Electricians, audible pop in speakers when lights on

Factual Questions
1

Hello, I have this problem in my home, it is a condo, 30 year old wiring, probably that old wire that was actually wrapped in cloth :slight_smile: Well, not that old, anyway… Every time a light switch is turned on or off, I can hear a audible pop go through various audio equipment in my home. For one, a set of 5 way speakers on my computer, through another speaker built into my mac, though it is very very slight. Those are the obly places I have noticed it so far.

It happens when I turn on the waster, dryer, dishwasher, certain lights, flourescents being the worst, and also when they are turned off.

This concerened me as I thought I was sending a surge of power to all my computer equipment. I had power strip surge protectors on all the computer stuff, but we all know those really do not do that much. I mean a lightning bolt may trip the littlr fuse, but I bet it still frys your stuff.

So next step to remedy this was to get a UPS, (uniteruptable power supply). I got one, anf let it charge up, and plugged the computer stuff into it and the speakers. Still had the pop, this made me mad, since the idea is that the equipment is running off of the battery at all times, not off the AC in the wall, and it should not allow one watt of power back through in the reverse direction. So, I unplugged the UPS from the wall, so now all the equipment was running off the battery, I could literally take all the stuff in the middle of a field and run it, so no AC power at all. Pop still happens!

I now feel a little better since I know that I am not sending any surge to the computer stuff, and add to that I will keep the UPS as a additional level of protection, but I can only conclude that the audio pop is a result of high RF coming from the start and stop of power transformers in certain equipment, maybe the balasts in a old flourescent light are no good.

So, I ask, how to fix, anything to worry about, can high RF hurt any uquipment, is the pop a bad thing? Do I have a open ground in my home etc?

As much detail from a qualified person is greatly appreciated

2

Scott, your UPS is a standby system. The inverter is only running during a power outage, othewise you are running your devices off line current. More expensive online UPS systems are always running from the battery/inverter so there is never a switch when the input volatge is interrupted. A power conditioner might help some of the transients you are seeing but might be worth it to replace a few of the old switches to see if it helps.

3

thanks padeye, but if you read a little more more closely I did account for this, but removing the UPS from the AC outlet, so that all equipment was for certain running off of the battery, any other ideas?

4

A UPS keeps power to your system when the AC goes kaput. That’s it. Filtering noise is not the primary purpose of a UPS, and you’ll find that cheaper ones don’t have much, if any. You’ll also find that the cheaper ones don’t put out a sine wave, but instead put out a stepped waveform with very little filtering that can itself cause noise problems. A UPS is also not a surge suppressor, although some may have surge suppression built in. Check the specs for yours.

There are also different types of power strips. Some have just a breaker, some have MOVs or the like to protect against surges. No matter what is in there, if a lightning bolt hits nearby it’s gonna go to power strip heaven. There aint much that can stop a lightning bolt. If it does actually have good surge suppression (which means it cost more than 5 bucks at wal-mart) then it’s designed to protect against, say, a lightning bolt that hits a mile away or so, and sends a nasty spike down the power line.

What you are hearing is a pop, which is electrical noise, not a surge, not a brownout. It may not be RF, a much lower frequency spike will produce an audible pop. Flourescent lights generate a lot of noise, including some RF components, so I’m not surprised that they are noisier.

I’m wondering if your ground isn’t really grounded, or the ground has degraded severely over the past 30 years. This is easy to do. I think 30 years ago they were still grounding through the water pipe, and then someone would come along and replace part of the water pipe with a piece of PVC and there went your earth ground. The ground could easily be degraded through other means though, that’s juse one of many examples. It could just be corrosion on a piece of copper wire that’s done you in.

I doubt that it will hurt any equipment. People who make electronic stuff have to account for heavy noise spikes, especially if you happen to live near the power distribution station. If you’re the type of person who likes to play their stereo REALLY LOUD then one of those pops could cause speaker damage (especially if the speakers are rated close to the max output of the amp, without much of a safety factor built in). However, since you are in a condo, and your neighbors haven’t booted you out already, I doubt that you have to worry about this.

I would however strongly suggest to your condo maintenance folks that they get a qualified electrician to take a look at it.

I’m really surprised that you still hear it in the computer when it’s running off of the battery. Have you tried disconnecting it from the phone line as well? In other words, if you still hear the pop when there’s no electrical connection into it, then it has to be airborn RF, which is not very likely.

5

These problems are hard to resolve, all right. I worked on consumer electronics for 12 years and taught amplifier theory for ten years before that and it still didn’t prepare me for all of the oddball things that can cause stray pickup noise.

There are always two problems. One, where is the RFI or EMI coming from? Two, what is the problem with the amplifier system that makes it susceptible to extraneous noise? Since you have eliminated the AC line, you know that the POP is certainly induced (inductively coupled, probably into the amp’s input circuitry. Try removing all input sources, like feeds from microphones & external sources. It could simply be that the audio circuitry has a poor ground inside the computer. Open the case and tighten any screws that appear to be used for grounding the circuit board to the chassis (don’t over-tighten!)

I once located a noisy light dimmer buy walking around my house using my bass guitar as a divining rod. The pickups allowed me to home in quite well.

Does your house have 3 wire AC? Are all outlets properly grounded? Get yourself one of these little gizmos that will test the integrity of the ground circuit in each outlet (but by god don’t pay $30 at Radio Shack for it!).

The fact that you get a POP when things are turned OFF really makes me think that the noise is being inductively coupled, since the collapsing magnetic field around a conductor will result in the same unwanted noise as an expanding one. Is there nearby household wiring (electrical service in the wall behind the computer, for example).

Without an oscilloscope & a suitable probe (sensitive to RF) it will not be easy to find the source of your POP.