Sonifex Pty Ltd T/A Innes Corporation
12/6 Leighton Pl
Hornsby, NSW 2077, Australia
Phone: +61 2 9987 0499
Fax: +61 2 9987 0599
E-mail:
Website: http://www.innescorp.com.au
13
Auricon 2.2+ Manual
Connecting the Auricon 2.2+ to Unbalanced Inputs and Outputs
Most professional audio equipment, including the Auricon sound card, uses high level balanced
audio interconnections. Commercial radio stations in Australia typically use a nominal
programme level of +8dBu, while the ABC, SBS and many production houses use +4dBu. In the
USA 0dBu is commonly used.
By contrast, domestic audio equipment uses low level unbalanced interconnections, typically at
a level of about 100mV rms (about -18dBu). The best way to interconnect between these two
systems is with a balancing amplifier. Failing that, it is still possible to achieve an acceptable
interconnection, particularly when going from a high level balanced output to a low level
unbalanced input.
In the diagram below, the transformer does the balanced to unbalanced conversion and the
resistors adjust the level. It is preferable to use a 1:1 transformer and the resistive attenuator
rather than a stepdown transformer as this will help minimise capacitive coupling of common
mode noise across the transformer windings.
Note that you should
never
ground one side of a balanced output. Doing so will most likely
damage the output drivers.
Going the other way from unbalanced to balanced is easy if the signal level is adequate. Simply
connect the balanced input across the active and earth of the unbalanced output. In most
cases, though, the level at the unbalanced output will be too low so you will need an amplifier. If
this is the case it is probably best to do the job properly and use a balancing amplifier.
Finally, note that the shields on the audio cables should only be connected at one end. In the
world of balanced audio, the shields are simply that - electrostatic screens - and should not be
used for earth returns.
Balanced
Output
Unbalanced
input
Unbalanced
output
Balanced
input
Shielded twisted pair
Shielded twisted pair
