AC LINE Harmoniser,

• Works directly on the AC line, actively introducing a precise range of pulsed frequencies
• Increases the depth and realism of the musical performance.
• Lower perceived background noise.
• Deeper, more dimensional and more vibrant picture on AV systems.
• Mechanically tuned carbon-fiber body
• Gold-plated NEMA or Schuko connector

https://www.nordost.com/qrt/qv2-ac-line-harmonizer.php