Sunfire XTEQ8 User Manual page 21

Hum
Adding any component such as a subwoofer
to an existing system will often give rise to
a hum which wasn't there before. Your first
thought may be that the subwoofer has a
problem, but this is more than likely caused
by a "ground-loop" in your system.
Follow these steps to isolate the main cause
of the ground-loop hum (there may even be
more than one cause).
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Try to have all of your equipment on
the same electrical outlet or circuit, see
page 9 for more details.
If your subwoofer is a fair distance
away from your other equipment, you
may use a 15 amp extension cord as
long as it has a ground connection.
NOTE: Never remove the ground
pin from any power cords. This is
very dangerous.
Turn off all components in your system,
including the subwoofer, amplifiers and
the preamplifier, before disconnecting
or connecting cables.
First remove every connection from the
subwoofer to the rest of your system.
Plug the subwoofer power cord back in
and check for the hum. If it is still there,
try plugging it into a different outlet in
case it is picking up interference on the
AC line.
If you have followed the above
guidelines for the power connections
and a hum is still present, then there
is one very common problem to
consider: a "ground-loop" introduced by
connecting a cable TV line to a DVD or
blu-ray player, which is then connected
to the preamp. This can be addressed
as follows:
Disconnect all cables which come
from outside the room, such as cable
TV, satellite TV, or roof top antennas.
Make sure that they are disconnected
User's Manual
where they first enter the room, so
they are making no connection to
your preamplifier, TV, or any other
component. If the hum is caused by
the cable TV line, then you will need
a "ground-loop isolator." This is an
inexpensive device fitted in line with the
coaxial cable feed.
• If the hum persists, disconnect all the
source components one at a time from
the back of the preamplifier until you
identify the problem.
• Ground-loop isolators are available
for audio lines and video. Once you
have identified which components
are causing a problem, you can fit the
isolators between the component and
the preamplifier.
No Auto Turn-off
The subwoofer should go into standby mode
after approximately fifteen minutes with no
audio signal present. If not, check there is
no background hum. The subwoofer may
sense hum as a small signal and stay on.
See the above hints to eliminate the hum.
No Auto Turn-on
The subwoofer should turn on (come out
of standby mode) when an audio signal is
applied, or 12 VDC is applied to the Trigger
inputs, or if the Start button is pressed. If it
does not then, check the following:
• Check that the subwoofer power switch
is on.
• The subwoofer's volume control
may be turned down, or no signal is
received from your preamplifier.
• Check the input connections.
• Check the mode switch or menu on
surround systems to be certain that
a bass signal is being sent to the
subwoofer.
• Use the 12V Trigger for the most
reliable on/off operation.
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