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True to the Music
BASICS
What is a Mic Splitter
In modern concert production there are often two separate sound sys-
tems. The main PA covers the audience or "house" while a monitor sys-
tem covers the stage so the performers can hear. A third system may be
added if the concert is to be recorded. Each system requires it's own mix-
ing console because the mix that sounds good in the house simply won't
Stage Microphone
work for the monitors or be suitable for a recording. A mic splitter provides
the means to split the original signal from the on-stage microphones and
send it to the various systems, main PA, monitors, and recording, so that
each can get a clean, unaffected signal directly from the mic.
However, splitting microphone signals is not as simple as just wiring the
Isolation
microphones to all the consoles. Issues such as impedance loading,
ground loops and phantom power can degrade the signal and introduce
Transformer
noise. To solve these issues the 8ox uses high performance audio isola-
tion transformers to decouple the signal passing through it and eliminate
ground loops that cause hum and buzz in audio systems.
Inside A Transformer
A transformer consists of two coils of wire in close proximity to one
another wound around a metal core. One coil is the transformers input
(primary), the other coil is the output (secondary). A transformer is said to
electrically isolate, or decouple, the input from the output because there
is no physical connection between the primary and secondary windings.
When the primary winding is energized by the mic signal a magnetic fi eld
is produced and the lines of force cut across the turns of the secondary
Main PA
Recorder
Monitors
winding. Alternating current (AC) which makes up the audio program is
transduced from one winding to another through induction. Direct current
(DC) which is responsible for buzz and hum in sound systems, is blocked
by the transformer eliminating noise caused by ground loops.
Those Darn Ground Loops
A ground loop is created when an audio system has multiple paths to ground, often called earth. This situation can occur when two
AC powered audio devices, such as two mixing consoles, are plugged into different power circuits and connected together via a signal
cable. Both audio devices have a path to ground through the third prong on the AC-mains cable. The signal cable completes the loop
by connecting the devices together through the signal cable's shield.
Transformer Isolation
Earth
Earth
Once the loop is complete there is the electrical potential for DC voltage to fl ow through it. This potential is caused by the interaction
between devices with different ground voltage references and allows unwanted spurious current to fl ow through the shields of the
signal cables. This fl ow of DC voltage creates noise in the signal wires through induction and capacitance at the base frequency of 50
or 60 Hz (hum) and the upper harmonics of 120 Hz, 240 Hz, etc. (buzz). Isolating or decoupling the audio signal with a transformer at
a point between the two devices is the best way to block the unwanted fl ow of ground-potential currents and eliminate hum and buzz
in audio systems.
Sound Quality
Besides isolation to prevent hum and buzz, audio transformers must sound brilliant and sound quality is what sets Radial transform-
ers apart. Designed for pro-audio applications they include a host of features not found in general purpose audio transformers. A core
material of nickel-iron allows ultra high input levels before saturation, linear frequency response, excellent bandwidth and near zero
phase distortion. Consistent unit-to-unit performance is achieved through precision computer controlled winding. The core is sealed in-
side a mu-metal can which provides enhanced shielding from electromagnetic interference. The built in Bessel low pass fi lter removes
ultrasonic distortion that can mask natural sound and cause ear-fatigue.
2
Radial Engineering Ltd.
8ox & 8cx Owner's Manual
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