Skills of matching audio amplifier with power amplifier

                          Skills of matching audio amplifier with power amplifier

Four elements of power amplifier and speaker matching' T5 e5 \3 y& r8 J+ \

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The matching of power amplifiers and speakers should pay attention to the appropriate temperature, softness and hardness, so as to restore the neutral tone of the whole set of equipment. This is only an artistic consideration. However, the elements considered from the technical aspect are: Y( W

1. Power matching

2. Power reserve matching

3. Impedance matching 8 S# |& e* D, B1 U" l4 h3 d8 \, q

4. Matching of damping coefficient

If we recognize the above four points when patching, the performance of the equipment used can be maximized and fully utilized.

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With a good speaker, it is very important to match it with a suitable power amplifier.

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power match \0

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 this feeling: the volume is low, the sound is weak, thin, dynamic cannot come out, dull, low frequency is significantly lacking, the fullness is poor, and the sound seems to be shrunk inside and cannot come out. When the volume is appropriate, the sound is natural, clear, round, soft and full, powerful and dynamic. But when the volume is too high, the sound is hard and not soft, rough, and has a feeling of piercing the ears. Therefore, the playback sound pressure level has a great relationship with the sound quality. It is stipulated that the sound pressure level in the listening area is preferably 80~85dB (A-weighted). We can calculate it from 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. 0 X4 | $ L! @4 K

Power reserves match 6 f3 A, N, X, b! r @( T7 X

Speaker: In order to make it able to withstand the impact of the sudden 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. & N; c' m" ?3 j' E2 M* C

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Power amplifier: Compared with the tube power amplifier and the transistor power amplifier, the required power reserve is different. This is because: the overload curve of the tube power amplifier is relatively flat. For the peak of the music signal over the Netherlands, the tube power amplifier does not obviously produce clipping phenomenon, but only rounds the tip of the peak. This is what we often call the flexible shear peak. However, after the transistor power amplifier is placed at the overload point, the nonlinear distortion increases rapidly, causing severe clipping of the signal. It does not make the peak round but cuts it neatly. Some people use a composite impedance composed of resistors, inductors, and capacitors to simulate speakers, and test the actual output capabilities of several high-quality transistor power amplifiers. The results show that when the load has a phase shift, there is a power amplifier with a nominal 100W, and the actual output power is only 5W when the distortion is 1%! Therefore, the selection of the reserve capacity of the transistor power amplifier:! f2

High-fidelity power amplifier: 10 times 8 a3 J" N8 k4 t/ E$ a. j0 u

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Civil high-grade power amplifier: 6~7 times " i# d4 k0 ?& a& |$ q/ W

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Civilian mid-range power amplifier: 3 to 4 times

However, the tube power 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 should depend on the content of the broadcast program and the working environment. The minimum redundancy is 10dB. For modern pop music, disco and other music, 20~25dB redundancy is required, so that the sound system can work safely and stably.

Impedance matching 4 U1

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 power amplifier is in the best design load line state, so the maximum undistorted power can be given. If the rated impedance of the speaker is greater than the rated output impedance of the power amplifier, the actual output power of the power 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 is in danger of overloading, and the power amplifier is required to have perfect over-current protection measures to solve it. For the tube power amplifier, the impedance matching requirements are more stringent. , K6 k9 N

Matching of damping coefficient

The damping coefficient KD is defined as: KD = power amplifier rated output impedance (equal to speaker rated impedance) / power amplifier output internal resistance. Since the output internal resistance of the power amplifier has actually become the electrical damping device of the speaker, the KD value determines the amount of electrical damping that the speaker receives. The larger the KD value, the heavier the resistance damping. Of course, the KD value of the power amplifier is not as large as possible. If the KD value is too high, the speaker resistance damping will be too heavy, so that the establishment time of the pulse front will be increased, and the transient response index will be reduced. Therefore, a large KD value should not be one-sidedly pursued when selecting a power amplifier. As a household high-fidelity power amplifier damping coefficient, there is an empirical value for reference, the minimum requirement: the KD value of the transistor power amplifier is greater than or equal to 40, and the KD value of the tube power amplifier is greater than or equal to 6.

We all know that only by keeping the sound in a stable working state can it bring us better results. In fact, the most important thing is to solve two problems, they are steady-state and transient characteristics. Only by paying attention to the quality of the sound can we make our life more quality. How to do this well, you only need to connect the feeder of the sound If the equivalent resistance is small enough, then it will be fine. Is it very simple?