Page 1
Hum Eliminator™ INSTRUCTION MANUAL
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
and noisy single coil pickups, a noise gate is the proper solution.
USING THE HUM ELIMINATOR™
Identify the ground loop causing the trouble; 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, such as the mixer, 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 (making sure all
grounds are connected and in good condition) then listen for hum or noise.
3) Turn on and off the power each time you switch equipment to avoid pops/shorted outputs.
4) Proceed until you find the offending piece(s) causing the problem.
5) Plug the Hum Eliminator™ in all lines between the offending equipment and the rest of
the system. For example, insert the line outs of the keyboard into the inputs of the Hum
Eliminator™, then insert the line outs of the Hum Eliminator™ into the inputs of the mixer.
Note: Never use the Hum Eliminator™ between an amplifier and speaker or the
equipment may become damaged. Use only on non-powered line level signals.
With a rack of amplifiers, we recommend putting an 8 channel single rack space Hum
Eliminator™ 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
but you should also try isolating the chassis from the rack with electrical tape and insulating
the rack screws with nylon washers.
Most ground loop problems can be solved using the Hum Eliminator™. Patience is a necessity
when attempting to solve ground loops! 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.
EBTECH® Hum Eliminator™ Applications
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 true balanced signals.
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) 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, 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.
MIXERS/RECORDING - Many mixers have either unbalanced or "impedance balanced" monitor
outs / aux sends. Use a Hum Eliminator™ to get true balanced monitor outs for noise-free performance.
When using more than one mixer (or submixing), there's a huge chance of getting ground loops
(and that buzz!). Use Hum Eliminators™ to prevent these ground loops. Eliminating hum is one of the
biggest challenges facing studios. Many studios will run all of their line level gear through Hum
Eliminators™ to help ensure noise-free recording.
KEYBOARDS / SAMPLERS / SYNTHS · Most keyboards, samplers, and synthesizers have unbalanced
-10dBV outputs. Use a Hum Eliminator™ to balance the signals if using with other -10dBV equipment.
To use a -10dBV unbalanced device with a +4dBu balanced device, use an EBTECH® Line Level
Shifter™ (see Page 5).
LIVE SOUND / DJ MIXERS - A common problem with live performance is long unbalanced cables
picking up hum along the way. Balanced signals are more immune to picking up noise. Use the
Hum Eliminator™ to balance long unbalanced signals. Mobile DJs or bands never know when setting
up their system if they're going to get a hum or not. The electrical wiring changes from one building
to another. What works fine at one gig might not work at the next. It's worth the low cost to
keep a Hum Eliminator™ available, nobody can afford to lose a gig because of hum problems. Some
DJs run everything in their rig through Hum Eliminators to play it safe. The main outs on most DJ
mixers are -10dBV unbalanced RCA. When using with a +4dBu power amp, over 2/3rd's of the
amp's volume can be lost. Use an EBTECH® Line Level Shifter™ (see pages 5, 6).
POWER AMPLIFIERS - Running multiple amplifiers can create ground loops between the amplifiers,
which will pick up the dreaded hum and buzz. Run each amplifier's input line through a Hum
Eliminator™ to prevent this problem.
GUITARS - Many guitar players use rack and pedal effects. They can get buzz from ground loops
that these devices create. Use a Hum Eliminator™ to eliminate that buzz. When using two or more
guitar amplifiers, ground loops can form between the amplifiers. Because of the tremendous amounts
of gain in guitar amps, the buzz can get so bad that the amplifiers will actually squeal (especially
with tube amplifiers). Simply run the feed to each amp through one channel of a Hum Eliminator™.
COMPUTER SOUND CARDS - Most sound cards have unbalanced inputs and 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™.
BROADCASTING / VIDEO - Press Boxes have many feeds all going to different gear; which can create
lots of ground loops and hum. Use a Hum Eliminator™ on these feeds to eliminate the problem. Using
a Hum Eliminator™ on the audio feed of a video camera can help prevent video hum (snow).
Loading...