Brand new, never used. One RUI -1 USB Isolator (the current version). I opened the box for taking pictures only. Retail price is 990 euro, now for 749 euro only. Principle and structure: The PC noise that was impossible to control – until now. 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 we 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. Please check our other items. Free shipping worldwide!