15
join (+insulate)
Balun
Balun
shield
1
2
3
XLR
RCA
3-Conductor Cable
Noise
s -AKESUREALLCONNECTIONSTOTHEACTIVESPEAKERS
are good.
s -AKESURENONEOFTHESIGNALCABLESAREROUTEDNEAR
AC cables, power transformers, or other EMI-inducing
devices.
s )STHEREALIGHTDIMMEROROTHER3#2BASEDDEVICEON
the same AC circuit as the SRM450v2? Use an AC line
filter or plug the SRM450v2 into a different AC circuit.
Hum
s 4URNTHE,%6%,CONTROLALLTHEWAYDOWN)FTHENOISE
disappears, it’s coming from the signal source. If not,
try disconnecting the cable connected to the INPUT
jack. If the noise disappears, it could be a “ground loop,”
rather than a problem with the SRM450v2. Try some of
the following troubleshooting ideas:
s 5SEBALANCEDCONNECTIONSTHROUGHOUTYOURSYSTEMFOR
the best noise rejection.
s 7HENEVERPOSSIBLEPLUGALLTHEAUDIOEQUIPMENTS
linecords into outlets which share a common ground
(see the diagram on page 13). The distance between
the outlets and the common ground should be as short
as possible.
Never remove the ground pin on the
power cord of the SRM450v2 or any
other component. This is very dangerous.
s 4HEHUMMAYAPPEARWHENUSINGANUNBALANCED
source (consumer preamp, CD player, VCR, etc.). This
is caused by the unbalanced-to-balanced interface
between the devices (and exacerbated by the fact
that most consumer audio equipment have a two-wire
linecord, without the third-pin safety ground).
Use an interconnect cable wired as shown below. The
important point is that the shield and the wire from the
XLR pin 3 are joined at the RCA (source) end.
s $ISCONNECTANYCABLESWHICHCOMEINFROMOUTSIDE
such as cable TV, satellite TV or roof top antennas. They
must be disconnected from every part of your system,
such as the TV, VCR and preamp. If the hum goes away,
you can add a “ground loop isolator” in your cable line.
This is an inexpensive device available from video or TV
dealers, or you can make your own from two TV baluns
(standard TV 75/300 ohm adapters):
The baluns are threaded at one end (75 ohm) to fit TV
coax cable and have two wires at the other end (300
ohm). They will not affect the video quality.
s )FTHEHUMPERSISTSTRYREMOVINGCOMPONENTSONEAT
a time from the back of the mixer or preamplifier, and
check for hum each time (turn off your equipment
before you undo any connections). It is fairly common
to find more than one problem.
s )FYOURPREAMPORMIXERARETHEONLYTHINGSCONNECTED
to the SRM450v2s and the hum is still there, try
different connection cables, or move the preamp/mixer
to another location.
s 0RESSINGTHE,/7#54&),4%2MAYHELPREDUCETHE
hum if you have trouble finding the cause of the
problem. Do this anyway if you do not need to
reproduce the lower frequency range.
