Dangerous Music 2-Bus Manual
7
Balanced Audio Connections
The beauty of balanced connections is that they promote the idea that current should be
prevented from flowing down cable shields while letting the audio pass. Pins 2 and 3
carry a signal across them (transverse mode) and any interference that gets through the
shield is picked up equally by the wires (common mode). The common mode noise is
canceled by the differential action of the instrumentation amplifier in the first stage of the
2-Bus. Signal gets through and the grounds stay put inside their respective pieces of gear.
Unbalanced Audio Connections
An unbalanced source driving a 2-Bus input usually presents no problem because
of the differential action of the input stage.
It is a good idea to use 3 wire cables even in an unbalanced situation because the
2-Bus input can keep stray noise away from the signal even without the benefit of
common mode rejection. If an unbalanced source gives one trouble, then this is usually
because the source doesn’t have a proper ground reference. This is why there are
Input
Shield Lift
jumpers inside the 2-Bus (and many other pieces of professional audio gear).
