Check the listing for details. Audiolab DC Block Audio Grade Mains Filter & Direct Current Blocker -Black - NEW. Condition: New. Listed at 119.00 USD. Audiolab DC Block Audio Grade Mains Filter & Direct Current Blocker (Black) BRAND NEW If for any reason you are unhappy with the item, you have 30 days from the date you receive the item to email for return instructions. Product DescriptionThe DC Block has been designed to improve the quality of AC electricity that feeds our audio and AV systems. Mains electricity has a fundamental influence on the audio signal as it passes through a system, from source to amp to speakers. The mains supply in a typical dwelling is subject to interference induced by a range of issues, causing the AC waveform to distort before it reaches each component. This creates noise in the audio signal, which degrades sound quality – a situation that continues to worsen as the electrical devices we use in our homes proliferate.