Phonic MM1002a, Руководство пользователя

Страница: 7 / 20

PHONIC CORPORATION Page 7 MM1002a/1202a USER’ S MANUAL
UNBALANCED & BALANCED
Most of the mistakes in audio installations are due
to incorrect and/or defective audio connections. In
order to perfectly complete your installation, please
pay special attention to the following section unless
you are already familiar with balanced/unbalanced
operations.
WHAT IS AN UNBALANCED LINE?
You can find this kind of system in most of home
audio-video systems. They have one conductor to
carry signal, and another conductor for a ground.
Normally, for lower level signals, the ground con-
ductor shields the signal conductor.
WHAT IS A BALANCED LINE?
A balanced system transmits signal via two con-
ductors plus one ground shielding conductor. The
two signal conductors carry the same signal but out
of phase. For the balanced input stage, the ampli-
fier will boost the difference between the two signal
conductors and remove the identical part (known
as common mode signal) of the two signals. Be-
cause the real signal is carried by the two conduc-
tors out of phase, so it is perfectly carried to the
input. At the same time, interference that occurs
during transmission will be identical (common
mode). Because the signal conductors are run to-
gether, there is no chance they can be different,
and all the interference will be removed by the bal-
anced input amplifier.
THE DIFFERENCE BETWEEN TWO
OPERATIONS
Because of the common mode interference immu-
nity of a balanced system, the ground conductor
does not need to carry any electrical current, which
means the ground of the two connected units has
an identical ground level which is vital to an inter-
ference free system. Let us look back at the unbal-
anced system. The signal electrical current goes
from the signal conductor to the ground conductor.
The ground level of the two connected units are not
identical. This means the system is more easily in-
clined to noise interference.
Running long cables is easy for a balanced system
but difficult for an unbalanced one. A Lower noise
level is a characteristic of a balanced system.
Because a balanced system needs two conductors
for the signal and one conductor for the ground, a
minimum of three conductors are needed for wir-
ing a balanced system. Therefore, a dedicated sys-
tem separates the ground and shields the two con-
ductors.
Please read following section to properly wire for
balanced and unbalanced systems:
THE CORRECT WIRING FOR BALANCED
OPERATION
Always connect the main power with three plugs.
Make sure the power system ground is working
properly. Do not use a ground insulator plug adapter
without properly connecting the ground individually.
This is vital to making a successful audio system
connection.
Always connect the ground pin (PIN 1 in XLR) to
the source unit, and disconnect this pin on the des-
tination unit. This connection topology is to avoid
creating a grounding loop between the signal and
power ground. Utilize only the power ground, be-
UNBALANCED & BALANCED