“Hum” Noises in the Speakers
This problem is more than likely caused by a “ground loop” in your system, rather than a fault in
the MA202R. Follow these steps to isolate the main cause of the hum, there may even be more
than one. Remember to turn off all components in your system, including the MA202R, before
disconnecting or connecting any cables.
Ground loop isolators for audio lines and video devices are available from you CARVER Dealer.
Although this is not always an ideal solution, the grounding differences between certain home
entertainment components sometimes require ground loop isolators. Ths is the exception rather
than the rule.
Other Probable Causes of Noise
Speaker noise may also be caused by interference or noise on your AC line. Make sure there are
no large appliances sharing the line, or halogen lamps or light-dimming Triac devices.
If you have very high efficiency speakers, these may tend to reveal noises which other speakers
do not.
Remember to turn off all components in your system, including the amplifier, before disconnecting
or connecting any cables during troubleshooting.
Try to have all of your equipment on the same electrical outlet or circuit. Group all the low power
components (preamp, CD player, DVD etc.) on a single outlet or power strip. This is provided that
the overall current draw from your equipment does not exceed the rating of the outlet or breaker.
Disconnect all cables which come from outside the room, and check if the hum goes away. This
includes such connections 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 the preamplifier
or the TV, or any other component. lf 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.
Contact your cable company or your CARVER Dealer for assistance.
Disconnect all connections from the preamplifier to your TV, VCR or DVD.
As a test, disconnect any other component which has a grounded power cord. Never remove the
ground pin from any power cords (if present). This is very dangerous.
If the hum persists, disconnect all the source components one at a time from the back of the
preamplifier, until you identify the problem.
Try moving the speaker cables away from any power cords. Try just one speaker, connecting it to
each amplifier channel and see if one channel is bad.
Check that the interconnect cables to the amplifier do not have any broken connections. The best
way to do this is to substitute a known good connection for the suspect connection. lf you reverse
the cables and the problem goes away, the cable may be damaged or broken. This is possible even
if you can’t physically see the break as the strain for pulling on audio cables can sometimes break
the wire internally.
Try connecting your system to another AC socket on a separate line.
If the hum is heard from within the MA202R and not through the speakers, this may also be caused
by interference on the AC or DC lines. The power transformers may turn this interference into
an audible noise. Internal hum can be made worse by a shelf or cabinet resonating, so try moving
the MA202R to another shelf.
Try moving your components further away from the TV, especially if you ever notice the screen
has changed color in the area closest to the component.
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