J+4 Stereo Line Driver Balanced -10dB to +4dB InterfaceThe J+4 is a stereo interface designed to accept unbalanced low output devices such as instruments, computers or mobile devices and boost their signal to a balanced +4dB level for connection to professional audio recording and playback equipment. The J+4 allows you to boost nearly any stereo signal up to a +4dB balanced line level output, which can be sent over long distances without signal loss and connected directly to pro audio equipment such as