Balanced and unbalanced connections

Mixing balanced and unbalanced systems

Since it is common even for professional installations to use unbalanced sound sources, particularly with musical instruments in live music sound applications, procedures must be followed to minimize the possibility of noise.

In general, commercially available devices can be used to convert high impedance and -10 dBV unbalanced outputs (typical for non-professional devices) to +4 dBV balanced, low impedance outputs (typical for professional use). Or the unbalanced inputs into balanced ones. These adapters should be placed as close as possible to unbalanced devices. In live sound applications, for example, it is still common to use "Direct Injection" boxes on stage to carry instrument signals along the entire length of the snake to a house (analog) mixer. Most digital mixing systems use stage boxes that digitize the signals, so they there are less prone to interference issues.

For connections made without this type of adapter, the recommended connection of an unbalanced output to a balanced input is illustrated in the diagram. Note that the negative and the sleeve (which does not connect to the input) are linked.