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Tracking down
ground loop hum
Start with the
power amplifier
or receiver
Move down the
chain
Try each input
Cable TV can be
a culprit
4826 Sterling Drive, Boulder, CO 80301
PH: 720.406.8946 service@psaudio.com www.psaudio.com
Humbuster Manual.indd 4
Eliminating Noise
Tracking ground loop types of hums down is more difficult and below we have assembled some
helpful tips. At the end of the day it may make more sense to speak with your dealer for help.
The easiest way to figure out where ground loop problems lie is by the process of elimination. You
need to determine where the hum or buzz is coming from within your system. If it's a video hum
problem, use a known good source like a DVD player rather than cable or satellite. In video, it's
best to always assume that it's either a connection problem or, more likely, a cable problem. Our
experience has shown that poorly shielded video cables cause more hum problems than just about
anything else.
In an audio environment, the first suspect in the hunt would be the power amp or the receiver
that is driving the loudspeaker. To see if the power amp or the receiver is the culprit, turn them off,
disconnect its inputs and turn it back on again. Go back to the speaker and place your ear in close
proximity to see if the hum is still there. If it is, then you have a problem with your power amp or
receiver and you should seek help from its manufacturer.
1. If the hum/buzz goes away when you remove the inputs to the power amp, your next step
will be to reconnect the amp and move further down the chain. If you have a preamp,
processor that is feeding the power amp, your next step would be to disconnect all inputs to
the preamplifier or processor. Once these are disconnected, and the preamp or processor is
connected only to the power amplifier, turn the system on and again, listen for hum. Should
the hum now appear, it is a problem with your preamp or processor or their interaction with
the power amp. Before returning the preamp or processor to the manufacturer, try a cheater
plug to break a ground loop. Cheater plugs are simple devices that convert a three prong
AC plug into a two prong AC plug and in the act of converting three prongs, to two prongs,
they disconnect the ground from the wall socket. Try one of these on the preamp, or the
power amp, or both. The same is true for a receiver or integrated as they have the preamp
built in to the amplifier.
2. If you determine that there is still no hum present when the preamp, processor or receiver
is connected with no inputs, then selectively begin plugging in your various inputs one at a
time. After each connection, check for hum until you discover the humming culprit.
3. VCR's, surround processors, and any device that is connected to a television cable or
satellite dish can cause a loud buzz and should always be suspect. If, by the process of
elimination described above, you determine it is a component like a VCR that is causing the
hum/buzz to occur, and using a cheater plug or removing the ground pin on a PS xStream
Power Cable doesn't help matters, it may be necessary to isolate the cable connection
(CATV) with an isolation transformer. This inexpensive device is available at most Wal
Mart, Radio Shack or department store type outlets and is sometimes called a 'matching
transformer'. If you have problems finding one, call your local cable TV company for advice.
The matching transformer will be placed between the cable TV input and the VCR, TV or
processor.
©2004 PS Audio International Inc. All rights reserved.
Owner's Reference
Humbuster III
Eliminating Noise 4
10/7/08 8:42:10 AM
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