All studios, big or small can have problems with buzzes and hums.  These types of problems can quickly make the product put out by the studio unprofessional or even unusable.

These buzzes and hums come primarily from television broadcast signals that get into audio wires and equipment.  The interconnecting wires for the equipment have a shield that is supposed to be connected to "ground." The "connection to ground" literally means that the shield is connected to the earth we walk on.  This ground is "zero volts."  The idea is that a broadcast signal (or other stray signal) can induce buzz in the shield which "shorts out" the buzz.  See figure 1 below.  Home studios and professional studios alike get into trouble when grounds or shields are not used or not used properly.

The professional studio can spend a lot of money and effort getting "grounding" correct, but to do a half-way-decent job that works in 99% of the home studios is relatively easy.

Step 1: Establish Ground

The 3rd pin of a common household outlet is supposed to be "grounded." This ground is good enough for most small studios.  Sometimes the outlet is not wired correctly. To establish that you have a ground go to Radio Shack and purchase an outlet tester (about $15) and plug it in.  The instructions will tell you what lights are supposed to light if your outlet is correct. See figure 2, below.

If you have an older 2 prong outlet, buy a grounding adapter (about $1.00) and put the green wire or green tab under the screw that holds on the plate.  Then test the outlet.

Step 2 - Establish ONE Ground Source

In theory, any of the outlets in a building are supposed to have "0" volts on their ground pins.  NOT SO.  Most outlets have a small voltage (1/2 to 1 volt).  So it is important that the SAME ground be used for all of your equipment, including instrument amplifiers that are going to be used.  If different outlets are used for some of the equipment the, difference between the voltage on the ground pins of the two outlets can cause hum.

Use one outlet and a bunch of multi-outlet strips (these are about $7 at your building supply company).  Make sure everything goes back to the same outlet.  Your equipment does not draw a lot of power and 99.9% of the time you won't be tripping circuit breakers because of this.  Try to choose an outlet that doesn't have motor-driven appliances likes washers on the same circuit.

Step 3 - Check For Broken Wires

A piece of equipment can work with a broken ground wire but become an "antenna" for hum & buzz.  The third pin of equipment power cords connects the case of the equipment to ground.  One of the pins of the audio cables carries the shield.  

You can make a tester to check your cables by taking apart a flashlight (about $1) and taping some scrap  wire to the battery & bulb (as shown in the diagram).  Connect one wire to one pin of the audio connector at one end of the cable and the other wire to the same pin at the other end.  If the light lights, your connection is good.  For the 3rd pin on the power plug, connect the second end of your tester to the metal of the case on your equipment.

INSTALLING INSULATED & INSOLATED GROUNDS AT HOME

Step 1 of Debuzzing & Unhumming is to establish a good ground.  A professional studio would call in an electrician to install insolated and isolated ground plugs.  This would assure that the ground pins used in the studio were at or very close to "0 volts" with no stray hum.

The cost to the professional studio could be anywhere between $150 and $500 depending on circumstances.  At home you can install an insolated and isolated ground for your project studio that is as good as the electrician's, but for an out-of-pocket cost between $10 and $20.  

Why You Need A Good Ground

In theory, any of the outlets in a building are supposed to have "0" volts on their ground pins.  NOT SO.  Most outlets have a small voltage (1/2 to 1 volt). This is a high "line level" in audio. the same level as the audio signal you want.  As a project studio grows in capability, this poor ground starts introducing hum into the equipment.  The smaller project studios may not need a better ground now, but could well need one in the future.

Making A Insulated/Isolated Ground Adapter

A grounding adapter is sold in many hardware stores for about a dollar.  It is designed to provide a ground to a 2 wire outlet by attaching a grounding pit to the faceplate screw at the outlet  If the unit had instructions, it would say to attach the green wire coming out of the adapter to the faceplate screw on the outlet.   Figure 1, below shows this item.

We are going to modify this adapter so that the ground wire of the adapter attaches to a long wire that is properly grounded. The ground wire needs to be long enough to reach the nearest cold-water pipe.  If the wire is less than 25 feet away use a #12 green electrician's wire.   The local builder's supply outlet will sell this by the foot.  If the run is much more than 25 feet you should use a #10 wire.

You splice one end of the wire to the small ground wire of the adapter.  You can twist these wires together and solder + tape them.  You can also simply crimp them.  You will also buy from the builder's supply store a grounding clamp for pipes.  This will be attached to the other end of the wire. You then attach the grounding clamp to the cold-water inlet pipe to the water heater.

Even if you have a grounded outlet - use the adapter to give you an fully-insulated and isolated ground system

Copyright © 1998, 2003 by Robert Dennis - ALL RIGHTS RESERVED

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