table of Contents:
The first chapter of the home theater audio debugging full analysis of the speaker wiring debugging
The second chapter of the home theater audio debugging full analysis of the subwoofer settings
Chapter III Use of Sound Analyzer for Full Analysis of Home Theater Audio Commissioning
The fourth chapter of the home theater audio debugging full analysis of the power amplifier configuration
The fifth chapter of the home theater audio debugging full analysis of the impact of the power supply
The sixth chapter of the home theater audio debugging full analysis of the two-line crossover
The seventh chapter of the home theater audio debugging full analysis of the top ten lies in the audio industry
The fifth chapter of the home theater audio debugging full analysis of the impact of the power supply
Mr. Deng inserted the detector directly into the wall plug, and the noise value at this time was shown as 110.
When the detector passes the MS HD POWER power filter, the noise value becomes 0.5, which is almost "silent and silent", and the effect of the filter is obvious.
The basic principle of the power supply filter The power supply filter is composed of a low-pass filter circuit composed of an inductor and a capacitor. It allows a DC or 50 Hz current to pass, and a large attenuation of a high-frequency interference signal. Since the interference signal has two modes, differential mode and common mode, the power supply filter has attenuating effect on both types of interference. The main indicators of the power filter When we choose the power filter, we should mainly consider three aspects of the indicator; the first is voltage / current, followed by insertion loss, and finally the size of the structure. Since the interior of the filter is typically potted, environmental characteristics are not a major issue. However, the temperature characteristics of all potting materials and filter capacitors have an effect on the environmental characteristics of the power supply filter.
a) The influence of voltage and current on the use effect The power supply has AC and DC points. Correspondingly, many manufacturers' power filters are also divided into AC and DC. In principle, the AC mains filter can be used on both AC and DC power supplies; however, DC power filters cannot be used in AC applications, mainly because the capacitors in the DC filter have a low withstand voltage. And it is possible that its AC loss is large, resulting in overheating. Even if there is no problem with the withstand voltage of the DC filter, since a large-capacity common-mode filter capacitor is used in the DC filter, if the AC current is used, the leakage current exceeds the standard. Therefore, the DC power supply filter must not be used in AC applications. The AC filter is used in DC applications, and there is no problem from a safety point of view, but it costs cost and volume. In the prototype phase, if there is an AC filter on hand, it can replace the DC filter. When the operating current of the line filter exceeds the rated current, not only will the filter overheat, but also the low-frequency filtering performance of the filter will be reduced. This is because the inductor in the filter will saturate at a large current and the actual inductance will decrease. Therefore, when determining the rated operating current of the filter, the maximum operating current of the device shall be taken as the standard to ensure that the filter has good performance under the maximum current state. Otherwise, the device will be interfered when the interference occurs under the maximum operating current state. Or the conducted emission exceeded the standard. When determining the rated current of the filter, there must be a certain margin; in particular, people are accustomed to calling the "effective value" of the alternating current, rather than the "peak" of the alternating current, it is necessary to leave a certain margin. The rated current of the general filter should be 1.5 times the actual current value.
b) Effect of insertion loss on the effect of use: Insertion loss is the most important indicator from the perspective of suppressing interference. Insertion loss is divided into differential mode insertion loss and common mode insertion loss. How to select the power supply filter to determine the required insertion loss. First, do not install a filter at the power inlet of the device, measure the conduction and conduction sensitivity of the device, and compare it with the standard to be met. How many decibels differ, the role of the filter is to make up for this gap. Taking the conduction emission of the device as an example, the process of determining the insertion loss of the filter is given. First, the maximum envelope (a) of the conducted emission value of the device is compared with the limit line (b) given by the standard, and the difference is calculated to obtain the required insertion loss value (c). Since the power supply filter is a low-pass filter that converts the insertion loss line (c) into a form of low-pass filter insertion loss (d), (d) is the insertion loss value required by the filter.
Note: (d) is not a characteristic of the low-frequency filter, but a characteristic of a band-stop filter, which takes into account the non-ideality of the actual filter (see next section). However, if a filter with an insertion loss value satisfying (d) is selected from the manufacturer's product sample, it will fail in all likelihood. Because the data on the manufacturer's product sample is measured under the condition that the impedance of the filter is 50Ω, the actual use condition is not the case. Therefore, under actual use conditions, the insertion loss of the filter is reduced. To be on the safe side, a 20 dB margin should be added when selecting a filter from the product sample, which gives (e). The filter is selected from the sample and its insertion loss should meet the requirements of (e). The difference between the actual power supply filter and the ideal filter is that the power supply filter is a low-pass filter, but the actual power supply filter is usually a band-stop filter. The reason for this difference is the non-ideality of capacitors and inductors. The leads of the capacitor are inductive, and there are parasitic capacitances on the inductor. Although these inductors and capacitors are small, their effects are not negligible when the frequency is high. Therefore, the low-pass filter circuit composed of the actual inductor and capacitor becomes a band-stop filter circuit when the frequency is high.
In addition, the coupling between devices at high frequencies is also a cause of the reduction in insertion loss of the filter in the high frequency range. As can be seen from the figure, the distance between the devices has a great influence on the high frequency performance of the filter. This effect is already evident at 1MHz. Therefore, even if the circuit structure of the filter is completely the same, the high frequency performance of the device will be much worse due to the different characteristics of the device, the way the device is mounted, and the internal structure. The circuit structure of the filter only determines the low frequency characteristics of the filter. In order to improve the high-frequency performance of the filter, it is necessary to pay attention to the manufacturing process from many aspects, such as selecting a capacitor with a small inductance, making an inductor with a small parasitic capacitance, making the lead of the capacitor as short as possible, and properly isolating inside. The Importance of High-Frequency Insertion Loss in Power Filters Many people believe that since the upper limit of the frequency of the conducted emission limit is 30 MHz, there is no need to require high-frequency attenuation of the filter. This is a misunderstanding, and it is the concept of this kind of error that has led many people to go a long way in making the equipment meet the electromagnetic compatibility standards, wasting a lot of time and money. Since the cable on the device is a highly efficient radiating antenna, when there is a high-frequency conduction current on the cable, strong radiation is generated, so that the device cannot meet the radiation emission limit value. Therefore, when there is a high-frequency interference current on the power line, radiation is also generated, so that the radiation emission of the device exceeds the standard. For a person without electromagnetic compatibility experience, this problem is difficult to find; because when the device he developed has radiation emission exceeding the standard, it will be checked from the chassis, signal cable, etc. (this is in many textbooks and training courses) Introduced), and simply did not think it would be a problem with the power cord. Especially when the power line conduction emission of the equipment has met the standard requirements, it is unexpected that the power line should be checked again for problems. Therefore, the high frequency characteristics of the power supply filter are very important.
Special note: When the radiation emission of the device is unqualified, don't forget to check the common mode conduction emission of the power line. In many cases, the radiation emission exceeds the standard due to the common mode current on the power line.
Playing with electricity? It’s weird. Yes, audiophiles must play with electricity! And there are quite a few famous halls inside. In fact, the ideal 220V utility power is as important as the line shock absorber, and even more important in some aspects. After most enthusiasts put the equipment into the room, plug the power cords of all the equipment into a common power supply board, and then insert the socket into the wall. Is it wrong? No! Just do this and ignore several affecting equipment. An important part. There is also a less "playing electricity" fun. Next, I will talk about my experience over the years. In fact, the so-called experience is just a practice summarizing the gameplay of the seniors. It is only for the reference of the devout, and it is not appropriate for the "God".
First, pull the cable from the switchboard
It is ideal for conditional enthusiasts to pull a separate line from the low-voltage panel under the user's transformer, but this is almost impossible for most enthusiasts, so we won't discuss it. The way to retreat is to pull the line from the switchboard of the building unit where you live. I believe this is not difficult for most enthusiasts. The selected wire is made of high-quality single-core copper wire of about 6 square millimeters. Of course, if you burn it badly and not far from the switchboard, it is better to use a higher quality fever wire. Convenient and simple is the use of 4 square millimeters of four-core cable. As for whether to choose single-core or multi-core, my opinion is: if you use a low power supply voltage, you should use a single-core copper wire; if the voltage is too high, you should use a multi-core cable. This choice is from the perspective of school sound: Generally speaking, when the voltage is low, the sound of the equipment becomes slow, the low frequency becomes fat, the sound density of the instrument is thin, and when the voltage is high, the speed is changed. Fast, low frequency and tight. When the wires are of the same material, the single-core wire is faster than the multi-core wire, the low-frequency control is better, and the sound density is also larger, but it is a bit too high in the case of a high voltage. So at this time, the multi-core line is more balanced. If you consider the power supply voltage and then combine the sound of the equipment together, it will be more comprehensive and more detailed. When pulling the cable, it is best to pull two independent lines, one for the power amplifier, the first level for use, one for the CD player or other audio source. After entering the listening room, close to the place where the equipment is placed, install three to five outlets directly on the wall, let all equipment directly take power from the wall outlet, and try not to use the power supply board. The choice of socket is also very important. There are few ideal products in domestic products. Although there are several products that are made well, they are not suitable for plug models of most audio equipment. In the Guangzhou market, you can often see some American standard disassemble sockets, buy a few to combine into a shell, and fix it to the wall. A power plug for most equipment. After using the dedicated power line, compared with the indoor power supply line before the transformation, the most obvious is the level of sound, the sense of silence is enhanced, the sound field is more open and deep, and the control of the low frequency is improved. There are also some changes that are suitable for people and suitable for equipment. We regard all the electrical appliances in the entire residential building after the switchboard as an "amplifier" composed of multiple electrical units, and our own audio equipment is a circuit unit in this "amplifier". In the power amplifier circuit, everyone knows that using a point or star grounding method can effectively avoid interference and improve the signal-to-noise ratio. Now the household switchboard is regarded as the total grounding point. Other electrical appliances are a total loop, and we pull it separately. The line is an independent circuit, which is quite grounded to the "circuit unit" of our audio equipment. In other words, the current loop is independent, avoiding mixing with the current loop of other consumers, thus effectively avoiding interference and modulation. The principle of the two-wire crossover current loop of the speaker can also explain the mutual isolation between the current loops. The two-line crossover is still equivalent to one wire in the circuit principle, but in fact, the high frequency and the low frequency each form their own current loop, thereby reducing the interference modulation between each other. Think of our new line as a one-way unit, and treat other electrical appliances in the building as one way.
Unit, the input switchboard is regarded as the output of the power amplifier, is it not the same as the double-line sound split?
Second, pull the ground
Almost all of the enthusiasts directly use the lightning protection ground wire on the building. It is necessary to know that it is wrong to play the sound alone. Conditionally connect this ground wire to the probe of the oscilloscope, you can see the pulse interference on this ground line very intuitively. It even has a much higher AC potential difference than the neutral line. Such a ground wire is absolutely unusable. After a friend moved, the sound system showed obvious communication buzzing, and many parties could not find the reason. Later, when the ground wire was detected, it was found to have a voltage of nearly 80 volts. It turned out that he used the common ground wire in the building. . Everything returns to normal after disconnecting the ground wire. This example can explain why some enthusiasts complain that the sound is not good after grounding. It is likely that they used a common grounding ground in the building. From the point of view that such a common ground line is prone to loop interference, even if there is no floating voltage, it is not good. It is better not to be grounded, otherwise it will only destroy the sound. So the ground wire is not available or not needed? According to the author's experience, as long as the internal resistance of the neutral line in your power system to the real earth is small, the difference between the true earth potential is not much 10V (measurement zero) When the line-to-ground voltage can be used, the tap water can be used instead of the real earth. The measured voltage is of course as low as possible. If the LP equipment is not used, the ground wire can be omitted. Of course, the ideal way is to re-do an independent "quality" ground. Everyone knows how to make the specific line, and there is no need to repeat them. Follow two principles: 1. Ground resistance as small as possible. 2, as thick as possible wire diameter.
Third, "real power phase" correction
The new power supply is done, this time you can plug in the equipment to open the sound? And slow, there is still one step to do: "real power phase" correction. What is the "real power phase"? Is this 220V AC also positive and negative? Yes, 220V sine wave AC is not positive or negative, however, this thing is a lot of sound, it is hard to let you divide Come out with a "positive and negative" polarity. Insert the power plug of the device into the socket, turn it on and use a multimeter to measure the AC voltage of the device housing to the neutral line, and get a reading. Make a note of this reading, then reverse the power plug (the three-prong plug is to swap the neutral wire in the socket), re-measure the voltage of the chassis to the neutral, get a second reading, you will find that there will be one of these two readings Big one is small. A small reading is the correct power phase connection. This connection will prevail.
According to the above method, all the equipments are checked and corrected, and then all the equipments are connected. (Do not check under the condition that the equipment is connected, otherwise it is not accurate). At this point, your "real power phase" is corrected correctly. At this time, your equipment, both the sound field and positioning, as well as the background silence have improved. There is also a significant improvement in low-end equipment. This is a common sense that every audio enthusiast needs to know. Those who casually put the device plugs into the socket and put them on the socket, take a moment to try
Look.
It should be noted that the power polarity (zero line and fire line) of European and American equipment is opposite to that of China. Therefore, when using multi-national equipment to jointly match, it is necessary to pay attention to the correction of "real power phase".
Fourth, the power "props"
So far, we have done our best in the small power environment, but we can only deal with the negative problems of the power grid environment. Grid pollution, voltage fluctuations are the two most influential problems for equipment. As a countermeasure, the "props" commonly used by enthusiasts include voltage regulators, voltage regulators, isolation transformers, purification power supplies, filters, etc. How to properly select and use these devices is also a must for enthusiasts.
1, voltage regulator
Applicable to places where the voltage is relatively stable, but the voltage is low or high. The general device is where the power is easy to operate after entering the home. If you consider using a power amplifier together, the power of the regulator should be larger in order not to affect the dynamic and low frequency quality. Generally it is better than 3KW. As long as the grid voltage is not lower than 200V and higher than 240V, it is not necessary to consider using a voltage regulator.
2, the regulator
If the voltage fluctuations in your area are very unstable, high and low, and often reach or exceed the safe use of electrical appliances, then you should consider the use of voltage regulators. There are many types of voltage regulators on the market, but suitable for audio equipment. It is not used much. After trials on several types of models, it is felt that the regulator with a ring-shaped self-twisting transformer structure has less influence on sound. Its internal structure is similar to the manual voltage regulator. It only uses the automatic detection circuit to control the motor to drive the adjustment slip ring. Instead of manually adjusting the regulator, the disadvantage of the regulator is that the regulation delay is longer, but for the audio equipment. It is also sufficient for appliances that do not require very high voltage fluctuations. For the regulator's power selection is the same as the regulator, it should be better. The EI-type transformer multi-group tap-type "stepping" regulator and "magnetic saturation" regulator, due to the large internal resistance, is not suitable for audio equipment selection
use.
3, the filter
In-line filter between equipment and power supply For RF spike interference, RF interference has a definite effect. The product-specific audio-specific filters are more effective, such as the Furukawa 168 power filter, but the price is also very expensive. Domestic brands also have very good similar products, which can be inexpensive. The market can also find some disassembled power filters on imported electrical equipment, which are used to connect to the sound source. There is also a certain effect on the front stage. This filter should be used as much as possible in one machine, and the high current specification is preferred.
of. Avoid sharing one device. It is also wrong to try to enhance the filtering effect by connecting two or more filters in series. No matter what kind of filter is connected to the power amplifier circuit, it will have certain influence on the transient, speed and dynamics of the power amplifier. So most experienced enthusiasts do not advocate the use of filters on the amplifier. Perhaps for those avatars with strong personality, there is a beating effect, and it is not in the scope of discussion. In short, it is not wise to look at the power filter and the negation of the power filter. It is not wise to use it to avoid the shortcoming and play it rationally.
4, isolation transformer
The isolation transformer is used to isolate the equipment from the city grid, which can further improve the anti-interference ability, and the effect of using it in combination with the filter is better. The common power isolation transformer consists of a primary, secondary, and shielded ground plane between the primary and secondary. In practice, the author uses two transformers of the same parameters, the secondary is connected to the secondary, and then the secondary is passed through the capacitor. Grounding to ground, so the effect of the two mergers is better than using a single transformer. The tranquility of the music background makes the space feel better. Using an isolation transformer is the same as the filter considerations, which also affects system speed and low frequency quality. Not recommended for use on amplifiers.
5, purification power
"Clean power" is a very attractive name, which is isolated and regulated. Previously used to clean the computer's working power, and later some "eyes" master applied it to the audio equipment. For places where the quality of the power grid is not high, the effect of this power supply is still very obvious. See Figure 7. The waveform observation of the object through the oscilloscope is really very clean and beautiful. After accessing the equipment, the sound changes beyond the imagination. The sound is clean and clear, the level is clear, and the subtle performance is very good, but the internal resistance of this power supply is still too large, the low-frequency fat is heard, the speed is slow, and the dynamic is also compressed. . Switching to more power (three kilowatts) still does not improve much. The results of the trial show that it is still better used in the preamp and the sound source, and the amplifier is free. However, for a single-ended power amplifier like the 300B, and the dynamic and speed requirements are not too high, the sound will be clearer, clear and delicate when connected to the clean power supply. This is the choice of forgiveness.
After all, these so-called "props" are things other than equipment. No matter which one is used, it will have a certain impact on the sound of the equipment. To be sure, it has both positive and negative effects. If your power supply is not very bad, you still don't have to. Apply a joke, "One more incense burner and one more ghost." The practice of tuning the sound through these things is not to be discussed. How to define the application limit of these "props"? First, according to the stability of the grid voltage, normal Chinese electrical use voltage range is allowed to have positive and negative 10% error, respectively measuring the day and night voltage, as long as it does not exceed this range There is no need to consider a voltage regulator. If you are a rigorous enthusiast, you are very concerned about the impact of voltage fluctuations on the sound, deliberately require the voltage to stabilize at 220V, then you must use a high-power low internal resistance regulator. Second, according to the degree of pollution of the power grid, in the amateur case, the ear can be used for simple judgment; the input signal line of the preamplifier is unplugged, and the TV, computer, fluorescent lamp, refrigerator, etc. in the room are turned on, and then The volume potentiometer is turned to the maximum, and the ear is close to the speaker to check whether the weak current sound is mixed with irregular interference noise. If there is obvious noise, even if you are away from the speaker, you can hear it, then an excellent filter. The device is very important. If you only hear a uniform calm and weak current, then there is no need to use a filter. This method is very limited because there is a lot of interference noise that is inaudible. It is meaningless to introduce the selection principle of various "props" in general, and the recommendation of others can only be used as a reference. To really understand the merits of these "props", you still have to experiment with them. The audio is feverish and the ear is heard.
To compare the effects of using and not using filters, the entire AB comparison process is:
1. Compare the effects of the projector with and without the filter - after use, the depth of field and details of the projector are significantly better;
2, compare the effect of the subwoofer with and without the filter - after use, the low frequency is more clear, powerful, and clean;
3, compare the effect of using DVD player, AV amplifier and no filter - after use, the background of the sound is more quiet, no rough components, the sound is meticulous and soft, the outline of the sound image is more vivid;
4, compare the effect of CY-9500 and CY-700 - CY-9500 out of the sound is more refined, noble, fresh, after all, is a different grade of products.
It can be said that the MS HD POWER filter is very obvious for the improvement of audio and video effects, which is unanimously recognized by the friends present.
Aluminum Cable Trays In Data Room
Aluminum Cable Trays In Data Room
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One of the main benefits of using aluminum cable trays in a data center is their ability to improve airflow. When cables are left loose and unmanaged, they can obstruct the flow of air within the data center, leading to hot spots and reduced efficiency. Aluminum cable trays keep cables organized and out of the way, allowing for better airflow and cooling. This, in turn, can help to reduce energy consumption and prolong the life of equipment.
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When choosing aluminum cable trays for a data center, it is essential to consider factors such as cable capacity, load capacity, and fire resistance. Cable trays must be able to support the weight of the cables and any additional equipment, such as switches or routers. They must also be able to withstand high temperatures in the event of a fire, without compromising the safety of the data center.
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