There is an ongoing discussion within the audio engineering community about the sound quality of amplifiers concerning the audibility of signal distortions. Apparently, capacitors are suspected to be the source or at least a contributor to high-frequency distortions that influence on distortions.

This application reports a study of total harmonic distortions (THD) caused by commercial electrolytic capacitors, as produced by Würth Elektronik eiSos, as well as purpose-built items.

In order to find parameters that influence the THD, capacitors with different separation paper and electrolyte compositions have been investigated. Those sample capacitors were assembled at near mass production conditions at a production site and analyzed at the electrical laboratory of Würth Elektronik in Berlin.

At first, the appnote provides an introduction into the field of human hearing and psychoacoustics before approaching the study of harmonic distortions in capacitors. It furthermore introduces results from model calculations to check the plausibility of the measured results.

The results suggest that the harmonic distortions are well below the threshold of audibility. It can be concluded that the capacitors do not add significant distortions to fundamental frequencies as they transfer signals. Modifications of the electrolyte or separation paper have a negligible effect on the THD.

Content:

• Introduction to human hearing
• THD of a Capacitor Model
• Experiment Details
• Measured THD of 470 µF Electrolytic Capacitor
• Comparative Analysis of Capacitors

Download: ANP125