MORLEY Hum Eliminator User Instructions

GETTING STARTED
WHAT WILL THE HUM ELIMINATOR™ SOLVE? The
Hum Eliminator™ is a unity gain signal and ground path
isolator designed to break ground loops. Hum and noise
caused by the presence of a ground loop can be stopped
by inserting the Hum Eliminator™ in the line level signal path
(+4dBu or -10dBV). This eliminates the ground loop without
degrading your signal. The Hum Eliminator™ will not
reduce hum or noise normally generated by a piece of
equipment. In other words, for noisy preamps, noisy
single coil pickups or noise caused by faulty tubes, other
corrective action would apply.
USING THE HUM ELIMINATOR™: First, identify the
cause of the ground loop. Note: not all ground loops cause
noise or hum. For complex systems, you may need to
repeat these steps starting with a different piece of
equipment in various combinations to locate the problem:
1) Strip the system down to one piece, by disconnecting all interconnects and
AC cords except for the mixer.
2) Add one piece of equipment at a time; hook up AC and interconnects
then listen for hum or noise.
3) Turn on and off the power each time you add equipment to avoid pops /
shorted outputs.
4) Proceed until you find the offending piece(s) causing the problem.
5) Insert the Hum Eliminator™ on all cable connection between the
offending equipment.
Note: Never use the Hum Eliminator™ between an
amplifier and speaker or you will damage your
equipment. Use only on non-powered line level
signals.
With a rack of amplifiers, we recommend putting
multiple Hum Eliminators™ in front of your amps inputs so
you do not have to solve ground loop problems during
sound checks. A common path for ground loops is through
a chassis into the rack and then into another chassis.
Test this by removing the chassis from the rack. The Hum
Eliminator™ will help this problem but you should also try
isolating the chassis from the rack with electrical tape or
insulating the rack screws with nylon washers. Most ground
loop problems can be solved using the Hum Eliminator™ but
patience is a necessity when attempting to diagnose the
cause of ground loop! Many popular mixers with TRS
balanced line inputs do not have common mode rejection.
They drop the inverted signal, creating unbalanced inputs!
To get the benefits of balanced inputs, run your balanced line
into the Hum Eliminator™ and run a mono 1/4" line from the
Hum Eliminator™ outputs to the mixer's TRS inputs. This
way you are running a balanced line all the way up to the
Hum Eliminator™ and you will not lose common mode
rejection.
COMMON USES FOR HUM ELIMINATOR
The Hum Eliminator™ does more than just prevent AC hum
from being picked up by your sound systems. It also can be
used as one of the most cost-effective ways to convert
unbalanced signals to truly balanced signals. On the
Morley® Hum Eliminator™, you can use the 1/4" and XLR
jacks in any combination.
GROUND LOOPS - The Hum Eliminator™ prevents ground
loop antennae from forming and picking up AC hum. AC hum
& noise is almost always caused by a loop antenna effect
across signal lines between two or more pieces of gear, or by
long unbalanced cables picking up noise. Loop antenna(e)
are basically a type of radio antenna, which tend to pick up
the 60Hz and harmonics (50Hz in other parts of the world)
AC signal being broadcast by a building's electrical current.
These loop antennae are closed circuits usually along the
ground wires and hence are commonly called ground loops.
BALANCED / UNBALANCED
Unbalanced signals are more susceptible to picking up
electrical noise & RF interference than balanced signals are.
The longer the unbalanced cable is the greater the chance of
a problem. The Hum Eliminator™ is one of the most cost-
effective ways to convert between unbalanced signals and
true balanced signals.
BROADCASTING / VIDEO - Press Boxes and broadcast
studios have many feeds all going to different gear; which
can create ground loops and hum/buzz problems. Use a
Hum Eliminator™ on these feeds to eliminate the problem.
Placing a Hum Eliminator™ on the audio feed of a video
camera can help prevent video hum (snow) as well as video
hum bars that are caused by ground loops.
COMPUTER SOUND CARDS - Most sound cards have
unbalanced inputs / outputs. Balance these with the Hum
Eliminator™. Even balanced sound cards have tremendous
susceptibility to ground loops because of the computer's
power supply. If you hear a buzz, use a Hum Eliminator™.
GUITAR OR BASS - Whenever possible, we recommend you
use our Morley® Hum X product for GROUND RELATED
hum issues on a guitar or bass rig setup. If you're in a part of
the world where the Hum X can't be used, the Hum Elimina-
tor™ is the next best solution. If any of your FX pedals have
a 3 prong ground power plug, you will need to put the Hum
Eliminator on the audio feed to the amp. When using two or
more guitar amplifiers (with stereo FX or ABY splitters)
ground loops can form between the amplifiers; place the
Hum Eliminator™ on the audio signal between the ABY and
the amp that is buzzing. Bass amps can get ground loop hum
from the DI connection to the PA; simply run that DI feed
through the Hum Eliminator™.
CONNECTIONS -