Troubleshooting the Internal Amplifier of a Subwoofer

If a subwoofer is not outputting any audio, but is still showing an illuminated LED indicator, the first thing to check is the subwoofer's built-in amplifier.

Please Note: This is geared towards "home theater" subwoofers, not the subwoofers that come with our soundbars or computer speakers.

To do this, let's try something called a "buzz test":

1. Make sure the sub is plugged in, powered on and has a sub cable plugged into the LFE port on the back of the subwoofer
2. On the back of the sub, turn the gain knob up to at least 50-60% (about 12 or 1 o'clock on the dial)
3. Do not plug the other end of that sub cable into your receiver or sub output
4. Instead, grab the unplugged end of the cable and touch the male RCA post a few times to see if you can hear the sub give you a "buzz" sound each time you touch the post

HERE IS A PICTURED EXAMPLE OF A SUB CABLE WITH THE RCA POSTS HIGHLIGHTED

If you do not hear any buzz each time you touch the RCA post, then the built-in amplifier has likely gone out and will need replaced/repaired. If you are hearing the described buzz, the subwoofer should be capable of producing signal, and you will want to direct your attention to the AV receiver.

NOTE: If you get no audio from the buzz test, but still are getting LED response from the unit, it is possible an internal wire has come unplugged from the subwoofer amplifier.

IF YOU ARE COMFORATBLE DOING THIS, follow these steps to check the wires.

1. Unplug the subwoofer from the outlet
2. Remove the outside screws on the back of the subwoofer amp and pull the amplifier out of the subwoofer enclosure.
3. There should be two wires connecting from the amplifier to the round, cone woofer. Using your hands, make sure these wires are connected, secure and tight. 
4. Put the amp back into the subwoofer and screw it back into place. 
5. Plug in the power cable to the subwoofer and see if you are now getting audio when sending signal.

For steps on troubleshooting the cone woofer portion of the subwoofer, please see the article - Troubleshooting the Cone Woofer of a Subwoofer