Reducing Intereference in Your Speakers? 59
PolicyWonk asks: "I just bought a new stereo, a Sony CMT-EP707, into which I intend to plug
my laptop when watching DVDs, and my iPod when listening to music. When I first turned the stereo on I was horrified to hear interference from a local radio station, as well as a general hum emanating from the speakers. The hum and the radio emissions are audible even when the stereo's volume is set to 'min' and irrespective of what setting the stereo is on (i.e. Tuner, CD, or MD), or what input is (or isn't) plugged into the stereo. (I have tried my laptop, iPod, and no input). That means that during a quiet pause in a movie, or the intro to a song, this background noise is clearly audible. No amount of moving the speakers around the room, or plugging the stereo into different grounded outlets seems to fix the problem. I've checked my outlets, and they appear to have a ground connection, but I live on the fifth story of a circa 1900 apartment building in Manhattan, so it's anyone's guess what happens to the wires once they are in the walls. Anyone have any good solutions for reducing or eliminating interference from nearby radio sources?"
RFI chokes (Score:5, Insightful)
Re:RFI chokes (Score:3, Informative)
Re:RFI chokes (Score:5, Funny)
Not all of us build our computer desks out of sawhorses and discarded dining-room doors.
- A.P.
Re:RFI chokes (Score:2)
What matters more, that it does the job or looks pretty? If you are going to prioritize style over substance, you've little grounds for complaint when performance is poor.
Re:RFI chokes (Score:2)
- A.P.
Re:RFI chokes (Score:3, Funny)
He already said he was using an Apple. No need to be redundant.
Re:RFI chokes (Score:3, Informative)
What they are is a ferrite core that makes a complete closed loop around the cable. Radio frequencies currents can't go through the middle - it blocks high frequencies. (If you want to get technical, the radio frequency current induces a magnetic field in the choke, and the change in magnetic field induces a voltage that exactly opposes the current.)
While strip magnets are made from a similar material, you simply cannot make it as effective as a proper choke.
On the other hand, the original question mentions hum - presumably AC 60Hz - and a choke will have negligible effect on a frequency that low.
Re:RFI chokes (Score:2)
I would hope not! Otherwise that choke would get real hot, real fast. The AC on that line is at 60Hz, and if the choke was actively "damping" that much current at that high of a voltage, it might be a Very Bad Thing.
Re:RFI chokes (Score:2)
Re:RFI chokes (Score:2)
I shouldn't post at whatever hour i posted that... oh well.
Re:RFI chokes (Score:1)
Go ahead- try and stick a ferrite suppressor to metal. Try even to stick a real magnet to a ferrite suppressor. Try looking it up on the web or even (gasp!) in the library.
But that might violate the precepts of the know-it-all. Actual research and testing.
How-To (Score:5, Informative)
Done. Now we can close this topic.
To quote google (Score:4, Funny)
Urg! (Score:3, Informative)
a) get someone in (professionally) to test the grounding
b) try turning off hotspot applicances, like microwaves, the fridge, air conditioners -- and then try it. More sensative equipment may pick up what less sensative equipment will not.
Oh, and a final though, do a google search on your sterio equipment in case there are others who have found this problem
Arghh! (Score:1)
Change the length of cable (Score:3, Informative)
Interestingly it only seems to happen in theatres
Re:Change the length of cable (Score:1)
Hmm. Not movie theaters, I hope...
Re:Change the length of cable (Score:1)
movie theatres are known as cinemas in the UK. Having said that we do film in one cinema - but its used for other things too
My Sony player does this too (Score:4, Interesting)
Re:My Sony player does this too (Score:1)
Re:My Sony player does this too (Score:2)
Re:My Sony player does this too (Score:2)
Meanwhile, my friends have all gone through at least one modern stereo component.
Re:My Sony player does this too (Score:2)
The CD player may just be dust, but the volume control is just low durability..
Building-related or warranty? (Score:2, Interesting)
Grounded Outlets (Score:3, Insightful)
I don't know but your landlord might be legally required to supply you with grouned electrical outlets.
A large block of copper (Score:2, Funny)
I have a similiar problem. (Score:2)
Re:I have a similiar problem. (Score:3, Funny)
you just complained about a Koss audio product.
Dear eMachines,
Did you know your computers are crap?
Sincerely,
Customer
Re:I have a similiar problem. (Score:3, Funny)
Dick.
The speakers (Score:1)
Ground Loop Isolator (Score:3, Insightful)
I bought an "Audio System Ground Loop Isolator" (# 270-054A) from Radio Shack for $20CDN... problem solved.
Here [epanorama.net] is a link to some info on the problem and possible solutions.
Powerlines (Score:3, Informative)
Nuder' (posible) solution (Score:2, Informative)
a) Moving your power and speaker cables further apart.
b) If they have to cross put them at a 90 degree angle to each other. This minimizes the effect.
This happened to me while I was doing sound back in High school and wireded me out until the band instructor told me about this. Same thing happened first night in the dorms in college, I thought it was my neighbors radio for the first two nights. (:
Re:Nuder' (posible) solution (Score:1)
Re:Nuder' (posible) solution (Score:1)
The speakers I have take shielded XLR mic cable for input. I had to assrig a connection one day and couldn't understand why the speakers were humming until I realized that the connection I made was unshielded. Tinfoil didn't work for me, so I just moved it away from the AC it was near and the hum went away.
Remember that power lines can carry signals, and with the old wiring in the building, I'm sure the problem could be 10 times worse than I'm used to dealing with.
RFI (Score:4, Informative)
The ARRL [arrl.org] has a web [arrl.org] page with some information on the subject.
You might ask the engineer at the local radio station for suggestions. Even though it is not the radio station's fault, he may be willing to offer some assistance. Local amateur radio clubs can also be sources of people who are willing to help.
Ask the support department of the manufacturer of your audio device for assistance. They may have technical bulletins on how to solve the problem.
If you are asking people for help, be nice, not confrontational. Remember that it is your audio equipment, not the radio station, that is at fault. Consumer electronic equipment manufacturers could avoid most of these problems by adding less than a dollars worth of parts to their equipment. Most do not, reasoning that it is cheaper to deal with some complaints of susceptibility to RF interference than to prevent the problem.
It's a green problem. (Score:2)
Anyway, many of the previous posters mentioned a few ideas that might help. One more thing to try though: it looks like the speakers are removable. Try disconnecting the speakers, then listening through the headphone jack. If the hum isn't there, attach the speakers and see if it returns. If the hum goes away with the speakers, then ferrite beads on the speaker wires MAY help. There is no guarantee though. The amps are probably not very carefully designed, and remember that a speaker coil has a lot of wire wound in it. That's not really a problem in FM, but remember that AM receivers use a lot of thin wire wound around a magnetic core...like a speaker. If this is the case, the speakers sound pretty cheaply made as well.
If the interfering station is AM, then you have an idea of where to try to fix this. Personally, the best solution seems to be returning the stereo. Find another model/brand, and if it doesn't have the annoying noise, the problem is solved. You can waste a lot of money on voodoo powerstrips and filters, and waste a lot of time fretting about the noise, wiggling different metal objects in the room, and twisting cables around just so. Just pack it up, take it back to the store, explain your problem, and say you'd like to try a different model.
On a side note, good quality speaker+subwoofer-only systems can be had for much less than $200. That would be my first approach to amplifying laptop and iPod audio. Check your store's computer section. I've never even paid for a set of computer speakers; one set came from a technical college that didn't want their bundled Labtec speakers; another set was free from a friend. Actually, on that last set I kept the subwoofer/amp section and threw away the cheap satellites...and used the speakers from a dead Sony bookshelf system. The sound is clean, and a bit more powerful than 15 watts per channel.
When I had this problem ... (Score:1)
I solved the problem by disconnecting the stereo from the common antenna and using my own antenna to receive radio.
Conclusion: Always use one ground only. Star/tree topology is a must for grounding. Never create loops.
Isolating from cable system (Score:2)
Try it and see. I bought 50 of each of those adapters, spent 20 minutes, and went door-to-door in my apartment complex asking if they had a problem with hum on their stereo system. Sold 'em for $3 apiece.
Bad filter capapcitors in power supply (Score:2)
If you bought it mail order then go to a couple of different friends places with it and try it there to see if location makes a difference. Even the specifications link doesn't say if this thing has to plug into the wall or if it can run on battery power, but if it can, see if using batteries instead of wall socket AC makes a difference.
E-mail me if you need further info or advice.
Take it back (Score:1)
As previous posters have said, electronic equipment should not emit radition, nor accept radiation. In most western countries, this is part of law.
If your speakers are accepting radiation, then chances are they may well be a source of unwanted radiation too.
I'm suprised that Sony would have such a design flaw, so I think the problem is specific to the actual speakers you have -- i.e. my guess is that they are broken.
Take them back for either exchange or refund.
Re:Take it back (Score:1, Informative)
You're wrong on with regards to the accept radiation.
From an FCC Declaration of Conformity:
Pursuant to Part 15 of the FCC rules. Operation is subject to the following two conditions:
(1) This device may not cause harmfull interference and
(2) This device must accept any interference that may cause undesirable operation.
CBers (Score:2)
Radio Signals and Concerts (Score:1)
If your laptop is a mac ... (Score:1)
Speaker Radio (Score:1)
During my ham radio training I learned a reason why this could happen. In many speaker systems you will find a crossover unit. This is basicly an inductor(coil) and a capacitor. This forms a tuned circuit that is designed to accept or reject signals of various frequencies. In som e cases the small amount of signal picked up by the speaker leads is enough to turn your speakers alone into radios.
I have even heard of rusty old fences "tuning in" to radio stations and amazing passers by.
btw, our local(Durban, South Africa) ham radio group set up a field station at the above mentioned light house a few years back. Forgeting about the beacon, they wondered why there were sparks between the antenna leads and a grounded bus bar on the desk. 1KW at 2m from your antenna can be rather scary.
Sounds like a ground loop (Score:1)