Grounding Hum and Noise

[LarryC]

Just noticed your post Larry, I have 3 dimmer switches in close proximity to my stereo, could it be as simple as upgrading those switches?

It sure worked for me.  They were wall paddle switches in my case, and the incandescent or halogen labeling was hard to see, stamped into the mounting flange of the switch. 

Edited February 12, 2015 by LarryC

[RT FAN]

 Thanks Larry, my contractor is at my house doing some work, I'll have him check it out for me, might as well have him put it on my tab.

[Arkytype]

Guys & Gals,

 

www.rane.com has written four Rane Notes that cover grounding, hum and RF issues when connecting audio gear. I've used these as a pocket reference for many years when solving hum, buzz and RF issues with broadcast and consumer audio products. Take the time to read them and you will solve your issues. Rane Note 110, Sound System Interconnection will probably solve 95% of your issues. If you scroll down to the bottom of each note, you can download the file as a .pdf

 

http://www.rane.com/note110.html

 

http://www.rane.com/note151.html

 

http://www.rane.com/note165.html

 

http://www.rane.com/note166.html

 

I'm not sure if it's covered in any of the notes but providing your gear with a balanced power source and a dedicated ground will almost guarantee a hum, buzz and pop-free audio/video system. I made my own balanced "power supply" using a 2 kw transformer mounted in a NEMA box. 

 

http://www.b-p-t.com/what-is-balanced-power.html

 

 

Lee

[Bubo]

 Thanks Larry, my contractor is at my house doing some work, I'll have him check it out for me, might as well have him put it on my tab.

 

Sometimes the best way to find a problem is to turn off entire circuits one at a time at the circuit breaker box until the problem goes away.

 

Try a dimmer switch sometime with a CFL bulb, somewhere outside with a foam extinguisher handy.

 

Turning everything off and leave just the microwave, then turn it on is a good one too. I don't have any in my home.

[westom]

 

 

Sometimes the best way to find a problem is to turn off entire circuits one at a time at the circuit breaker box until the problem goes away.

 

If RFI is suspected, a simple tool can identify it.  Take a portable AM radio tuned to some station maybe 100 miles distant.  This makes the receiver sensitive to RFI.  Then move the radio near suspect RFI sources,   Increased noise makes obvious anything that is creating RFI.

 

BTW, any computer with a defective power supply will also be an RFI source easily identified by that same radio test.

Edited February 13, 2015 by westom

[WMcD]

I moved into a house about 12 years ago that had a HUGE magnetic problem on one circuit. It was so bad that if a TV or monitor were placed on one bedroom wall, the screen would completely distort and become unviewable. I purchased a Gauss probe that fit my DVM. A ceiling fan had been installed by a previous owner and he mis-wired the neutral. 

This is also why a neutral should be pulled into every box, and is now required by code. Without a neutral wire to offset the magnetic field of the power wire, induction will produce a magnetic field. This magnetic field can cause all sorts of problems with electronics.

I recently had my Dad's house re-wired and the electrician did not believe a neutral was required. The guy was a joke as an electrician. I complained to the state and the city, but they just let it slide. I had to re-wire a lot of his work. Very sloppy and lazy electrician. This is the norm rather than an exception to the rule.

 

I wonder if you meant that ground should be pulled into every box, rather than neutral.

 

Just to give a little lesson:  Generally in AC wiring, there is at least a hot (black wire - think of death) and a white wire which is neutral.  It is the black, hot which carries the 120 volt 60 Hz voltage.  That is RMS volts which means that the peaks and valleys are 1.4 times more in magnitude.  The white is called a neutral.  It does carry the same current as the hot because it is in the circuit.  The neutral should be tied to a good ground at the service entrance.  So you have current flowing in a neutral wire with zero volts on it.

 

This does mean that only one of the wires (the hot, black) is carrying lethal voltage if properly wired.  This is the wire which should have a wall switch (if any) in series with it.  Putting a switch in the neutral circuit (switching the neutral) is a big no - no.  It works but the hot is still delivering the 120 volts RMS to the socket and any connected device.  If you get yourself between the hot and any ground, current will flow though you. 

 

- - - -

 

On hum and RCA connections.  In our amps, the input "sensor" responds to the difference between the chassis (sometimes called ground) and the center of the RCA connection.  So you'd say, the center conductor has no signal on it with no music and so my amp should be quiet.  But, the chassis ground could have a small amount of AC and the "sensor" reacts to it because the small amount of AC on the chassis is sensed as a difference between the center pin (which is at zero volts) and "ground" (which is not at zero volts).  

 

The small amount of AC can be not on your amp chassis, but on your receiver chassis and then you connect the two with the shield of the RCA. 

 

The best practice is to use star (central location) grounding all the chassis in the system. 

 

The use of cheater plugs to remove the ground is not good practice.  For example, two components have a ground lug on the cord and the chassis is therefore tied to house ground.  Then a third component is added which does not have a ground lug.  Hum results.  Rather than ground the chassis of the component, people use cheater plugs on the other two so that all the chassis are "floating" above ground.  Bad practice.

 

- - - -

 

Please don't think that 120 volts is not potentially lethal..  Fortunately for us, dry skin provides some resistance to current flow.  Wet skin less so.  But don't do anything but treat 120 volt AC with caution.  It can stop your heart.

 

WMcD

 

WMcD

Edited February 13, 2015 by William F. Gil McDermott

[Cut-Throat]

The best practice is to use star (central location) grounding all the chassis in the system.

 

In my particular case this was accomplished by plugging all of the components into the SAME OUTLET. Again, using different outlets all on the same circuit did not get rid of the ground loop hum.

Edited February 13, 2015 by Cut-Throat

[anarchist]

I had a couple issues in my home with hum or buzzing in a couple of different rooms.  Various attempts had not resolved it.  I was remodeling the house and needed to do some rewiring. 

 

That led me to the discovery of four issues: (1) Many grounds leading from the main panel connect to a copper water pipe, which is useless when the copper pipe leaves the house connected to pvc - do yourself a favor, verify you have copper pipe throughout or install a proper grounding system via rods driven into the earth; (2) a circuit was in place that had been clipped off and was no longer connected to anything other than air, unfortunately, it also had a retainer clip nail driven into it that was binding it to a live wire; (3) discovered another circuit was also compromised (nail through the wall pierced through it) and bound to the 2x4 studs; and (4) most outlets had been wired poorly by simply inserting the wire into the retaining clips (permitting them to move slightly or come lose altogether) rather then attaching them via the screw.

 

All grounding and noise issues have been resolved; in the one room it was entirely due to compromised circuit (I replaced the wiring), and in the other is was due to loose connections on the outlets due to the use of "insert wire here if you shouldn't be doing electrical work' wiring.

[anarchist]

 

The best practice is to use star (central location) grounding all the chassis in the system.

 

In my particular case this was accomplished by plugging all of the components into the SAME OUTLET. Again, using different outlets all on the same circuit did not get rid of the ground loop hum.

 

i would examine the wiring connecting the various devices on that circuit; of course, I have no hesitation in opening a wall to examine the root cause of a problem.

[Cut-Throat]

i would examine the wiring connecting the various devices on that circuit; of course, I have no hesitation in opening a wall to examine the root cause of a problem.

 

Believe me, that was done! ...... And that was the easy part!  .... My wall faces an unfinished part of my Basement. (My Shop) and the wall is always open! BTW - Electrical Wiring is not the only source of Hum and usually is NOT the cause of Ground Loop Hum.

 

As I had said in my original post in this thread, There are many causes and solutions to a Ground Loop Hum, applying other people's solutions to your system, will usually not work. You have to troubleshoot your own solution to your own system.

Edited February 13, 2015 by Cut-Throat