buzzing in surround sound

[dmartn149]

I've been getting intermittent buzzing sounds from my surround sound system. It's a bzzzzzzz bz bz bz bz. I've put Radio Shack ferrite snap cores over most of the cables and all the speaker wires. That seemed to quiet it down, but it is still there.
Any ideas on what to do next?
Thanks

[Enzo]

Sure. FIND the source. I have a cordless phone next to me. Just sitting there it makes a buz-buz-buz constantly into nearby amps. If I pick up the handset and turn that on, then the noise increases. Turn off anything computer. ANy change? I used to have a CD player that made a whiny noise into my amps from across the room. I could see its blinking display exactly matched the noise pattern. Turn off the overhead lights.

TURN OFF the cell phone. I know that is against the will of God, but a few seconds to determine it if is involved won;t kill you. If you JUST can;t make yourself do that, at least take it 20 feet away.

Get out a portable AM radio, tune it to between stations and turn it up. Now aim it all directions, use it like a radar. Does it pick up any noise patterns same as your buzz?

Does it mainly happen at certain times of day? Like commuting times when all the area garage door openers are running?

Got home security system? Turn that off and see.

And my favorite experience: I had an amp that every 45 seconds or so, it made a buzzing noise. Turned out that the trafffic signal at the end of the street gad a noisy triac, and every time a certain one of the lights was on, it sent an electrical noise all over the local power line.

[dmartn149]

Wow, I didn't realize there were so many potential sources of interference. We have a cordless phone with 3 hand sets, 2 cell phones and 2 laptops that are usually on. I guess I'll have to try turning things off one by one. I don't mind turning off the cell phones. No one calls me anyway.
Thanks Enzo

[soundguruman]

Ground loops.
Cable TV will cause quite a buzz, use a cable TV isolation transformer.
Amazon.com: Viewsonics VSIS-EU Cable TV Ground Loop Isolator: Electronics
Sub Woofer- lift the power ground with a plug adapter.
TV- also the ground on the TV can be lifted.
Power | Converter | 3 Prong | 2 Prong

Using these 2 devices, almost any surround system buzz will be eliminated.
(licensed sound system contractor / installer, experience 35 years)

[dmartn149]

Ground loops.
Cable TV will cause quite a buzz, use a cable TV isolation transformer.
Amazon.com: Viewsonics VSIS-EU Cable TV Ground Loop Isolator: Electronics
Sub Woofer- lift the power ground with a plug adapter.
TV- also the ground on the TV can be lifted.
Power | Converter | 3 Prong | 2 Prong

Using these 2 devices, almost any surround system buzz will be eliminated.
(licensed sound system contractor / installer, experience 35 years)

Do these techniques apply to RF interferance? It is not a constant hum like I would expect from a ground issue. When it happens it only lasts about three seconds. Usually it is one long buzz followed by three short. Sometimes it happens many times a day, other times it is only a couple of times.

[Jazz P Bass]

Did the system always do this buzzing.

If not, you may have a problem with the unit itself.

[soundguruman]

Do these techniques apply to RF interferance? It is not a constant hum like I would expect from a ground issue. When it happens it only lasts about three seconds. Usually it is one long buzz followed by three short. Sometimes it happens many times a day, other times it is only a couple of times.

No does not apply to RF interference.
Cable TV uses AC power on the trunk line to power the cable trunk amplifiers, about 77 volts or so.
What happens is this AC is on the cable ground. So when the TV or Subwoofer is grounded to the power ground, the Cable ground causes a ground loop.

Disconnect cable TV entirely from the system and see if the buzz stops. (including FM connection from cable)

In that case use the isolation transformer to block the cable ground from connecting to your system.
In many cases that does work. It's a really common problem with home theater systems.

Look very closely at the TV picture, when you are watching cable TV.
Is there a faint horizontal line, (almost a ghost image) floating up or down in the TV picture?
That's a sign that there is a cable TV ground loop.
You will not only hear a buzz, you will also see that faint line moving up or down in the TV picture.


Another common one is the Subwoofer ground or TV ground causes a ground loop.
Lift the ground using the AC plug adapter, to the sub or TV or both. See if that stops it.

It's usually one of those 2 that will stop the noise.

[dmartn149]

Did the system always do this buzzing.

If not, you may have a problem with the unit itself.

Yes it has always done this, though I only recently set it up so that it comes on whenever the TV is on. I used to just turn on the surround for certain programs. It did it then too, but being an intermittent issue on a device that I didn't use all the time, it didn't bother me as much. I hear the same sound on my wireless phone sometimes too. I'm not sure if the surround does it at the same time as the phone, but I wouldn't be surprised.

[Jazz P Bass]

Start turning items off.

Cell phones are notorious for 'calling home'.

[dmartn149]

Well, I've had it on all day while doing stuff around the house, and it hasn't done it at all. All the usual electronics have been on too.

[dmartn149]

I just installed a new v-tech phone system last night. Now I'm thinking the old system might have been the problem. Sorry if I've wasted your time. I only replaced the old phones because the batteries wouldn't hold a charge any more. I never thought they might be the source of my surround noise.

[g1]

Today was also a holiday. It could be some kind of business related interference (like a welding operation or something).
The fact that you also heard it through your phone means it was some kind of external interference. Try to keep track of what times of day it happens or if it is a 24/7 issue.

[dmartn149]

Yes I thought about it being a holiday, but I kind of live out in the country. I don't know how close a source of interference has to be, but I only have two close neighbors. We are each on 1 acre lots, so we are not real close. There are no businesses near by.

[Mark Hammer]

Many, though not all, surround systems, particularly older ones that employ through-hole parts, rather than surface mount LSI chips, will employ bucket-brigade devices to achieve a short delay between "front" and "rear". These are easily identified by the MN3xxx part numbers if they use Panasonic chips, or RD5xxx if they use Reticon chips. BBDs require a high-frequency clock to move the signal from input to output, but "high frequency" depends on what you consider high. If using a 1024-stage MN3207 to produce the requisite delay, the HF clock may be running at 10-12khz, which is low enough to produce an annoying buzz.

Take a peek inside and see if you can spot a BBD anywhere in there.

[dmartn149]

Thanks Mark, but it looks like it was the phone. It's one of those wireless land lines with 3 hand sets. No buzzing now with the new phones.