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Signal path audio7/1/2023 In the case of Class II ceramic capacitors, the capacitance of a component decreases when an increasing positive DC voltage is applied. The voltage applied to a capacitor influences its performance characteristics. The converse piezoelectric effect causes considerable audio signal distortion at lower frequencies, and it is a main source of voltage coefficient in Class II ceramic capacitors. This nonlinear effect leads to audio distortion. In audio amplifiers, this variation in the electrical value of a component results in a signal-dependent gain change. The converse piezoelectric effect affects the rated electrical value of a capacitor. This deformation increases with an increase in the amplitude of the electric signal. In converse piezoelectric effect, a change in electric field results in mechanical deformation. On the other hand, when a capacitor is in unloaded condition, there is uniform charge distribution and the resultant dipole moment is zero. When a capacitor is loaded, the charge distribution is asymmetrical resulting in polarization. ![]() This effect occurs when ionic charges are displaced within a crystal structure. When capacitors are mechanically loaded, some of their crystals misalign and exhibit electrical charges. This phenomenon is commonly referred to as voltage coefficient and varies depending on the chemistry, construction, and type of a capacitor. Although it is important to consider these parameters when designing capacitors for use in the audio path, the two that have the largest effect on the signal path are voltage coefficient and the converse piezoelectric effect.īoth capacitors and resistors exhibit a change in physical characteristics when there is a change in applied voltage. The characteristics of actual capacitors differ from those of ideal components in terms of ESR, ESL, dielectric absorption, leakage current, piezoelectric properties, temperature coefficient, tolerance, and voltage coefficient. Low-cost components with small footprints are commonly used in portable audio systems. In audio electronic circuits, passive components are used for defining the gain, establishing DC-blocking, rejecting power supply noise, and providing bias. Capacitors for use in high-end audio systems In addition, electrolytic capacitors have parasitic diodes that can cause changes to bias or signal characteristics. Some dielectrics materials are piezoelectric and the noise they add to a capacitor manifests itself as a small battery inside a component. The small batteries due to these parasitic thermocouples can significantly affect the performance of a circuit. The ability of a capacitor to handle ripple and allow high-frequency signals to pass is dependent on the ESR of a component.Ī small voltage is produced at the point where two dissimilar metals are joined due to a phenomenon known as Seebeck effect. Changes in the bias voltage can affect various parameters including the quality factor (Q). In amplifier, pre-amplifiers, and other circuits containing active components, this leakage can cause a significant change in the bias voltage. To start with, resistance effect causes DC leakage. Typical aging, variations in operating conditions, and component-specific characteristics add complexity to these unwanted parasitic components.Įach parasitic component affects the performance of an electronic circuit differently. The parasitic effects of a capacitor in an audio circuit consist of equivalent series resistance (ESR), equivalent series inductance (ESL), series voltage sources due to Seebeck effect, and dielectric absorption (DA). As a result, today’s capacitors for use in audio applications offer better performance and yield higher quality sounds. The ever growing demand for audio equipment with better sound quality has been pushing capacitor manufacturers to produce components with better performance characteristics. In electronic circuits, actual resistors, capacitors, and inductors in fact behave like active components, and consume power.ĭue to these parasitic effects, they can significantly change audio signals, and careful component selection is required to prevent significant degradation. Unlike active components, ideal passive components do not consume power and are not expected to change signals. These components use energy from power supplies to change the characteristics of a signal. ![]() Transistors, integrated circuits, and other active components have a considerable effect on the quality of audio signals.
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