Polarised electrolytic capacitors which have the most compact design and are therefore used for very high capacities (e.g. for the voltage supply of amplifiers) cannot transfer any audio signals because audio signals are AC signals. The bipolar electrolytic capacitors of the ECap AC Audio Coupling & Signal Cap PLAIN series are made of smooth and thus low-loss foil. This has a positive effect on the sound characteristics. Music is reproduced in more details and nuances. Bipolar electrolytic capacitors such as the ECap AC series have a second aluminium foil providing AC voltage resistance and thus making them suitable for music signals.