What is a Line Isolation Box?
These are also known as “line boxes”. With regard to impedance and level, line boxes (in contrast to DI boxes) have an input/out-put transformer ratio of 1:1. Line boxes are used to solve problems relating to ground loops. To provide protection against electric shocks, many devices have metal housings and a power plug fitted with a grounding pin. This ensures that the device housing is grounded. If a fault occurs, the grounding prevents users from coming into contact with dangerous voltages. If you connect up two such devices using a screened audio cable, this may cause a ground loop, which produces a (50/60 Hz) humming noise. The reason for this is as follows: In an ideal situation the ground potential should always be 0 Volts. Cable routes with different lengths and many other complications can cause the ground potential to deviate slightly. By connecting up two devices with different ground potentials the screening allows an equalizing current to flow between the devices. This curre
