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10. TROUBLESHOOTING
10.1. Faults caused by external issues
Buzzing and hum in the speakers
Possible cause: multiple grounds
Hum in an audio system is often caused by several system components having their own separate
grounds. It is particularly common in systems containing tuners, VCRs or satellite receivers, as these
components are connected to an aerial. Because aerials and cables are always grounded, ground
loops can form between the aerial connection and other grounded equipment. Other equipment that
is normally grounded may include PCs with sound cards, and some CD/DVD players and DACs.
Although the V 40 SE is grounded, its signal ground is a "floating" ground, which means that the V
40 SE cannot itself create ground loops. Hum can only be caused when it is connected to other items
of equipment.
To fix the problem
Before trying to fix the problem, find out which of your system components is responsible for
generating the hum.
Procedure:
-
Unplug all source equipment, including any equalizer if used, from the V 40 SE, leaving only the
loudspeakers connected.
-
Reconnect the components back to the V 40 SE one at a time. As soon as the hum reappears,
you have two grounded components connected to the V 40 SE. You must now unplug your
components in reverse order to find out which of them is grounded.
Usually, the hum will still appear even when the problem components are switched off. The ground
causing the problem is always connected, since it is not broken when the power switch is operated.
Now that you know which components are grounded, you can discuss the problem with your dealer.
One option might be to use a signal-isolating filter on the aerials or cable networks. This devices do
not normally have any adverse effect on the sound or picture quality of tuners or TVs. Other possible
solutions could include using an isolating transformer or an isolating device offering complete
galvanic isolation. Please seek the advice of a specialist.
Power strips with built-in filters, mains filters or replacement mains cables are not appropriate
solutions.
Note
Switching power supplies are quite common nowadays. These are often fitted with a protective earth
terminal (PE) and an RFI filter. When using such units, the protective earth terminal
must
be
connected to the wall socket.
You must never remove this protective terminal, as doing so could
cause high levels of radio frequency interference to enter your system, which could affect the
operation of other digital equipment, including remote controls.
