S

siper

Audiophyte
Guys, I'm stumped. I'm getting a spanish radio station blasting through my stereo on every input and in every speaker. There's a radio tower (AM, I think) that's about 500 yards from my house. I think narrowed it down to the speakers or speaker wire, but don't know what to do next.

Gear: Denon receiver, Polk Surrounds & Center, Canton Fronts

Speaker Wire I'm using

Steps I've taken:

  1. Ensure the outlet I'm using is grounded
  2. Tested with headphones. As I'm listening on my headphones, as soon as I start to unplug each speaker, the radio signal gets quieter and disappears when I unplug the last speaker cable.
  3. Ferrite Rings on ever speaker cable and power cable. Didn't have any effect.
  4. Shielding wire for the full length of a speaker cable. Didn't have any effect.
  5. Called Denon. They just told me to reset the receiver and if that didn't work, then I need to send it in for servicing. Reset didn't do anything.
  6. When I turn on the "Eco" function on the receiver, the sound goes away (but that essentially just turns off the surround speakers).
  7. Plugged in the radio receiver that came with the Denon. No effect.
Are there any experts out there that can help me before I throw everything away and buy a soundbar?
 
lovinthehd

lovinthehd

Seriously, I have no life.
Blow up the tower? :) I've read that twisted pair speaker wire can reduce the effect, since that seems to be your source, but never had the issue myself. That's really close to a powerful broadcast, good luck!
 
TLS Guy

TLS Guy

Audioholic Slumlord
Guys, I'm stumped. I'm getting a spanish radio station blasting through my stereo on every input and in every speaker. There's a radio tower (AM, I think) that's about 500 yards from my house. I think narrowed it down to the speakers or speaker wire, but don't know what to do next.

Gear: Denon receiver, Polk Surrounds & Center, Canton Fronts

Speaker Wire I'm using

Steps I've taken:

  1. Ensure the outlet I'm using is grounded
  2. Tested with headphones. As I'm listening on my headphones, as soon as I start to unplug each speaker, the radio signal gets quieter and disappears when I unplug the last speaker cable.
  3. Ferrite Rings on ever speaker cable and power cable. Didn't have any effect.
  4. Shielding wire for the full length of a speaker cable. Didn't have any effect.
  5. Called Denon. They just told me to reset the receiver and if that didn't work, then I need to send it in for servicing. Reset didn't do anything.
  6. When I turn on the "Eco" function on the receiver, the sound goes away (but that essentially just turns off the surround speakers).
  7. Plugged in the radio receiver that came with the Denon. No effect.
Are there any experts out there that can help me before I throw everything away and buy a soundbar?
This is a common problem when near a radio or TV tower. Yes, the speaker wires do act as antenae, and feed the radio signal back to the early high gain stages via the negative feedback circuit. This signal then gets rectified by the first semicondctor junction it meets and you the hear the station, as you have an amplified crystal radio!

Now I don't think those ferrite Rings will make any difference.

One thing is that you need to use twisted speaker cable, not what you are using. Belden 14 or 12 AWG is what you need. The cable you are using is the worst for this problem.

What I have done in the past when I lived close to the Crystal Palace TV tower many years ago, was to get some ferrite rods, and some 12 or 14 Gauge solid enameled wire and wrap 5 to 10 turns around the ferrite rods about 2" inches or so long and put them in series with the positive speaker leads right at the output from the amp.

Now you must scrape off the enamel from the ends you connect the speaker wire and the receiver. Use electrical tape to stop the coil unraveling and the rod moving through the coil.

In my case this did the trick. Now if this is not good enough then you might have to convert this set up to a tuned rejector circuit, by shunting your DIY inductor circuit with the right value cap.

If this is required you need to seek the assistance of the engineering staff of the radio station. Federal law requires operators of radio and TV stations to assist individuals suffering from these issues, in any reasonable way. If they refuse, then this old man can probably remember how to design a tuned RF rejector circuit once I know the radio frequency of the signal causing this problem.

The other thing that could be done, is to shunt the input junctions of the power amps with a tuned acceptor circuit. However, this would require know how and skills. I doubt you will find anyone willing to do this for you. I did have to do this in my case. It was not difficult as it was a tube amp.

This is another one of my beefs about receivers. The law requires that they have built in rejection of these unwanted signals. The lousy receiver manufacturers widely ignore this, to shave a few cents.

This is especially problematic because of LED light bulbs especially when controlled with SCR dimmers. These make a lot of RF, and you have to really wire your house to minimize it. This is a potent source of RF and causes hums and buzzes often confused with ground loops.

Lastly I have to be honest, that not all these cases can be solved. Some defy resolution, and the only remedy is then to move to a residence much further from the offending tower.
 
Last edited:
TLS Guy

TLS Guy

Audioholic Slumlord
Most of that information is not applicable to the OPs problem. Pickup of RF is not talked about nearly enough and is common. People just fail to see how the speaker cable can be the source of the problem because it is common. The only remedy mentioned for his problem is twisted speaker cable. I very much doubt that by itself will be a complete cure, but is a good place to start. Since his seems so severe I expect a rejector circuit might well be required.

Screen cable should not be used. But I do run my in wall speaker wire is large diameter steel conduit.



When I had the problem when I lived on Denmark Hill I could clearly see the Crystal Palace transmitter. I was initially baffled by it. I had a great education on it all from very nice people at BBC engineering. Their plans worked out.
 
S

siper

Audiophyte
This is a common problem when near a radio or TV tower. Yes, the speaker wires do act as antenae, and feed the radio signal back to the early high gain stages via the negative feedback circuit. This signal then gets rectified by the first semicondctor junction it meets and you the hear the station, as you have an amplified crystal radio!

Now I don't think those ferrite Rings will make any difference.

One thing is that you need to use twisted speaker cable, not what you are using. Belden 14 or 12 AWG is what you need. The cable you are using is the worst for this problem.

What I have done in the past when I lived close to the Crystal Palace TV tower many years ago, was to get some ferrite rods, and some 12 or 14 Gauge solid enameled wire and wrap 5 to 10 turns around the ferrite rods about 2" inches or so long and put them in series with the positive speaker leads right at the output from the amp.

Now you must scrape off the enamel from the ends you connect the speaker wire and the receiver. Use electrical tape to stop the coil unraveling and the rod moving through the coil.

In my case this did the trick. Now if this is not good enough then you might have to convert this set up to a tuned rejector circuit, by shunting your DIY inductor circuit with the right value cap.

If this is required you need to seek the assistance of the engineering staff of the radio station. Federal law requires operators of radio and TV stations to assist individuals suffering from these issues, in any reasonable way. If they refuse, then this old man can probably remember how to design a tuned RF rejector circuit once I know the radio frequency of the signal causing this problem.

The other thing that could be done, is to shunt the input junctions of the power amps with a tuned acceptor circuit. However, this would require know how and skills. I doubt you will find anyone willing to do this for you. I did have to do this in my case. It was not difficult as it was a tube amp.

This is another one of my beefs about receivers. The law requires that they have built in rejection of these unwanted signals. The lousy receiver manufacturers widely ignore this, to shave a few cents.

This is especially problematic because of LED light bulbs especially when controlled with SCR dimmers. These make a lot of RF, and you have to really wire your house to minimize it. This is a potent source of RF and causes hums and buzzes often confused with ground loops.

Lastly I have to be honest, that not all these cases can be solved. Some defy resolution, and the only remedy is then to move to a residence much further from the offending tower.
Hey man,
Thanks for the thorough reply! You're speaking way above my level, but I'm sincerely impressed with your knowledge. I actually nailed down which radio station is coming through and I called the owner of the station. He's going to have his engineer reach out to me to try and find a solution. If that doesn't work, I have a question about one of your statements above.

"2 inches or so long and put them in series with the positive speaker leads right at the output from the amp."

Do you mean the ferrite rod should be 2 inches long and to wrap the enameled wire tightly around the rod 5-10 times?

Also, this part confused me: "put them in series with the positive speaker leads." What do you mean by put them in series? I guess I'm just struggling to picture how this works with my original speaker wire.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Hey man,
Thanks for the thorough reply! You're speaking way above my level, but I'm sincerely impressed with your knowledge. I actually nailed down which radio station is coming through and I called the owner of the station. He's going to have his engineer reach out to me to try and find a solution. If that doesn't work, I have a question about one of your statements above.

"2 inches or so long and put them in series with the positive speaker leads right at the output from the amp."

Do you mean the ferrite rod should be 2 inches long and to wrap the enameled wire tightly around the rod 5-10 times?

Also, this part confused me: "put them in series with the positive speaker leads." What do you mean by put them in series? I guess I'm just struggling to picture how this works with my original speaker wire.
You have the construction of the ferrite rod inductors correct. In series means you connect one end of the inductor to the +ve speaker terminal of the receiver and the other end to the +ve speaker cable.

I'm glad you involved the radio station. Make sure they see what I wrote above. Sometimes professional engineers do not understand how this happens.
 
S

siper

Audiophyte
Just an update: the radio station (AM 1490) engineer had my buy a bunch of .1 uF capacitors to place on the receiver posts and the speaker posts. They cut the noise in half, but the radio station noise is still pretty distracting. He now recommends installing these chokes in line:
I've ordered 10 and we'll see how that goes.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Just an update: the radio station (AM 1490) engineer had my buy a bunch of .1 uF capacitors to place on the receiver posts and the speaker posts. They cut the noise in half, but the radio station noise is still pretty distracting. He now recommends installing these chokes in line:
I've ordered 10 and we'll see how that goes.
That bloke slept through his classes. Putting a cap across the speaker terminals was extremely risky. It could have sent your receiver into supersonic oscillation and blown it up.

That choke is also useless. It contains far too much fine gauge wire and will have way to high a DC resistance and will seriously change the Q and tuning of your speakers.

From what you say, I have a strong feeling that AM station is using far too much power and could well be operating illegally. I would make a formal complaint to the FCC about it.

It seems to me a tuned rejector circuit is going to have to be designed for that frequency (1490) and placed in the positive lead of each speaker at the receiver.

I moved recently, and I still think I have an old RF generator, I don't know if it still works. If I find that and this old geezer can still remember his physics, I can get this job done for you. However I start my radiation treatment next week so you will have to be patient.
 
S

siper

Audiophyte
That bloke slept through his classes. Putting a cap across the speaker terminals was extremely risky. It could have sent your receiver into supersonic oscillation and blown it up.

That choke is also useless. It contains far too much fine gauge wire and will have way to high a DC resistance and will seriously change the Q and tuning of your speakers.

From what you say, I have a strong feeling that AM station is using far too much power and could well be operating illegally. I would make a formal complaint to the FCC about it.

It seems to me a tuned rejector circuit is going to have to be designed for that frequency (1490) and placed in the positive lead of each speaker at the receiver.

I moved recently, and I still think I have an old RF generator, I don't know if it still works. If I find that and this old geezer can still remember his physics, I can get this job done for you. However I start my radiation treatment next week so you will have to be patient.
Man, that'd be awesome. Happy to pay you for your time if you can make it happen. I'd normally attempt stuff like this on my own, but I'm just so out of my element from a technical perspective. I'll shoot you a PM.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Man, that'd be awesome. Happy to pay you for your time if you can make it happen. I'd normally attempt stuff like this on my own, but I'm just so out of my element from a technical perspective. I'll shoot you a PM.
OK this what you need.

one of these for each speaker.



One of these for each speaker.



It will come one size or the other, you just need one cap per speaker.

Now you solder a cap and an inductor in parallel. Rap it in insulating tape so you do not get shorts. You solder one end of a combo to each +ve speaker lead, and connect the other end of the combo to each +ve speaker terminal.

If that does not do the trick, then your receiver will need modification to improve its RF rejection.

Mouser are very efficient and easy to deal with.
 
MR.MAGOO

MR.MAGOO

Audioholic General
Sorry if I get off topic, can cell phone towers cause problems like this?
 
TLS Guy

TLS Guy

Audioholic Slumlord
Sorry if I get off topic, can cell phone towers cause problems like this?
Very unlikely. They are digital signals. So you would not hear voices or music. The frequency is very high, this makes this problem very unlikely. I suppose it is just possible that you could get some hash from the odd product.

I will say though that manufacturers are not doing nearly enough to mitigate this RF problem in their products.
 
highfigh

highfigh

Audioholic Overlord
Guys, I'm stumped. I'm getting a spanish radio station blasting through my stereo on every input and in every speaker. There's a radio tower (AM, I think) that's about 500 yards from my house. I think narrowed it down to the speakers or speaker wire, but don't know what to do next.

Gear: Denon receiver, Polk Surrounds & Center, Canton Fronts

Speaker Wire I'm using

Steps I've taken:

  1. Ensure the outlet I'm using is grounded
  2. Tested with headphones. As I'm listening on my headphones, as soon as I start to unplug each speaker, the radio signal gets quieter and disappears when I unplug the last speaker cable.
  3. Ferrite Rings on ever speaker cable and power cable. Didn't have any effect.
  4. Shielding wire for the full length of a speaker cable. Didn't have any effect.
  5. Called Denon. They just told me to reset the receiver and if that didn't work, then I need to send it in for servicing. Reset didn't do anything.
  6. When I turn on the "Eco" function on the receiver, the sound goes away (but that essentially just turns off the surround speakers).
  7. Plugged in the radio receiver that came with the Denon. No effect.
Are there any experts out there that can help me before I throw everything away and buy a soundbar?
You can have grounded outlets and hospital grade parts, but if your home's electrical service's ground wire and stakes aren't making good contact with the soil because they're corroded, the soil is extremely dry, the panel has oxidized connections or if the outlets are back stabbed, you can and will hear radio. It's likely that even a sound bar would have this problem, too. I used to hear this through my stereo when the controls and switches needed cleaning, but I also used to hear it through my guitar amp. I cleaned the controls and the problem stopped- the guitar amp needed me to re-solder some joints because at this point, it's 62 years old and that was only a few years ago.

Bottom line- the grounding doesn't stop at the wall or some fancy-schmancy power "conditioner", although they can filter the line voltage if they're designed for it. Munster Cable had a thing called 'Dr Noise', which was used for selling their crap by showing potential customers how much noise was carried on their power lines. I borrowed one of those and one of their less pricey power strips- without a power strip, I was able to listen to a Milwaukee Brewers baseball game broadcast and with the Munster power strip, I was still hearing the broadcast, loud and clear. With my cheap power strip from Office Depot, it was silent. Don't buy into the hype- the best way to make sure the power line is grounded is to verify the connections and measure resistance between the neutral and ground at the outlets being used- the neutral is separate from the ground until it reaches the breaker panel, where it's connected to the pan. If you have BX wiring, it's likely that the metal cladding isn't as well connected from one end to the other as you would hope.
 
TLS Guy

TLS Guy

Audioholic Slumlord
I have the unit made for the OP and sent him pictures to make sure he can install it. I had a couple of PMs from him but now nothing. I guess I will just ship it to him.

I have made it so that it should be robust. It should cut the radio signal at least 20 db by my measurements, and if he uses good twisted 10 AWG speaker cables, he should be OK I hope. He said he had ordered the Belden cable I suggested. That is probably the best speaker cable around.



 
S

siper

Audiophyte
Hey guys,
Unfortunately, TLS' Guy's solution didn't eliminate the RFI. It certainly reduced it, but I still hear mariachi music in the quiet parts of movies. It's certainly a step in the right direction, but now I'm going to try one of those wireless transmitter/receivers for the rear speakers (the ones picking up the most sound). Hopefully eliminating the long speaker wires will kill most of the reception.
 
Verdinut

Verdinut

Audioholic Ninja
Hey guys,
Unfortunately, TLS' Guy's solution didn't eliminate the RFI. It certainly reduced it, but I still hear mariachi music in the quiet parts of movies. It's certainly a step in the right direction, but now I'm going to try one of those wireless transmitter/receivers for the rear speakers (the ones picking up the most sound). Hopefully eliminating the long speaker wires will kill most of the reception.
You have to move very far from Mexico! :D
 
TLS Guy

TLS Guy

Audioholic Slumlord
Hey guys,
Unfortunately, TLS' Guy's solution didn't eliminate the RFI. It certainly reduced it, but I still hear mariachi music in the quiet parts of movies. It's certainly a step in the right direction, but now I'm going to try one of those wireless transmitter/receivers for the rear speakers (the ones picking up the most sound). Hopefully eliminating the long speaker wires will kill most of the reception.
I was afraid this might happen. My tests showed the device reduced the station by just over 20 db. The problem becomes that if you designed higher order filters then you would have too much resistance in the line.

At least now the nuisance problem is the longer speaker leaders to the surrounds. So it seems the front channels are now listenable.

After thinking about it he would be best trying an amp from the preouts. This quite likely would have better RF rejection from the negative feedback circuit. If it did not work he cold return the amp, and then pursue the radio solution. This is far from an optimal solution for many reasons, especially latency.

This amp would be a good choice and comparable to the cost of his radio solution. The chances of it working are good. It seems to me that his receiver power amps, have well below acceptable standards of RF rejection. This is one more episode that convinces me that receivers are miserable devices.

The OP's issue is well known in power amp design. There are known steps to stop it that would add minimal cost. I suppose a some bean counter wanted to shave about $5 bucks of the price and allow this problem to happen.

If the external power amps solve it and they likely will, he should consider powering all his speakers from external amps, and then he will not have to put up with any receiver power amps.
 
S

siper

Audiophyte
New update: the wireless speaker transmitters fixed the problem! There is some latency, but I'm hoping the AVR's room correction will fix it. I appreciate all the help!
 

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