Brand new, never used! One RUI-1 USB Isolator (the current version). We opened the box for taking pictures only. The main cause of sound deterioration with PC based audio is the huge amount of noise generated by the PC. PC noise is constantly flowing into the audio system. Not only through the power supply line of the PC, but also through the signal and power supply line of the USB cable. Even if you isolate the power supply of the PC via a noise-cut transformer or drive the PC by battery (DC power), the noise generated by the PC itself is freely flowing into the audio equipment through the USB cable which greatly deteriorates the sound quality. For the signal line an IC (developed by Analog Devices in USA) is used which is normally employed to prevent any malfunction of medical equipment, and for the power line Acoustic Revive selected the latest IC which is far superior in noise removal than the original IC of Analog Devices. As a result, Acoustic Revive succeeded in removing the PC noise through both of the signal and power lines to nano level. Currently, there is no other way to completely cut PC noise, the sound improvement by totally removing PC noise is staggering. You can experience for yourself the super low-noise and a precise sound images on a transparent sound stage. Retail price is 699 euro, now for 399 euro only. Check our other listings for more interesting items. Free shipping worldwide!