MORLEY Hum Eliminator

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Hum Eliminator™ User Instructions

Silence AC Hum, forever! Do you hear a hum or buzz in your audio signal? Are long unbalanced lines across stage creating

noise problems? Get the Hum Eliminator™ from Morley®.

Almost all AC hum (60Hz in the US, 50 Hz in most other countries), is caused by ground loops. These ground loops act like

radio antennae picking up hum and noise. The Hum Eliminator™ completely eliminates this by breaking the ground loop,

making it impossible for the signal lines to pick up the AC hum and noise in the first place.

Just plug the Hum Eliminator™ in the signal lines between the offending pieces of equipment and you’re done! Quick and

easy. No buzz, no hum. No signal degradation. No filtering. No noise gates. No dangerous ground lifts.

• Eliminates AC hum / 60Hz buzz and noise, quick and easy

• Breaks ground loop safely, while leaving all signal grounds intact

• Automatically translates signal voltages to match differences in

ground potentials, avoiding clipping

• Converts automatically back and forth between balanced and

unbalanced lines at either end

• Morley Engineered Custom 1:1 Isolation Transformers

• Completely passive design with audiophile quality components

assures the best possible performance

• Frequency response 20Hz to 70kHz plus or minus 0.5dB

• Distortion less than 0.005% THD @ 1kHz

• Crosstalk better than –97dB

• Maximum source impedance 1kOhm. Minimum load impedance

10kOhm

• Cold Rolled Steel Housing

• One Year warranty

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.

Need help?

Do you have a question about the MORLEY Hum Eliminator and is the answer not in the manual?

Summary

Getting Started with Hum Eliminator

What Hum Eliminator Solves

Explains the Hum Eliminator's purpose as a unity gain isolator for breaking ground loops and eliminating hum.

Using the Hum Eliminator

Provides step-by-step instructions for identifying and resolving ground loop issues using the Hum Eliminator.

Common Uses for Hum Eliminator

Ground Loop Prevention

Details how the Hum Eliminator prevents AC hum and noise by breaking ground loop antennae.

Signal Conversion

Highlights the device's role in cost-effectively converting unbalanced signals to truly balanced signals.

Live Sound and DJ Applications

Explains its use for preventing hum from long unbalanced cables in live sound and DJ setups.

Studio and Recording Use

Covers using the Hum Eliminator for noise-free performance in mixers, recording, and studio environments.

The Morley Hum Eliminator™ is a passive, unity gain signal and ground path isolator designed to eliminate AC hum and buzz caused by ground loops in audio signals. It achieves this by breaking the ground loop, preventing signal lines from picking up AC hum and noise.

Function Description:

The primary function of the Hum Eliminator™ is to safely break ground loops without degrading the audio signal. Ground loops, which often act like radio antennae, pick up 60Hz (in the US) or 50Hz (in other countries) AC hum and harmonics broadcast by a building's electrical current. By inserting the Hum Eliminator™ in the signal path between offending pieces of equipment, it makes it impossible for the signal lines to pick up this AC hum and noise.

Beyond hum elimination, the device also offers several other key functionalities:

Signal Voltage Translation: It automatically translates signal voltages to match differences in ground potentials, thereby preventing clipping.
Balanced/Unbalanced Conversion: The Hum Eliminator™ automatically converts signals back and forth between balanced and unbalanced lines at either end, making it a cost-effective way to achieve true balanced signals from unbalanced sources. This is particularly useful for longer cable runs where unbalanced signals are more susceptible to electrical noise and RF interference.
Isolation: It utilizes Morley Engineered Custom 1:1 Isolation Transformers to provide complete isolation, ensuring signal integrity.

Important Technical Specifications:

Design: Completely passive, audiophile-quality components.
Frequency Response: 20Hz to 70kHz, plus or minus 0.5dB.
Distortion: Less than 0.005% THD @ 1kHz.
Crosstalk: Better than -97dB.
Maximum Source Impedance: 1kOhm.
Minimum Load Impedance: 10kOhm.
Housing: Cold Rolled Steel.
Warranty: One Year.

Usage Features:

The Hum Eliminator™ is designed for quick and easy use. Simply plug it into the signal lines between the equipment causing the hum. It works on line-level signals (+4dBu or -10dBV) and is not intended for use between an amplifier and speakers, as this could damage equipment.

Common Applications:

General Hum/Buzz Elimination: Solves hum and noise caused by ground loops in various audio setups.
Broadcasting/Video: Eliminates ground loop issues in press boxes, broadcast studios, and can prevent video hum (snow) and hum bars from video cameras.
Computer Sound Cards: Balances unbalanced inputs/outputs and resolves buzz caused by computer power supplies.
Guitar/Bass Rigs: While the Morley Hum X is recommended for guitar/bass ground-related hum, the Hum Eliminator™ is an alternative, especially for FX pedals with 3-prong ground plugs or when using multiple amplifiers with stereo FX or ABY splitters. It also addresses DI connection hum to the PA.
Home Theaters: Addresses hum and buzz in audio caused by ground loops from multiple components with three-prong grounded plugs, and can eliminate Video Hum Bars.
Keyboards/Samplers/Synths: Balances unbalanced -10dBV outputs for use with other -10dBV or +4dBu equipment.
Live Sound/DJ Mixers: Balances long unbalanced cables to prevent hum, especially in unpredictable venue electrical environments. It's recommended for DJs to run their entire rig through it for safety.
Mixers/Recording: Provides true balanced monitor outs for noise-free performance from unbalanced or "impedance balanced" mixer outputs/aux sends. Prevents ground loops when using multiple mixers or sub-mixing, and helps ensure noise-free recording in studios.
Power Amplifiers: Prevents ground loops between multiple amplifiers.

Troubleshooting and Setup:

To identify the source of a ground loop:

Strip the system down to the mixer, disconnecting all interconnects and AC cords except for the mixer.
Add one piece of equipment at a time, hooking up AC and interconnects, then listen for hum or noise.
Turn power on and off each time new equipment is added to avoid pops/shorted outputs.
Continue until the offending piece(s) causing the problem are found.
Insert the Hum Eliminator™ on all cable connections between the offending equipment.

Important Considerations:

Not all ground loops cause noise or hum.
The Hum Eliminator™ will not reduce hum or noise normally generated by a piece of equipment itself (e.g., noisy preamps, single-coil pickups, faulty tubes).
For complex systems, patience is required to diagnose ground loop causes.
When using a rack of amplifiers, multiple Hum Eliminators™ in front of amp inputs are recommended.
If a common ground loop path is through a chassis into a rack, try isolating the chassis from the rack with electrical tape or insulating rack screws with nylon washers in addition to using the Hum Eliminator™.
For mixers with TRS balanced line inputs that lack common mode rejection (dropping the inverted signal to create unbalanced inputs), running a balanced line into the Hum Eliminator™ and then a mono 1/4" line from the Hum Eliminator™ outputs to the mixer's TRS inputs can preserve common mode rejection.

Maintenance Features:

The device is completely passive, meaning it does not require external power or complex maintenance. Its cold-rolled steel housing provides durability. The one-year warranty covers potential manufacturing defects. No specific user-level maintenance is detailed beyond proper usage and avoiding misuse (e.g., connecting between power amp outputs and speakers).