ATI Technologies AT4000 소유자 매뉴얼 - 페이지 10

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A Few Words About Hum and Noise

Audible hum, or a discernible low frequency noise, is one

of the most common problems in audio/video systems. This

hum, which may be present even when the volume is at a

low level, is usually caused by a problem known as "ground

loops". A ground loop occurs when there is a difference in

ground voltages between two or more components that are

connected electrically. This, in turn, creates multiple current

paths and causes the low-level noise, or hum.

While it is natural to suspect that the components in your

system are the cause of the hum, in many cases the cause

may be due to other conditions. In particular, cable TV con-

nections from outside the house have become a major source

of hum.

In most cases, one of the following suggestions should help

you to solve a hum problem in your system. Please try these

steps in the sequence shown, proceeding from one step to

the next if the prior suggestion does not eliminate the prob-

lem.

Potential Ground Loops

in a Complex A/V System

Suggestion #1:

To determine if a cable TV connection is responsible for the

hum, first turn all components off. Disconnect the cable TV

feed to your system at the first place where it connects to

your components. Alternatively, disconnect the cable TV

wire where it is connected at the wall outlet. Turn your sys-

tem back on, and listen if the hum has disappeared. If re-

moving the cable TV feed has eliminated the hum, contact

your cable provider and ask them to correct their cable

ground or insert a Ground Loop Isolator before reconnect-

ing the cable TV feed.

Suggestion #2:

Turn off all components in your system, and then disconnect

the input cables at the amplifier. Turn the amplifier back on,

and see if the hum is still present. If the hum disappears, the

fault may be in the input cables used. Try replacing them

with cables that have better shielding, and make certain that

the input cables are not running on top of any AC power

cords. Change the cables one at a time to determine if one,

or all cables is responsible. If the hum disappears when the

input cables are disconnected, but returns after the cables are

changed and the system re-connected, the problem may be

caused by your source device.

Suggestion #3:

Ground loop problems may also be caused by poor ground-

ing of the electrical system in your home, particularly when

there are multiple components with three prong, grounded,

power cords. Try unplugging these components one at a

time, and see if one or all of them is causing the problem.

The ultimate solution to this type of problem is to re-wire your

house with an isolated, star type grounding configuration. We

recognize, however, that this may be impractical and expensive.

In some cases, the use of an approved AC Power Isolation Trans-

former of sufficient capacity may solve this problem.

WARNING: If you suspect that the grounding system in your home's

electrical wiring is causing the hum problem, it is important that you do

not make any changes to the wiring yourself. Only a licensed electrician

should make any changes to household wiring, and they must be made in

full compliance with all local building, safety and electrical codes.

Suggestion #4:

Hum may also be caused by faulty earth grounds in your home's

electrical system. In the past, cold water pipes were often used for

the earth ground, so it is important to make sure that your ground

connection is still valid and has not become loose or corroded.

The cold water pipe method may no longer be valid in some loca-

tions due to requirements that the water meter be isolated from

the water mains with a length of PVC pipe, thus interrupting the

ground circuit. The safest, and most reliable, approach may be to

provide your own ground. This can be accomplished by having a

licensed electrician drive at least five feet of copper-jacketed steel

grounding rod into the earth, and using that for your grounding

connection.

Intermittent Hum or Noise

Hum that changes character or comes and goes is usually caused

by DC on the AC line. This can be caused by other devices in the

home like light dimmers or hair dryers or may be caused by prob-

lems on the electrical grid. If the hum persists after all of the

above suggestions have been tried, contact the ATI customer ser-

vice department for assistance. (323) 278-0001 x 112 or sup-

[email protected]

For Future Reference

Model Number________________________________________

Serial Number________________________________________

Date of Purchase______________________________________

Dealer Name_________________________________________

Dealer Address________________________________________

____________________________________________________

Dealer Phone Number__________________________________

Notes_______________________________________________

____________________________________________________

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