power amplifier are stricter.
Damping coefficient matching
The damping coefficient KD is defined as: KD = rated output impedance of the amplifier (equal to the rated impedance of the speaker) / internal resistance of the amplifier output.
Because the internal resistance of the power amplifier output has actually become the resistance of the speaker, the KD value determines the amount of resistance the speaker receives. The larger the KD value, the heavier the resistance. Of course, the larger the KD value of the power amplifier is, the better. If the KD value is too large, the speaker resistance will be too heavy, so that the pulse front settling time will increase, reducing the transient response index. Therefore, when choosing the power amplifier, one should not unilaterally pursue a large KD value. As a household high-fidelity power amplifier damping coefficient, there is an empirical value for reference. The minimum requirements are: the transistor power amplifier KD value is greater than or equal to 40, and the tube power amplifier KD value is greater than or equal to 6.
The basic conditions to ensure good steady-state and transient characteristics of the playback, should pay attention to the coordination of the equivalent mechanical quality factor (Qm) of the speaker and the damping coefficient (KD) of the amplifier. Part of it. The equivalent resistance of the speaker's feeder should be small enough to be negligible compared to the rated impedance of the speaker. In fact, the power loss of the speaker feeder should be less than 0.5dB (about 12%) to achieve this coordination.
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Barbecue machine is a barbecue food machinery and equipment, its main function is to do all kinds of barbecue products. Mainly used for barbecue shops, mobile barbecue and so on.
The use of rotary grill grill grilled after a piece of barbecue from the barbecue, accompanied by salad dishes, ingredients into a special made in the bread. Visibility, on-site production, and popular in Europe and the United States. Become one of the mainstream street food fast food.
1 power: the range of 800-1600W, according to the actual situation. 2 grilled food: steak, shrimp, vegetables, ham and so on. 3 functions: 3.1 baking pan with a raised stripes, relying on the protruding stripes to bake the food, there will be drainage structure, slope or drain hole. 3.2 baking time is about 3-5 minutes. 3.3 thermostat is adjustable, according to the different food or personal taste to adjust the different. 3.4 heat pipe: According to the different grades of products, choose different specifications of the heating pipe. Generally fixed in the back of the heating plate, using high temperature stainless steel tube or nickel-chromium alloy tube INCO840, the latter cost higher. 3.5 generally do not need PCB control, FireWire to increase the temperature insurance. 3.6 within the wiring: the general use of hidden lines, hidden in the activities of the hinge of the shaft. 3.7 Other: need to take oil device, a separate configuration or drawer type oil box. 3.8 turn on the power, the red power light, the machine warm, until the green light into the food, wait 3 to 5 minutes.
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