Phonic MM1705a - Unbalanced & Balanced

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PHONIC CORPORATION

Page 8

MM1705a USER

’

S MANUAL

UNBALANCED & BALANCED

Unbalanced & Balanced Connection

Most of the mistakes in audio installations are be-

cause of incorrect and 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 system?

You can find this kind of system in most of home

audio-video systems. They have one conductor to

carry the signal, and another conductor for a ground.

Normally, for lower level signals, the ground conduc-

tor shields the signal conductor.

What is a balanced system?

A balanced system transmits the signal via 2 con-

ductors plus one ground shielding conductor. The 2

signal conductors carry the same signal but out of

phase. For the balanced input stage, the amplifier

will boost the difference of the 2 signal conductors

and remove the identical part (known as common

mode signal) of the 2 signals . Because the real sig-

nal is carried by the 2 conductors 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 con-

ductors are run together, there is no chance they

can be different, and all the interference will be re-

moved by the balanced input amplifier.

The difference between 2 operations:

Because of the common mode interference immu-

nity of a balanced system, the ground conductor

doesn’t need to carry any electrical current, which

means the ground of the 2 connected units has an

identical ground level which is vital to an interference

free system. Let’s look back to the unbalanced sys-

tem. The signal electrical current goes from the sig-

nal conductor to the ground conductor, and that

means the ground level of the 2 connected units are

not identical. This means the system is much easierto

experience noise interference.Running long cables

is easy for a balanced system but difficult for an

unbalanced system, and lower noise levels are a con-

stant characteristic of a balanced system. Because

a balanced system needs 2 conductors for the signal

and 1 conductor for the ground, a minimum of 3 con-

ductors are needed for wiring a balanced system. So

a dedicated system separates the ground and shields

the 2 conductors.

Please read following section for properly wiring bal-

anced and unbalanced systems:

The Correct Wiring for Balanced Operation

Always connect the main power with 3 plugs. Make

sure the power system ground is working properly.

Don’t use a ground insulator plug adapter without

properly connecting the ground individually. This is

vital to making a successful audio system connec-

tion.

Always connect the ground pin (PIN 1 in XLR) to the

source unit, and disconnect this pin on the destina-

tion unit. This connection topology is to avoid creat-

ing a grounding loop between the signal and power

ground. Utilize only the power ground, because it al-

ways has a lower resistance and better distribution

than the signal ground.

If there is hum, a possible reason is a bad ground

connection for the system. In case you can not find

the fault, try connecting the ground pin of the input

connectors. If the hum is reduced or eliminated, check

your power grounding system. Special attention is

needed when you use the equipment racks with some

distance between them, and/or use a large quantity

of power amplifiers. Check the power ground between

the racks and power distribution strips with your elec-

trical supply engineer. Make sure there is one, and

only one, proper ground point for the audio system

(or connected video system).

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Phonic MM1705a - Unbalanced & Balanced

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