How to choose a capacitor

How to choose a capacitor

Generally, audio circuits include capacitors such as filtering, coupling, bypass, frequency division, etc. How to more effectively choose and use various types of capacitors in the circuit has a greater impact on the improvement of audio quality.

1. Filter capacitor

      After rectification, since the capacitor used for filtering has a large capacity, electrolytic capacitors must be used. When the filter capacitor is used in a power amplifier, its value should be more than 10000μF, when used in a pre-amplifier, the capacity should be about 1000μF.

      When the power filter circuit is directly supplied to the amplifier to work, the larger its capacity, the better the sound quality. But a large-capacity capacitor will cause the impedance to rise from around 10KHz. At this time, several small capacitors should be connected in parallel to form large capacitors. At the same time, several film capacitors should be connected in parallel to suppress the rise of high-frequency impedance.

2. Coupling capacitor

      The capacity of the coupling capacitor is generally between 0.1μF and 1μF. It is better to use capacitors with less loss such as mica, acrylic, and ceramics for better sound quality.

3. Preamplifier, frequency divider, etc.

      Capacitors used on preamplifiers, audio controllers, and frequency dividers have a capacity between 100pF and 0.1μF, while the speaker frequency division LC network generally uses a capacitor with a larger capacity between 1μF and a few 10μF. CBB capacitors are mostly used in frequency converters. Mica and styrene capacitors are suitable for small capacity. The capacitors used in the LC network have a large capacity, and metallized plastic films or non-polar electrolytic capacitors should be used. Among them, if the inorganic electrolytic capacitors are non-etched, the sound quality can be better.

Basic knowledge of capacitance

1. The classification and function of capacitors

      The electric capacity is composed of two metal poles with an insulating material (medium) sandwiched in between. Due to the different insulating materials, the types of capacitors formed are also different:

According to the structure, it can be divided into: fixed capacitor, variable capacitor, and fine-tuning capacitor.

According to the dielectric material, it can be divided into: gas dielectric capacitor, liquid dielectric capacitor, inorganic solid dielectric capacitor, organic solid dielectric capacitor and electrolytic capacitor.

According to polarity, it is divided into: polarized capacitor and non-polarized capacitor. We often see electrolytic capacitors.

      Capacitors have the function of cutting off direct current and passing alternating current in the circuit, so they are often used for inter-stage coupling, filtering, decoupling, bypassing and signal tuning

Second, the unit of capacitance

      The basic unit of resistance is: F (farad), in addition to μF (microfarad), pF (picofarad), and a less used unit, nF (), because the capacitance of the capacitor F is very large, so What we see are generally μF, nF, and pF units, not F units.

The specific conversion between them is as follows:

1F=1000000μF

1μF=1000nF=1000000pF

3. The withstand voltage of the capacitor Unit: V (Volt)

      Each capacitor has its withstand voltage value, which is one of the important parameters of the capacitor. The nominal withstand voltage of ordinary non-polar capacitors are: 63V, 100V, 160V, 250V, 400V, 600V, 1000V, etc. The withstand voltage of polar capacitors is relatively lower than that of non-polar capacitors. The general standard Said withstand voltage values are: 4V, 6.3V, 10V, 16V, 25V, 35V, 50V, 63V, 80V, 100V, 220V, 400V, etc.