Aluminum electrolytic capacitor selection question and answer capacitors for smooth filtering of audio power sources are widely used in audio components. Filtering, anti-crosslinking, high frequency compensation, DC feedback ... are everywhere. But if it is subdivided according to functions, manufacturing materials, and manufacturing methods, it will not be clear overnight. So narrow the scope,
This article only talks about electrolytic capacitors, and only aluminum electrolytic capacitors used for power smoothing.
Every audio device needs power-except for the passive front stage, since power is needed, the action of "filtering" is indispensable.
Don't argue with me, of course, the use of battery power supply does not necessarily need power smoothing. But the battery charging circuit also has rectification and filtering, so the filter capacitor will still exist.
The formal name of the filter capacitor we are now using should be: aluminum foil dry electrolytic capacitor. In my observation, except Canada
SonicFronTIers vacuum tube preamps used PP plastic capacitors as filters in high-voltage stabilizing lines. All models use aluminum foil dry electrolytic capacitors; therefore, netizens need to know more about it.
In the face of power supply smoothing capacitors, what do you think of first? ─Capacity? Withstand voltage?
Capacitors must have a capacity label on the outer skin of the package, which refers to the electrostatic capacity; it must also have a voltage resistance label, which refers to the operating voltage or rated voltage.
The working voltage (working voltage) is referred to as WV, which is an absolute safe value; if it is surgevoltage (referred to as SV or Vs), it is the surge voltage or collapse voltage; exceeding this voltage value ensures that the capacitor will be drowned by the wave-be careful the capacitor will burst! According to the international IEC384-4 regulations, Vs = 1.15 × Vr when it is lower than 315V, and Vs = 1.1 × Vr when it is higher than 315V. Vs is the surge voltage and Vr is the rated voltage.
The charge energy of the capacitor is expressed by Q = CV, Q is Coulomb, C is the electrostatic capacity, and V is the voltage; therefore, when the voltage value is unchanged, increasing the electrostatic capacity can increase the charge energy. Please note that the capacity unit of the capacitor should be F (farad), but the value is too low due to too high measurement, so use μF more, 1F = 1 million μF. Foreign countries also use mF to mean μF, in fact
mF is not very appropriate, but there is no μ key on the mechanical typewriter, so use m for micro.
With the two parameters of electrostatic capacity and working withstand voltage, if you are buying capacitors, what would you consider next? Intuition is the price. Well, this parameter is very important, and the lower the value, the better. Some people think of the brand first, and insist that Japanese goods are not killed-there is still an eight-year anti-war complex? American goods can only be ranked second, only those made in Sweden or Germany can be ranked first. Well, this parameter is also very important. But when it comes to brands, you can't ignore the series models; because a manufacturer will produce many different series of products, different series, quality and price will be different. OK, let's sort out first, the parameters related to power smoothing filter capacitors are known: electrostatic capacity, rated operating voltage, surge breakdown voltage, price, brand, model series.
There should not be only two or three kittens, and the appearance size should also be very important, because it has weight and pin shape related to it, snap-in
It is a plug-in PC board type and screw is a lock screw type. As for the weight, the same capacity is the same as the withstand voltage, but the two capacitors of different brands are compared, the weight must be different; and the appearance size is more related to the chassis planning. Some capacitors are not full-circle type, a bit like a polygonal type. Philips and BHC have this series that seems to be very advanced. Now let ’s reorganize, add weight,
Appearance size, pin shape-there are nine parameters.
Skin color? Who made this? It's wonderful. Because white, black, and blue plastic packages are used by manufacturers, it sometimes has certain meanings. For example, the Japanese word black on gold often stands for advanced foraudio sound level capacitors. What else can you think of just by appearance? The date of manufacture, 9627 was shipped on the 27th week of 1996; in recent years, Japanese capacitors seem to gradually intentionally omit the date of manufacture.
However, the skin color and text printing are not directly related to quality, so only the date of manufacture parameter is added. Also, don't forget to apply the operating temperature, because 105 degrees C is more suitable for vacuum tube machines than 85 degrees C. If the machine is to be placed in the South Pole, it is best to choose a negative 55 degrees
C varieties.
Don't miss the capacity error. When multiple parallels are used, the lower the error, the better. Now plus the operating temperature and capacity error, we already have 12 parameters in hand, and we should have more than 30% understanding of capacitors.
Do n’t get me wrong, the working temperature of the capacitor does not refer to the environment or the surface temperature-no matter how many degrees, the packaged plastic skin is the same,
It refers to the working temperature of the aluminum foil, so it is absolutely OK to use the 85 degree C variety for the tube loader, as long as the capacitor is away from the tube, it will be safe.
However, several important parameters that are really related to the quality of capacitors are only in the original manufacturer's specifications, and will not be exposed on the finished package skin at all. These important parameters are the focus of this article.
Dissipation factor-loss angle The dissipation factor dissipaTIonfactor (DF) exists in all capacitors, and sometimes the DF value will be expressed as the loss angle tanδ. Think about the loss angle, the existing loss, of course, the lower the better. The loss angle of plastic capacitors is very low, but aluminum electrolytic capacitors are quite high.
Whether the DF value is high or low, as far as the capacitors of the same brand and series are concerned, the temperature, capacity, voltage, frequency ...
Both are related; when the capacity is the same, the higher the pressure resistance, the lower the DF value. Give an example to illustrate, the same brand of the same series of 10000
For μF capacitors, the DF value of withstand voltage of 80V must be lower than that of withstand voltage of 63V. The filter capacitors used in this journal often find people with higher voltage,
Not unreasonable. In addition, the higher the temperature, the higher the DF value, and the higher the frequency, the higher the DF value.
However, many capacitor manufacturers often do not indicate the value of the dissipation factor DF in the specifications, because the value is very high and it is difficult to see. Sweden
Take RIFA as an example, its blue PHE-420 series are MKP plastic capacitors, and its DF value is at least 0.00005 / highest at 0.0008.
However, the white top-level PEH169 series aluminum electrolytic capacitors are not marked with loss angle specifications. If you really indicate the DF value, it may be
1.0000, the decimal point is after 1.
Leak ... Leakage current! Leakage! Best not. But there is no way, the aluminum electrolytic capacitor must produce leakage current when working.
Leakage current is of course low, and its calculation formula is roughly: I = K × CV. The unit of leakage current I is μA,
K is a constant, for example 0.01 or 0.03, each manufacturer will choose a different constant. But no matter what, the higher the capacitor capacity, the greater the leakage current. If you have the idea that the larger the capacity, the better the smoothing effect, please also consider this "leakage current". It can be seen from the calculation formula that the higher the rated voltage, the larger the leakage current, so reducing the operating voltage can also reduce the leakage current.
But reducing the leakage current of capacitors is not easy. Low leakage current lowleakagecurrent-LL series is expensive. I once ordered a batch of low leakage current LL series capacitors from domestic manufacturers. The price is more expensive than many imported capacitors. For leakage current specifications, aluminum electrolytic capacitors are much worse than tantalum electrolytic capacitors. Tantalum capacitors are also available in dry and wet types, but their capacity and withstand voltage are both low.
In addition to special customization, in the face of general products, if you want to reduce its leakage current, you can try to increase the ratio of Vs to Vr. Vs is the surge voltage, and its value is of course higher than the rated voltage of Vr, but the applied voltage (real working voltage) should also be lower than Vr
90% of Vr; it is completely correct to find high pressure resistant varieties.
Equivalent series resistance ESR
A capacitor will produce various impedances and inductances due to its structure, the more important is the ESR equivalent series resistance and ESL
Equivalent series inductance-this is the basis of capacitive reactance.
Capacitors provide capacitance, what is the resistance? Therefore, ESR and ESL also require low ... low; but lowESR / lowESL are usually advanced series.
The level of ESR is related to the capacity, voltage, frequency and temperature of the capacitor. When the rated voltage is fixed, the larger the capacity, the lower the ESR. Some people are used to connect multiple small capacitors into a large capacitor to reduce the impedance. The theory is that the parallel resistance of the resistor is reduced. However, if the impedance of the solder joint of the capacitor pin is considered to be small and large, it may not necessarily be rewarding.
Conversely, when the capacity is fixed, selecting a variety with a high WV rated voltage can also reduce ESR; therefore, a high withstand voltage does have many benefits. Effect of frequency: ESR is high at low frequencies and low at high frequencies; of course, high temperature will also increase ESR.
The unit of series equivalent resistance ESR is mΩ, and advanced series capacitors are usually lowESR and lowESL. If you compare the two characteristics of low internal resistance and low leakage current, low internal resistance is easy to achieve, so the capacitor marked lowESR is quite common. ESR is related to the loss angle, ESR = tanδ / (ω × Cs), and Cs is the capacitance.
Sometimes there will be Z in the capacitor specifications, which has a different meaning from ESR, but the calculation of Z is related to ESR, and also considers the capacitive and inductive reactances, which is the true internal resistance. Just mentioned that the ESR unit of the capacitor is mΩ, which means a large capacitor, if it is 220
For μF small-capacity capacitors, the ESR unit is not mΩ but Ω. Which capacitor has the lowest ESR? There is only one answer:
Sanyo's OS organic semiconductor capacitors!
Ripple current Irac
The dissipation factor DF-loss angle tanδ, leakage current, ESR-equivalent series resistance, etc. mentioned earlier are as low as possible, but the ripple current ripplecurrent to be mentioned is as high as possible. Especially now that special attention is paid to the post-stage amplifier to have a large current output, the ripple current Irac (or Iac) of the power smoothing filter capacitor is particularly prominent.
The marking of the ripple current Irac should have at least two specifications for low frequency and high frequency operation. The low frequency is about 120Hz and the high frequency is about 10KHz. However, there may be slight differences between different manufacturers.
The ripple current is proportional to the frequency, so the ripple current is also relatively low at low frequencies. But for our audio fans, the low-band Irac value is important. Therefore, when purchasing capacitors, the number of ripple currents is extremely important. Under normal conditions, the ripple current of lock screw type capacitors is usually higher than that of snap-in plug-in PC boards. There used to be a saying: RIFA's 10000μF is equivalent to 15000μF of other brands, because most of the ripple current of Japanese capacitors is not high, and RIFA is particularly high, so it seems that one can be used as two. German Siemens and British BHC capacitors are often superior to Japanese products in this feature of Irac. As far as I know, Irac's largest capacitor is Siemens SIKOREL
The series capacitance is the highest, 6800μF / 63V is as high as 20A! In the case of small-capacity capacitors, the largest for Irac is SanyoOS capacitors.
In terms of the action of the post-amplifier, many people will assume that they eat current at low frequencies. There is a way to try: use the DC voltage of the meter
-The voltage drop of any emitter resistance in the lowest DCV range, it is best to point the meter, play the record, turn up the volume of the front stage, pay attention to the swing of the meter pointer, you will find that the low frequency will eat current, four guitar Bounce will also eat electricity! What music is best for run-in post-amplifiers? The first MARS of Holst's "Planet Suite".
Now you should know more than 60%, maybe you want to ask: Is there a small size, low leakage, low ESR, low tanδ,
Aluminum electrolytic capacitors with low error and low price, but high ripple current and high applicable temperature range? Um ... no!
Regarding the capacity error, aluminum electrolytic capacitors have made considerable progress in recent years. In the past, it was -20% to + 40%, but now it is mostly +/- 20%.
However, its capacity is often biased rather than biased, so 10000μF may be close to 12000μF when measured.
Accurately measuring the electrostatic capacity of large-capacity capacitors is something I have wanted to do for many years. Do not doubt that this kind of test instrument is difficult to buy. It has been manufactured in the United States and can be measured to 99999μF, and can display both DF value and ESR value; and the electric capacity is
The average value of three-phase (not two-phase) frequency test of 100Hz, 1KHz, 10KHz. This kind of instrument has appeared in the domestic market,
TWD NT $ 100,000-only a leakage current test.
The safety of the rated working voltage, in my standard: at least 15%. For example, the rated voltage of a capacitor is 50V,
Although the surge voltage may be as high as 63V, I can only apply a maximum of 42V. Let the rated voltage of the capacitor have more margins, which can reduce the internal resistance, reduce the leakage current, reduce the loss angle, and increase the life. I have seen Japanese-made amplifiers before, and the working voltage of ± 48V is matched with a filter capacitor of 10000μF / 50V; of course, it will not burn out in a short time, but the life may be reduced after a long time, so you have to replace the new product or buy a new machine. . Therefore, Japanese products often have the fate of "time is up and time to go." You cannot accuse it of cutting corners. After all, doing business is always profitable. If you can only sell you once in a lifetime,
How to make money?
The higher the capacity, the lower the hum?
The most annoying thing is that you can't get rid of it. Someone increased the filter capacitor, and the hum disappeared. I don't believe it very much,
Because the hum of the amplifier is often caused by improper ground loops, the capacitors are minimal. But in theory, the higher the capacity, the better the power smoothing effect, so the practice of large capacity is also believed by many designers and DIY fans.
Therefore, many post-amplifiers, especially American products Krell and Mark Levinson, prefer to use large reservoirs-large capacitors;
Dynaudio in Denmark uses a capacity of tens of thousands of μF even for the pre-amplifier. As for AC & DC AC and DC, they also tend to be "large-capacity", but it is still enough.
However, there are also many famous factories that have taken the low-capacity route. For example, Amcorn of the United States has a 250W × 2 professional post-amplifier with a total of 500W on two channels, and only two 8200μF small filter capacitors are used (it seems to be a bit smaller). Swiss Goldmund is considered Hi-End
Brands and products were sent to various magazines for audition. None of the commentators dared to say that it was bad, and its large rear stage was to use small capacitors.
Swiss FMAcousTIcs are even more expensive. A stereo rear stage can be replaced by a Benz car. Its 220W × 2 professional post-level, known as tens of A current output, I can see with my own eyes, the whole machine only uses two 10000μF / 100V filter capacitors.
The two theories of large-capacity filtering and low-capacity filtering are basically opposite, but they exist in the audio circle at the same time. Designing the amplifier with a low-capacity argument, there can be no hum at all, and the low frequency performance is not worse than the "big water pond" machine. What is the point? Irac
Ripple current. If you are still full of brains, then you do n’t know electrolytic capacitors!
Give everyone a suggestion: if low-capacity filter capacitors are used in the post-assembly stage, a high-power power transformer must be used. That is "thin capacitors, fat transformers", this may be the secret of the loud sound of the amplifier. Based on detailed observations over the past few years, if the post-stage amplifier is to be good, it is more effective to use a high-power power transformer than a large-capacity filter capacitor.
A big one? How many small ones?
OK, some people can't worry, the filter capacitor insists on a large μF ─ that is to find a large one, or use a dozen or so small parallel? Some people say that using small particles not only reduces the internal resistance, but also the response speed, and the transparency and resolution are better.
Mark Levinson and Krell's descendants are not small and big, but who thinks it is slow to react, opaque and foggy? Faced with this problem, I myself have been stuck in a long time.
In terms of chassis planning, it seems ideal to use multiple small capacitors in parallel, and the purchase volume is large and the price is cheap, even the pre-level,
The same capacitors can be used in the latter stage and the integrated machine.
The fate of imported machines is somewhat different from that of domestic machines. When a consumer faces several hundreds of thousands of imported machines with multiple small capacitors, he will self-explain: this makes sense; but when facing domestic products, he may have another A vicious statement: cut corners!
As far as the sound quality is concerned, there should be no absolute relationship between large ponds or small ponds, one large or many small ones. Deng Xiaoping said it well:
Despite its black and white cats, it is a good cat that catches mice.
The manufacturer's brand is also related to quality characteristics. The aforementioned people will not use daily products throughout their lives. The United States originally had two major capacitor brands
Mallory and Sprague, now Sprague has become a great deal, because it was acquired by NipponChemi-con in Japan, and the company name is registered UnitedChemi-Con / UCC for short. However, as long as it is still manufactured in the United States and the cover is made in USA, the trademark change should not be related to the manufacturing quality.
But there are already whispers in the outside world: UCC is worse than Sprague, what is the possibility? Once the Japanese trading company takes over, the marketing policy will naturally change drastically. In order to increase shipments, the selling price must be lowered; but the decline in fake prices will also lead to a decline in quality. Asked local agent Ruipu, UCC capacitor sales are lower than Sprague, showing that domestic manufacturers have rejected UCC. If you compare
The specifications and characteristics of UCC and Sprague are indeed a Japanese sample-the body is greatly shrunk, originally 40mm × 80mm
Changed to 40mm × 50mm, the price may be lower, but ESR increases, Irac decreases-why not make a sigh?
Do you have doubts about daily products? No way, not only the United States, but Germany also needs Japanese funds to enter a German-Japanese cooperation,
Siemens and Matsushita jointly produce S + M capacitors. This is a future trend and is almost inevitable. RIFA
It has long been eaten by EVOX. EVOX is a large group with factories everywhere. The SigEnd single-ended preamp of this magazine has a 1μF capacitor, which is the EVOX brand. Although it is imported from the United States, it looks like a set of products.
Compared with semi-permanent components such as resistors, ICs, transistors and plastic capacitors, the life of aluminum electrolytic capacitors is worth paying attention to. The first is the storage life, which is naturally related to the life span. There should be no problem for 10 to 20 years. Capacitors stored for too long should not be used immediately, use
Powersupply first aging (activation); clamp the terminal, slowly adjust the powersupply voltage, from low to high, the highest can be adjusted to the rated voltage of this capacitor.
It is difficult to understand the working life. The so-called long-life LL-longlife capacitor usually indicates that the ripple current Irac is stable.
Earlier I mentioned that the Irac of the capacitor is related to the operating temperature and frequency, such as 10KHz, 15A at 40 degrees C, 85
It is 9A at degree C; 15A / 9A = 1.67. This number is the life factor of the capacitor (I think of it temporarily). The higher the number, the lower the life, and the closer the number is to 1, the longer the life.
If you remember correctly, 1.93 means 100,000 hours and 1.85 means 200,000 hours, so 1.67 is at least 500,000 hours! However, the main function of the capacitor is the charging and discharging characteristics, so it is not appropriate to charge and discharge frequently. There are two ways to effectively extend the life of the capacitor: one is to reduce the number of startups and shutdowns, and the other is to try to reduce the instantaneous charging current at startup-do you understand? This issue has also noticed this issue, so it has been done for many years.
Even so, if you ask: Which kind of capacitor has better sound quality? This is really difficult to answer. Basically, different brands,
Series of capacitors, its sound performance is naturally different.
I personally do not "do not kill Japanese products", as long as they are handled properly, Japanese products are not lost to European and American products. Used ELNA many years ago
Advanced Cerafine audio-grade capacitors, although their ESR is low, but Irac is not high, installed on amp., The low frequency is very thick,
But the fog is heavy and not transparent enough. But after the speed-up capacitor was installed, it suddenly became cheerful.
Therefore, during the actual assembly, remember to add a small speed-up capacitor to the main filter capacitor. This will "at least" improve the high frequency response. What is the value? It is best to have a large one and a small one, large 1μF, small 0.1μF, MKP is the minimum requirement.
Sometimes it is found that the small capacitor is not helpful, which may be that the small capacitor is not selected correctly. RIFA's electrolytic and plastic capacitors, if you want to add speed-up, advise you not to find WIMA, I suggest you try MIT's PPFX-S tin foil or RTX series 0.1
μF. While writing this article, also pay attention to the advertisements of various magazines, Hi-End of Krell in the US and Class'eAudio in Canada
The new models of the latter level actually use Japanese Nichicon capacitors as the main power smoothing filter! But who dare to say that the magazine commentator is bad? !
The preamplifier cannot eat hundreds of mA of current, so the filter capacitor is easier to choose. High wattage, high output current amplifiers are difficult to serve, and the Irac characteristics of the filter capacitor must be taken into account.
For electrolytic capacitors for filtering, there are a few points that netizens should pay attention to: 1. Generally speaking, the Irac of Japanese products is lower than that of European and American products;
2. Low leakage current is more important than low ESR; 3. Large filter capacitors should be connected in parallel with small capacitors; 4. Choose high voltage capacitors as much as possible;
Fifth, the top capacitors are not high in capacity and withstand voltage, so a large power of hundreds of watts is usually rough and not unreasonable.
The author does not recommend which capacitor is the best, because as long as it is used properly, each capacitor can make a good sound. As for the intentional emphasis on capacitance,
Resistors, solder, and fuses that are not used by xxx brands are definitely laymen who do not understand the circuit structure!
Regarding the structure of aluminum electrolytic capacitors, capacitors can be roughly divided into: one, wound type, two, laminated type, and three, electrolytic type. The electrolytic type is divided into aluminum and tantalum, and aluminum is further divided into liquid electrolyte and solid electrolyte. It is wrong to say that the liquid electrolyte is aluminum foil wet type and the solid electrolyte is aluminum foil dry type, because both aluminum foil dry type and aluminum foil wet type are liquid electrolyte capacitors.
Aluminum electrolytic capacitors use an etched high-purity aluminum foil as the anode, the surface of which is anodized to form a thin film as a dielectric, and thin paper or cloth impregnated with electrolyte as the cathode. Because the electrolyte is immersed, it is called aluminum foil dry electrolytic capacitor.
What is aluminum foil wet? Add electrolyte directly into the capacitor-for example, amine borate + ethylene glycol mixed liquid, this kind of capacitor will shake water when it is shaken by hand, such as PEH169 series of RIFA in Sweden.
Even if it is a famous European factory, the aluminum foil used as the anode is not produced by itself, but is uniformly supplied by a company. It seems that there are many Swiss watch factories, but only a few companies will make oil. When a company in Italy could not normally supply anode aluminum foil about 10 years ago, the famous factories around the world such as Mallory / RIFA / Sprague or Rubycon / Philips ... had to delay delivery and delivery time. How to produce and deliver without raw materials? As for the paper soaked in electrolyte, it is by no means available in general stationery stores. The largest supplier is Malaysia.
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