Phonic MU 1705, User Manual

Page: 8 / 24

PHONIC CORPORATION
Page 8
MU1705 USER’S MANUAL
UNBALANCED & BALANCED
UNBALANCED & BALANCED
Unbalanced & Balanced Connection
Most of the mistakes in audio in stal la tions are
be cause of incorrect and defective audio connec-
tions. In order to perfectly com plete your installation;
please pay special at ten tion to the following sec-
tion unless you are already familiar with balanced/
un bal anced operations.
What is an unbalanced system?
You can fi nd this kind of system in most of home
audio-video systems. They have one conductor to
carry the signal, and another con duc tor for a ground.
Normally, for lower level signals, the ground con-
duc tor shields the signal conductor.
What is a balanced system?
A balanced system transmits the signal via 2 con-
duc tors plus one ground shielding conductor. The 2
sig nal conductors carry the same signal but out of
phase. For the bal anced input stage, the am pli fi er
will boost the difference of the 2 signal con duc tors
and remove the identical part (known as co on mode
signal) of the 2 signals . Be cause the real sig nal
is carried by the 2 con duc tors out of phase, so it
is perfectly carried to the input. At the same time,
interference that occurs during trans mis sion will be
iden ti cal (coMUon mode). Because the sig nal con-
duc tors are run together, there is no chance they can
be different, and all the in ter fer ence will be re moved
by the balanced in put amplifi er.
The difference between 2 operations:
Because of the coMUon mode interference iMUu ni ty
of a balanced system, the ground con duc tor doesn’t
need to carry any elec tri cal current, which means
the ground of the 2 con nect ed units has an identical
ground level which is vi tal to an in ter fer ence free
system. Let’s look back to the un bal anced sys tem.
The sig nal electrical current goes from the sig nal
con duc tor to the ground conductor, and that means
the ground level of the 2 connected units are not
identical. This means the sys tem is much easierto
experience noise interference.Running long ca bles
is easy for a balanced system but dif fi cult for an
unbalanced system, and lower noise lev els are a
con stant characteristic of a bal anced system. Be-
cause a balanced system needs 2 con duc tors for the
signal and 1 conductor for the ground, a min i mum
of 3 con duc tors are need ed for wiring a bal anced
system. So a dedicated sys tem sep a rates the ground
and shields the 2 conductors.
Please read following section for properly wiring
bal anced and unbalanced systems:
The Correct Wiring for Balanced Op er a tion
Always connect the main power with 3 plugs. Make
sure the power system ground is working properly.
Don’t use a ground in su la tor plug adapter without
prop er ly connecting the ground individually. This
is vi tal to making a suc cess ful audio system con-
nec tion.
Always connect the ground pin (PIN 1 in XLR) to
the source unit, and disconnect this pin on the des-
ti na tion unit. This connection topology is to avoid
cre at ing a grounding loop between the signal and
pow er ground. Utilize only the power ground, be-
cause it al ways has a lower re sis tance and better
dis tri bu tion than the signal ground.
If there is hum, a possible reason is a bad ground
connection for the system. In case you can not fi nd
the fault, try connecting the ground pin of the input
connectors. If the hum is reduced or eliminated,
check your power ground ing system. Special at-
ten tion is needed when you use the equip ment
racks with some distance between them, and/or use
a large quan ti ty of power amplifi ers. Check the power
ground be tween the racks and power dis tri bu tion
strips with your elec tri cal supply engineer. Make sure
there is one, and only one, prop er ground point for
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