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I purchased an older house and when running some electronics i got a hum. Did some research and trial and error to figure out why What I came to realize its a ground problem in the old house. I have a new electrical panel so I'm up to code but the ground looks like its nothing more than a the copper line hooked up to the water pipes in the basement. My question 1...Could I knock a small hole in my basement floor and put in a grounding rod and switch the copper ground to use it? Question 2 ...would I need to cut the power to the house to safely do that? Thanks!!

  • Don't knock a hole. Borrow or rent a rotary hammer and drill just a 1/2" hole. I put mine under the basement stairs by removing the bottom tread. – isherwood Jun 21 '16 at 15:51
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If you get hum in audio electronics, it's almost certainly not the result of a poor electrical system ground. In fact, if your electrical system grounding conductors were all well-bonded but not grounded at all, your stereo would still be perfectly happy.

There are several much more likely potential sources for hum, mostly due to defective power supply filtering capacitors or power supply decoupling capacitors, "ground loops", capacitive, inductive, or common impedance coupling. Unfortunately, isolating the cause and curing it can be an adventure in debugging and diagnosis.

Older audio gear may have electrolytic or tantalum capacitors that have aged and dried out, or they may simply have failed, which reduces their capacitance and increases 60 Hz or 120Hz ripple in an audio component's power supply, causing increased hum. If your power amplifier or receiver creates hum in your speakers all by itself with no inputs attached or the input selector on an unused input, this can be the cause.

Ground loops are created when there is more than one ground path from device A to device B. The multiple paths form a loop, topologically speaking, hence the name. A ground loop is like a 1-turn transformer, and can couple stray magnetic fields from power conductors (or power transformers) at the 60Hz AC power frequency, which then results in a 60Hz current and voltage induced around the ground loop, which can impress itself on the "ground" of the unbalanced signal inputs in one of the devices, which you hear as hum. Ground loops can be difficult to deal with. Unplugging audio cables until the hum ceases, then replugging them one by one can point to a culprit ground loop.

Inductive (or magnetic field) coupling can occur between the magnetic fields of large power transformers (usually found in high power amplifiers) and sensitive magnetic devices like phonograph cartridges, magnetic tape heads, etc. This is why expensive audio gear will often have toroidal power transformers, which result in less stray magnetic fields and less likelihood of magnetic coupling.

Capacitive (or electric field) coupling can occur between high voltage waveforms (like 120V power line) and high impedance signal nodes (like the inputs of preamplifiers and even power amplifiers).

Capacitive and magnetic coupling is the reason quality electronics is packaged in metallic packages: a metallic conductive enclosure will act to prevent electric and magnetic fields from entering the enclosure (the Faraday effect) causing undesired coupling to sensitive signals. You can easily diagnose electric and magnetic coupling by physically separating audio components. The hum will decrease with increased separation.

Common impedance coupling occurs when an interfering signal (like AC power currents) flow in an impedance shared with another signal circuit, perhaps because of a small-gauge or poorly manufactured powerbar power cord shared by a large power amplifier and a preamplifier. Connecting large power amplifiers on their own circuit, or with their own large-gauge power cord into a different receptacle on the same circuit can benefit an audio installation suffering from common impedance coupling. Making sure the receptacle powering your audio equipment is the first on a circuit run from the electrical panel, and that the run is as short as possible, and no other appliances are on this circuit can also help.

Finally, making sure that the audio cables connecting your audio components are high quality, with good ground shield coverage, can minimize inductive and capacitive coupling to the signal conductors. Make sure that the connectors make good "ground" contact and are not oxidized or corroded (that's why the better ones are gold plated), so that the cable shields can be effective.

Whew. That's a long answer, and my fingers are cramping up. Hope it helps.

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Hums in audio electronics are generally not "ground problems" of the sort that'd be fixed by driving a ground rod. Instead, they're the result of such gremlins as miswired equipment that injects noise pickup onto signal references and poor filtering/rejection of the powerline. Using a filtering surge suppressor for your audio equipment can help send the noise back the way it came -- beyond that, it's a matter of hunting down sources of electrical noise and suppressing them, and making sure that noisy shields and such aren't bridged to signal references inside your cables or equipment (research the "pin 1 problem" if you want to know more about this).

As to putting a hole in your basement floor for a ground rod -- there's a good chance you'll have yourself a tiny spring in your basement if you do so. Better to go up and out instead -- and retain the existing water-pipe ground electrode, too, as your water system still needs to be bonded to the grounding system!

  • If there's hydrostatic pressure under the floor now it's almost certainly finding an exit. I doubt a new hole would change anything. – isherwood Jun 21 '16 at 15:49
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Do not punch a hole in your basement floor or you'll find out all about ground-water. If you want to add a ground rod, go "up" to exit the building at a convenient point, for instance the electrical service entrance.

There is no rule against having more than one ground rod. However the ground rods must be connected together by ground wires - you can't use ground rods as a substitute for ground wires (because earth doesn't actually conduct electricity all that well.)

Even if you think it's hokey, there is nothing wrong with using a water supply pipe for a ground "rod". Actually, Code is more favorable to water pipes than actual ground rods. If you want to use ground rods only, you either need to do an expensive test to confirm low resistance, or use two ground rods.

If you're going to remove a ground temporarily, then yes - you'll want to shut off main power. But even then, your "ground" is bonded to neutral in your main panel, and neutral goes to the transformer, so it could have some fairly significant "float" relative to ground, enough to kick your butt hard. I would rig a temporary ground around the work area, e.g. if you wanted to disassemble that water-pipe bond to clean it. Green Scotchbright pads are pretty good for cleaning up copper.

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Many homes have 2 grounds depending on where you are. I would not eliminate the existing ground but add a 2nd if you feel this is the right thing to do it can only help but not all noise issues are from weak grounds many are from electronics that create harmonics on the neutral. Most modern PC Power supply's, fluorescent ballast and dimmer circuits cause the "hum" you describe. Better grounds can help but may not eliminate the issue without RFI FILTERS that help dump the noise/ harmonics to ground.

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