ABSTRACT
Balanced connections in an audio system are designed to reject both external noise, from power wiring and also internal crosstalk from adjacent signal cables. Balanced inputs and outputs have been used for many years in professional audio, but profound misconceptions about their operation and effectiveness still survive. Electronic balancing has many advantages. These include low cost, low size and weight, superior frequency and transient response, and no problems with low-frequency linearity. A common source of ground-loop current is the connection of a system to two different 'rounds' that are not actually at the same a.c. potential. This unbalances the line impedances. Ground-cancelling outputs would appear to be very suitable for hi-fi use, as they are an economical way of making ground-loops innocuous. Quasi-floating outputs use a rather subtle circuit with an intimate mixture of positive and negative feedback of current and voltage.
