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).

•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 connect- ing a cable TV line to a VCR or TV, 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 where they first enter the room, so they are making no connection to your preampli- fier, 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.

•If you are using the subwoofer’s Line Level inputs and there is a excessive amount of noise or hum present, using the Speaker Level inputs may yield a lower background noise level.

•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.

The subwoofer won’t turn off

•The subwoofer should turn itself off 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.

The subwoofer won’t turn 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 on surround systems to be certain that a bass signal is being sent to the subwoofer.

Audible snap from outlet

•When the subwoofer is initially plugged into the wall, there is an in-rush current surge as the power supply capacitors charge up. This may give rise to an audible snap from the outlet as the plug is inserted. This can be avoided by plugging the subwoofer into a switched outlet or switched power strip (rated at 15 Amps or more).

18 User's Manual