Reprinted my audio system: (1) Electronic quarter -frequency power amplifier DIY production process and technical concept

Foreword: Personally, today, to this day, the technical threshold of the amplifier DIY is not high, and it is not worthy of too much discussion, such as frequency, dynamics, signal noise, distortion, separation, etc. The difference between the production of ordinary manufacturers, or even better, the advantages and disadvantages of the audio system depends to a large extent on the performance of the listening environment, sound source and speaker speakers. What we want to share in this article is that, instead of constantly trying to improve the lack of power amplifier circuits, or rely on stacking fever components to obtain a pleasant sound, it is better to work hard on other details, maybe a more realistic shortcut.


1. Although I am a major in electrical automation, the audio technology is only amateur hobby. It is not surprising that there may be biased or errors in individual views;

2. The article is original, and there are a little personal subjective ingredient, which is as objective as possible.

1. The main technologies and components used by power amplifiers

1. The overall performance of electronic frequency frequency is better than the mainstream power frequency frequency, mainly because the circuit structure has the innate advantage, but it is also destined to be atypical characters in HIFI products. Readrily;

2. The frequency frequency point of this power amplifier: The three -frequency main speaker is 800/5000Hz, the super bass deadline is 150Hz, and the output of eight roads is available. In recent years, the output level produced in recent years has high output level and has a volume control. It is enough to drive the pure back stage of home audio. If it is unnecessary, the front level can be saved to make the sound more pure;


3. The independent power output of the Eighth Road uses a power amplifier integrated LM 3886TF to ensure that the performance of each channel is consistent; small distortion, simple lines, good protection functions, the effective value of each power power Enough dynamics;

4. Abandon the independent volume control of various channels with electronic frequency frequency and frequent channels to avoid the effects of sound, noise and sound dyeing of the potentiometer and buffer circuit, so when matching the tuning with the speaker, the power amplifier output is connected in series to decline and the electrostatic adjustment. Although there are some waste of efficiency, it needs to be compromised;

5. The front -level amplification uses a pottery op amp LT1057, which is low noise, dynamic, and strong resolution. It is suitable for various types of music, performs well

6. Band switch 2 × 24 and the precision resistance group composition voltage dual -paid step -by -step volume potentiometer, zero noise, high balance between left and right channels, accurate sound field positioning, disadvantage is large volume;

7. AC power input terminal, use two -level composite EMI power supply purification filters to make this machine work in a pure environment, thereby improving the quality of the sound;

8. Two SPRAGUE 36DX series 75V82000UF large pond capacitors, combined with the rectifier filter capacitor board to provide sufficient power for the amplifier. The disadvantage is that the 220V power supply requires 5A fuse to meet the impact current of the capacitor at the moment of booting. The protective effect of the primary winding of the transformer; because it is eliminated to the soft start circuit, a sufficient high -quality power switch and rectifier must be required;

9. Adopt two imported Panasonic 4 battery cells series 14.8V/16.8V, 3400mA lithium battery pack, forming a dual 15V power supply, providing battery power supply options for the front circuit. It can be used for more than ten hours at a time. The cleaner sound quality, but in the actual sense of hearing, there is very little difference in the entire service power supply of the machine, which is only because of the beauty of the aesthetic feelings;


10. Ultra -large -area combed aluminum alloy radiator to make the amplifier chip play the best performance and maintain a stable working state for a long time;

11. Each set of power supply of the transformer is set up with the corresponding specifications to avoid hidden dangers caused by overcurrent or micro -short circuits;

12. Using first -order RC passive electronic frequency, unique straight amplitude and phase characteristics, audio signal synthesis is not distorted, and the signal -to -noise ratio is high, which is not realized in any high -level frequency. In the experience, the first -order hearing is more natural than the second -order, the details are richer, and the large volume is incomparable. Moreover, my extremely disliked a bunch of zigzagers and potentiometers in the multi -order frequency. Rat shit. The sound is a complex signal that is synthesized by different frequencies. Therefore, the distortion of the phase is not compensated and corrected.

The RC frequency parts of each channel are placed on their respective amplifier chip boards. It is easy to adjust. Pay attention not to too much frequency points. The main speaker three channels are enough; the disadvantage is that the frequency slope is only 6DB/OCT. The adjacent speakers will have it. Some sound waves overlapping interference is mainly concentrated near the high -level frequency point, and the sound wave radiation range narrows, but it may also render some pleasant sounds. The second is to require a speaker with better performance. In addition to these two issues, the first -order non -source division is advantages.

Some distortion or abnormal resonance is below the auditory values, almost ignored, and amateur DIY can be improved by simple and practical methods: using a three -point speaker, the distance between the middle and treble speakers is as compact as possible to reduce sound wave interference; the second is the speaker Try to go to the audio level (human ear), do not deviate too much, to solve the poor departure response. Third, if the speaker needs to be placed horizontally, the bass unit is placed in the inside, so the outer treble is relatively close to the ear. This is a rough geometric phase correction to improve the deviation of synthetic sound waves and original audio. Everything in the world and the coexistence of pros and cons. This requires compromise and science.

The three -frequency main speaker is converted from HIVI Hiwei DIY3.1 kit. It is more like the sound of Beats headsets, rich in details, clear layers, and publicity. %, See the next article “HIVI Hivi DIY3.1 Bookstore Speaker Converting Process”.

13. Using imitation golden throat chassis, the appearance is atmospheric, the inside is wide, which can reduce the various electromagnetic disturbances due to crowded parts. There is no isolation shielding measure inside the machine. The cost of all electronic components used by the amplifier is high;

14. The level watch uses a golden throat drive circuit, which has a comfortable visual effect.

*Communication: The instrumentation of the chassis is unbearable. Relying on a bunch of light -emitting diode through the dial scales, it is very dazzling, and the light inside the surface is seriously insufficient. By using ultra -thin light -emitting diode, wedge into the topic plate, let the lights illuminate into the instrument, and at the same time weaken the dial light transmission strength. After this transformation, the instrument can be soft to the light effect.

Second, the main technical parameters of the amplifier

The boring parameter indicators are more empty, just like the chef made a dish to tell you how many seasonings you have used, because I only have the taste of the dish, here are several parameters unique to this machine:

1. Input impedance: The “merger” and “pure back -level” mode are 47K.

I am an old -fashioned person. As long as the signal -to -noise ratio meets the standard, I habitually choose to enter the input impedance to 47 k or even higher. I always think that this helps to restore the sound, and there is a higher guarantee;

2. Portal noise (short input terminal, three more in the middle of the night, the ears are close to each speaker pro -test): “Pure background” mode, zero noise! Intersection

When the amplifier is “merged”, the volume potentiometer is adjusted to the maximum, and the medium and treble are only a little irritable. It is not heard from about 20cm. It is already a higher level;

3. Magnification multiple: 5 times the previous level, the power chip of the 8th -route in the rear level is 22 times;

4. Continuous and unpleasant average power: generally greater than 100W × 2.

The power calculation of the electronic frequency division is a superposition of the effective output power of each channel. Different music has different output power due to different musical instrument melody and different spectrum.

*Calculated: Take a certain song of the HOTEL CALIFORNIA as an example as an example. By observing the flat watch, the proportion of treble and medium sound ingredients is about 2/3 of the bass channel. About 2/3.

According to the official information of the LM3886 power amplifier chip, the maximum power is 68W, the rear power supply of this machine is 35V, and the horn impedance is about 5 euros. According to the following formulas:

Bass power+high school sound+super bass = total power per channel: 68+68 × 2/3+68 × 2/3 = 158W

Total the left and right channels. When playing the music in this paragraph, the continuous non -distorted power of the amplifier is: 158 × 2 = 316W

(Conservative estimation is equivalent to a full -frequency power amplifier with a rated power of 200W × 2 = 400W, or even better, because there is no power loss of the speaker frequency division, and there is a better transient response.)

*Experience: Many enthusiast players and even novices of the first brothers disdain the chip. In fact, as long as it is flexible and reasonable, you can play a variety of unique patterns. Pay attention to the details of the periphery of the chip. Practical and cost -effective; if you want to improve the driving capacity, in addition to electronic frequency, you can also BTL or parallel chip, or the two can be combined, and the three can be both.

*Communication: There is no doubt that the speakers are still good. This merit has high power voltage, large pond capacitors, rated 600W ring transformers, and large -area radiator. Therefore The following changes:

1. Double 8 -inch floor -type main speakers. The medium sound unit should use a vertebral speaker with a lower resonance frequency. The frequency frequency point is generally set at about 500Hz/4000Hz. You can adjust it according to the characteristics of the speaker;

2. Cancel the heavy bass, the original heavy bass channel of the amplifier is changed to a second bass, and 500Hz or below is set to the frequency of the frequency. Many speakers in the market are common problems caused by incorrect frequency of boxes;

3. Change the frequency point of the division, you need to adjust the internal frequency frequency parts, the problem is solved by a few dollars, the calculation and replacement are extremely convenient, and the frequency is accurate. You can replace a few ordinary small capacitors. For details, see the first -order first -order. Personalized electrical data;


4. The above suggestions may only be suitable for non -closed speakers.

Third, the regrets and mistakes of the production of this power amplifier

1. The red and white colors of the input terminal are reversed, so when connecting the left and right channels of the sound source;

2. Input terminals are not arranged in order, and the sound source connection corresponds to the number;

3. The acupuncture of the level table is normal to stop at the dial with a little scale. The pointer does not return to zero. You need to adjust the level table drive circuit;

4. The spare switch is used to add the functions of the machine. During the production, the bass and ultra -subwoofer can be switched through this key to convert it into a full -frequency band power output channel. Sexual, give up unnecessary;

5. The electronic frequency RC part gives up the form of independent small board plugging. Instead, it is directly welded to the respective channel power board to improve the signal -to -noise ratio of the machine. It


*Explanation: These little regrets are caused by the negligence and consideration during production. It can be corrected later, but because the machine has been organized after the machine is completed, the noise indicator of the test machine is excellent. When errors, the current situation of better wiring will make the signal -to -noise ratio worse. Therefore, if you give up, if the signal -to -noise ratio is not good, the noise is a superposition of various channels, so you need to pay attention to it.

Tolerance is also a kind of wisdom. Otherwise, it will be self -disturbed. The key is that there is a good sound quality, which is the focus.

*Conclusion: The sound of the sound of electro -sound equipment is never as good as real, not to mention professional musical instruments, even toy piano, octagonal box, etc., crispy and pleasant metal knocking sounds, extended pan sounds, tail sounds, sounds and charm in the world, in the world There is no sound that can be performed perfectly, this is distortion.

The distortion is inevitable in the audio. For the power amplifier, there are only two distortion. One is to flatter and listen to it, such as electronic tube distortion and rendering of certain sounds; Bad and other distortion.

Therefore, playing sounds can pursue better, but don’t be too persistent, let alone go into the magic, except for rich guys.