Capacitors (CAPs) are important components in audio systems. They have different voltage, current and form factors. In order to choose which capacitors are best for sound, moderators need to understand all the CAP parameters. The integrity of the audio signal largely depends on the choice of capacitors. Therefore, when choosing the right device, all important factors must be considered.
The audio CAP parameters are specially optimized for high performance applications and offer more efficient audio channels than standard components. The types of capacitors that are commonly used in audio channels are aluminum electrolytic and film CAPs, and which capacitors are best for sound in particular conditions depends on the circuits and devices used: loudspeakers, CD and musical instrument players, bass guitars andothers.
History of the sound capacitor
The capacitor is one of the oldest electronic components. Electrical conductors were discovered in 1729. In 1745, the German inventor Ewald Georg von Kleist discovered the Leiden vessel, which became the first CAP. Physicist Pieter van Müssenbrook, a physicist at the University of Leiden, discovered the Leiden jar on his own in 1746.
At present, the Leiden jar is a glass vessel covered with metal foil inside and out. The CAP serves as a means of storing electricity, and which capacitors are best for sound will depend on the capacitance, because the larger this figure, the more electricity it will store. The capacitance depends on the size of the opposite plates, the distance between the plates and the nature of the insulator between them.
Capacitors used in audio amplifiers come in several types, such as the common CAP with metal foil for both plates and impregnated paper between them. Metallized paper (MP) capacitors, also called oil-paper CAPs and metalized paper single-layer capacitors (MBGOs) for audio, which are used in AC, DC and pulse circuits.
Later, mylar (polyester) and other synthetic insulators became more common. In the 1960s, metal CAP with mylar became very popular. Two strengths of these devices are their smaller size and the fact that they are self-healing. Today, these are the best capacitors for sound, they are used in almost every electronic device. Due to the huge volume of trade and production of these types of capacitors, they are quite cheap.
Another type of CAP is electrolytic with a special design with predominantly high and very high values ranging from 1 uF to several tens of thousands of uF. They are mainly used for decoupling or filtering in the power supply. The most common in amplifier design are metallized Mylar or polyester capacitors (MKT). Higher quality amplifiers mostly use metalized polypropylene (MPP).
Component technology
CAP technology largely determines the characteristics of devices, and which capacitors are best for sound depends on the class of equipment. High-end products have tight tolerances and are more expensive than general purpose capacitors. In addition, such high quality CAPs can be reusable. High quality audio systems require high quality CAPs to deliver top class sound quality.
The performance, or how the capacitors affect the sound, depends a lot on how they are soldered to the PCB. Soldering stresses passive components, which can cause piezoelectric stresses and cracking of surface-mounted CAPs. When soldering capacitors, you must use the correct soldering order and follow the recommendationsprofile.
All Dacron audio capacitors are non-polarized, meaning they don't need to be labeled positive or negative. Their connection in the chain does not matter. They are preferred in high quality audio circuits due to their low loss and reduced distortion when product size permits.
MKC metallized polycarbonate type is hardly used any more. It is known that the ERO MKC types are still widely used because they have a balanced musical sound with very little coloration. The MKP types have a brighter sound as well as a wider sound range.
A little-known type of MKV capacitor is a metallized polypropylene CAP in oil. It is the best capacitor for audio because it has more powerful characteristics than oil-coated metallized paper.
Quality of passive elements
Capacitors, especially when they are on the output signal line, greatly affect the sound quality of an audio system.
There are several factors that determine the quality of CAP, no doubt very important for audio:
- Tolerance and actual capacity required for use in filters.
- Capacitance versus frequency, so 1 microfarad at 1,000 Hz does not mean 1 microfarad at 20 kHz.
- Internal resistance (ESR).
- Leakage current.
- Aging is a factor that will evolve over time for any product.
The best choice of capacitor applications depends on the application in the circuit and the required capacitance:
- Range from 1 pF to 1 nF - control and feedback circuits. This range is mainly used to eliminate high frequency noise on the audio channel or for feedback purposes such as the Quad 606 amplifier bridge. The SGM capacitor in audio is the best choice in this range. It has very good tolerance (up to 1%) and very low distortion and noise, but quite expensive. ISS or MCP is a good alternative. Ceramic CAPs should be avoided on the signal line as they can cause additional non-linear distortion up to 1%.
- From 1 nF to 1 uF - coupling, decoupling and vibration suppression. They are most commonly used in audio systems and also between stages where there is a difference in DC level, vibration elimination and in feedback circuits. Typically, film capacitors will be used in this range up to 4.7 microfarads. The best capacitor choice for sound and audio is polystyrene (MKS), polypropylene (MKP). Polyethylene (MKT) is a lower cost alternative.
- 1 Ф and above - power supplies, output capacitors, filters, insulation. The advantage is very high capacitance (up to 1 farad). But there are a few downsides. Electrolytic CAPs are subject to aging and drying. After 10 years or more, the oil dries out and important factors such as ESR change. They are polarized and must be replaced every 10 years or they will negatively affect the sound. When designing the connecting circuit of electrolytes onsignal line problems can often be avoided by recalculating the time constant (RxC) for low capacitance below 1 microfarad. This will help determine which electrolytic capacitors are best for sound. If this is not possible, it is important that the electrolyte is less than 1V DC and a high quality CAP (BHC Aerovox, Nichicon, Epcos, Panasonic) is used.
By choosing the best solution for each program, the developer can achieve the best sound quality. Investing in high quality CAPs has a positive effect on sound quality more than any other component.
Testing CAP elements for applications
There is a common understanding that different CAPs can change the sound quality of audio applications under different conditions. Which capacitors to install, in what circuits and under what conditions - remain the most discussed topics among specialists. That is why it is better not to reinvent the wheel in this complex topic, but to use the results of proven tests. Some audio circuits tend to be very large, and contamination in audio environments such as grounds and chassis can be a big quality issue. It is recommended to add non-linearity and natural distortion to the test by testing bridge residuals from scratch.
| Dielectric | Polystyrene | Polystyrene | Polypropylene | Polyester | Silver-mica | Ceramic | Polycarb |
| Temperature | 72 | 72 | 72 | 72 | 72 | 73 | 72 |
| Voltage level | 160 | 63 | 50 | 600 | 500 | 50 | 50 |
| Tolerance % | 2.5 | 1 | 2 | 10 | 1 | 10 | 10 |
| Error % | 2, 18% | 0, 28% | 0, 73% | -7, 06% | 0, 01% | -0, 09% | -1, 72% |
| Scattering | 0.000053 | 0.000028 | 0.000122 | 0.004739 | 0.000168 | 0.000108 | 0.000705 |
| Absorption | 0, 02% | 0, 02% | 0, 04% | 0, 23% | 0, 82% | 0, 34% | n / |
| DCR, 100 V | 3.00E + 13 | 2.00E + 15 | 3.50E + 14 | 9.50E +10 | 2.00E + 12 | 3.00E + 12 | n / |
| Phase, 2 MHz | -84 | -84 | -86 | -84 | -86 | -84 | n / |
| R, 2 MHz | 6 | 7, 8 | 9, 2 | 8, 5 | 7, 6 | 7, 6 | n / |
| Native resolution, MHz | 7 | 7, 7 | 9, 7 | 7, 5 | 8, 4 | 9, 2 | n / |
| Bridge | low | low | very low | high | low | low | high |
Characteristics of models
In the ideal case, the designer would expect the capacitor to be exactly its design value, while most other parameters would be zero or infinite. The main capacitance measurements are not as visible here as the parts are usually within tolerances. All film CAPs have a significant temperature coefficient. Therefore, to determine which film capacitors are best for sound, testing with laboratory instruments is carried out.
The diffusion coefficient is useful in evaluating the efficiency of an electrolytic power supply. This effect on the sonic performance of signaling CAPs is not consistent and may be quite small. The number represents internal losses and can be converted to effective series resistance (ESR) if desired.
ESR is not a constant value, but tends to be so low in high quality capacitors that it doesn't have much effect on circuit performance. If high-Q resonant circuits were built, then it would be a completely different story. However, a low dissipation factor is a hallmark of good dielectrics, which can serve as a good clue in further research.
Dielectric absorption may be more worrisome. This was a major problem with early analog computers. High dielectric absorption can be avoided, so mica audio capacitors can provide RIAA networks with very good audio.
DC leakage measurements should not affect anything, as the resistance of any signal capacitor should be very high. With higher dielectric materials, less surface area is required and leakage is virtually negligible.
For materials with a lower dielectric constant such as Teflon, despite its basic high resistivity, it may be necessary tolarge surface area. Then the leak can be caused by the slightest contamination or impurities. DC leakage is probably a good quality control, but it has nothing to do with sound quality.
Unwanted parasitic components
Transistors, integrated circuits and other active components have a significant impact on the quality of audio signals. They use power from current sources to change signal characteristics. Unlike active components, ideal passive components do not consume power and should not change signals.
In electronic circuits, resistors, capacitors and inductors actually behave like active components and consume power. Because of these spurious effects, they can significantly alter audio signals, and careful component selection is required to improve quality. The ever-increasing demand for audio equipment with better sound quality is forcing CAP manufacturers to produce devices with better performance. As a result, modern capacitors for use in audio applications have better performance and higher sound quality.
Spurious CAP effects in an acoustic circuit consist of equivalent series resistance (ESR), equivalent series inductance (ESL), series voltage sources due to the Seebeck effect, and dielectric absorption (DA).
Typical aging, changes in operating conditions and specific characteristics make these unwanted parasitic components more difficult. Every parasiticcomponent affects the performance of the electronic circuit in different ways. To begin with, the resistance effect causes DC leakage. In amplifiers and other circuits containing active components, this leakage can lead to a significant change in the bias voltage, which can affect various parameters, including the quality factor (Q).
The ability of a capacitor to handle ripple and pass high frequency signals depends on the ESR component. A small voltage is created at the point where two dissimilar metals are bonded due to a phenomenon known as the Seebeck effect. Small batteries due to these parasitic thermocouples can significantly affect the performance of the circuit. Some dielectric materials are piezoelectric and the noise they add to the capacitor is due to the small battery inside the component. In addition, electrolytic CAPs have parasitic diodes that can cause changes in signal bias or characteristics.
Parameters affecting the signal path
In electronic circuits, passive components are used to determine gain, establish DC blocking, suppress power supply noise, and provide bias. Inexpensive components with small dimensions are commonly used in portable audio systems.
The performance of real polypropylene audio capacitors is different from that of ideal components in terms of ESR, ESL, dielectric absorption,leakage current, piezoelectric properties, temperature coefficient, tolerance and voltage coefficient. While it is important to consider these parameters when designing a CAP for use in the audio signal path, the two that have the greatest impact on the signal path are referred to as voltage factor and inverse piezoelectric effect.
Both capacitors and resistors exhibit a change in physical characteristics as the applied voltage changes. This phenomenon is commonly referred to as the stress factor, and it varies depending on the chemistry, design, and type of CAP.
The reverse piezo effect affects the electrical rating of capacitors for a sound amplifier. In audio amplifiers, this change in the electrical value of a component results in a change in gain depending on the signal. This non-linear effect results in sound distortion. The reverse piezoelectric effect causes significant audio distortion at lower frequencies and is the main source of voltage factor in Class II ceramic CAPs.
The voltage applied to the CAP affects its performance. In the case of Class II ceramic CAPs, the capacitance of the component decreases as an increasing positive DC voltage is applied. If a high AC voltage is applied to it, the capacitance of the component decreases in the same way. However, when a low AC voltage is applied, the capacitance of the component tends to increase. These changes in capacity can significantly affect the qualityaudio signals.
THD total harmonic distortion
The THD of audio capacitors depends on the dielectric material of the component. Some of them can give impressive THD performance, while others can seriously degrade it. Polyester capacitors and aluminum electrolytic capacitors are among the CAPs that give the lowest THD. In the case of class II dielectric materials, the X7R offers the best THD performance.
CAPs for use in audio equipment are generally classified according to the application for which they are used. Three applications: signal path, functional tasks and voltage support applications. Ensuring that the optimal audio MKT capacitor is used in these three areas helps improve the output tone and reduce audio distortion. Polypropylene has a low scattering factor and is suitable for all three areas. While all CAPs used in an audio system affect sound quality, the components in the signal path have the greatest impact.
Using high quality audio grade capacitors can greatly reduce the degradation of sound quality. Because of their excellent linearity, film capacitors are commonly used in the audio path. These non-polar audio capacitors are ideal for premium audio applications. Dielectrics commonly used in film capacitor designs with sound quality forsignal path uses include polyester, polypropylene, polystyrene, and polyphenylene sulfide.
CAP for use in preamplifiers, digital-to-analog converters, analog-to-digital converters, and similar applications are collectively classified as functional reference capacitors. Although these non-polarized audio capacitors are not in the signal path, they can also degrade the audio signal significantly.
Capacitors, which are used to maintain voltage in audio equipment, have minimal effect on the audio signal. Regardless, care is required when selecting CAPs that maintain voltage for high-end equipment. Using components optimized for audio applications helps improve the performance of the audio circuit.
Polystyrene plate dielectric block
Polystyrene capacitors are made by winding a lamellar-dielectric block, similar to an electrolytic one, or by laying in successive layers, such as a book (folded film-foil). They are mainly used as dielectrics in various plastics such as polypropylene (MKP), polyester/mylar (MKT), polystyrene, polycarbonate (MKC) or Teflon. High purity aluminum is used for the plates.
Depending on the type of dielectric used, capacitors are produced in different sizes and capacities with operating voltage. High dielectricThe strength of polyester makes it possible to make the best electrolytic capacitors for sound in small sizes and at relatively low cost for everyday use where special qualities are not required. Capacitances available from 1,000 pF to 4.7 microfarads at operating voltages up to 1,000 V.
The dielectric loss factor of polyester is relatively high. For audio, polypropylene or polystyrene can greatly reduce dielectric loss, but it should be noted here that they are much more expensive. Polystyrene are used in filters/crossovers. One disadvantage of polystyrene capacitors is the low melting point of the dielectric. This is why polypropylene audio capacitors usually differ from each other, as the dielectric is protected by separating the solder leads from the capacitor body.
High Energy Density FIM Technology
High power film CAPs offer three categories of this type: TRAFIM (standard and special), FILFIM and PPX. FIM technology is based on the concept of controlled self-healing properties of segmented aluminum metallization films.
The capacity is divided into several million elementary elements, combined and protected by fuses. Weak dielectric elements are insulated, and before punching the fuses, the damaged elements are isolated, with which the capacitor continues to work normally without a short circuit or explosion, as may be the case with electrolyticcapacitors for sound.
Under favorable conditions, life expectancy for this type of CAP should not be expected to exceed 200,000 hours and MTBF 10,000,000 hours. Working like a battery, these capacitors consume a small amount of capacity due to the gradual degradation of individual cells over the life of the component.
The TRAFIM and FILFIM series offer continuous filtering for high voltages/powers (up to 1kV). Capacity varies:
- 610uF to 15625uF for standard TRAFIM;
- 145uF to 15460uF for special TRAFIM;
- 8.2uF to 475uF for FILFIM.
DC voltage range is:
- 1.4KV to 4.2KV for standard TRAFIM;
- 1.3kV to 5.3kV for personalized TRAFIM;
- and from 5.9 kV to 31.7 kV for FILFIM.
The PPX series capacitors offer a complete range of network solutions for GTO suppression as well as blocking CAPs, offering capacitances from 0.19uF to 6.4uF. The voltage range for PPX ranges from 1600V to 7500V with very low self-inductance.
film capacitors for audio generally have excellent high-frequency performance, but this is often compromised by their large size and long wire length. It can be seen that Panasonic's small radial capacitor has a much higher self-resonance (9.7 MHz) than Audience's (4.5 MHz). This is not because of the installed Teflon cap, but because it is several inches long.and cannot be attached to the body. If a designer needs high-frequency performance to maintain stability in high-bandwidth semiconductors, reduce wire size and length to the absolute minimum.
The performance of audio circuits is highly dependent on passive components such as capacitors and resistors. Actual CAPs contain unwanted spurious components that can significantly distort the characteristics of audio signals. The capacitors used in the signal path largely determine the quality of the audio signal. As a result, careful CAP selection is required to minimize signal degradation.
Audio grade capacitors are optimized to meet the needs of today's high quality audio systems. Plastic film capacitors for sound are used in high quality audio systems and have a wide range of applications.
