Home Hacking: Tracking Down Speaker Hum

For a while now I’ve noticed an annoying hum coming from my home sound system, simply a Pioneer A400 connected to a Sony Blu-ray and our Samsung LCD TV. As today is lovely and sunny it seemed like the perfect opportunity to try and sort it all out. Hums in home hi-fi systems generally indicate bad earthing somewhere, the question is where. Time to get my geek debugging hat on.

First up – establishing that the hum is not coming from the amplifier. To do this I disconnected all external devices. Voila, the hum disappeared. That was a good start. Then I started to re-connect various devices to see when the hum returned, in this case it was when either the TV or Blu-ray were connected. Hmm. Why both? Perhaps my older amp doesn’t like these devices I thought.

Next up, I checked if the hum was being picked up from a power supply by the connecting wires. So all the wires came off and were routed round the front of the console. Nope, the hum was still there. Another possible cause removed.

Eventually I tracked down the source to the TV, as it turned out the blu-ray hum stopped when I disconnected the HDMI lead to the TV. This was more worrisome, as if the TV turned out to have a bad earth it would be expensive to get sorted out. Then I came across this handy post from CNET where the author suggests removing all your external coax/aerial connections.. voila! I removed our shared building aerial from the TV and the hum went away. Perfect. So now all we have to do is properly earth the aerial where it comes into our flat and the problem is solved for good. In the meantime though, removing the aerial so I can enjoy Inception in its full glory is a pretty easy workaround. Gotta love easy workarounds in the tech world. Of course this may not be the solution to your home speaker hum problem, but the main lesson here is isolate all possible causes in true Sherlock Holmes fashion, then you should be left with the culprit.