I have a computer set up at home with a number of monitors, computers, accessories etc. Unlike essentially an identical set up at the office I will at times have static/hum/feedback into the Bose sound system. Rifling the wires around (even though nothing else moves them) will usually resolve it. After many years of this it finally dawned on me to consider some of the RFI shielding cable meshes/sleeves and if putting them around some or all of the cables might be effective in resolving this. Does anyone have experience to provide "feedback" on this?

Many thanks to the wise forum for all that the community does.

You have [noise] induction. Shielding the signal wires and sometimes power wire will prevent the induction.

Poor man's method: wrap signal wires with aluminum foil from source to destination.

Proper method: buy a new set of shielded cables which are/can be grounded at each termination (connection points)

Yes. cable shielding is often effective in reducing crosstalk. Unfortunately, without knowing exactly where the noise is entering the signal path, it can be a trial and error procedure to resolve. Note that the shield may have to be grounded to be effective. Better to use actual shielded cables, if available, than an add-on wrapper. Keeping various cables separated can be enough, it is running them side-by-side in parallel that exacerbates the problem.

Thanks! You've confirmed pretty much what I was thinking. The challenge is in the logarithmic increase in combinations of each cable with the others because there are so many of them. It's annoying because they won't do any of this for weeks then have a moment when they go bonkers, even though all of them are consistently powered the whole time I'm working there. Grounding would be a problem in this old house, so I'll try to identify which wire is the problem. Some of the cables already are shielded, so that cuts down on the combinations to consider.

The shield isn't grounded to the house, per se. Shield is grounded at each end (sounds like in your case (no pun intended), at the computer case and at the speaker(s)).

Typically grounding is accomplished through the connector(s). In rare cases (again, no pun intended), a separate wire is located at each end.

Or you could snap on a ferrite choke on the power supply line going to your speakers closer to your speakers. Just a stab in the dark.

quote:

Originally posted by Rey HRH:
Or you could snap on a ferrite choke on the power supply line going to your speakers closer to your speakers. Just a stab in the dark.

Interesting! Had not heard of that. Will explore and hope to report back.

quote:

Originally posted by ChuckFinley:

quote:

Originally posted by Rey HRH:
Or you could snap on a ferrite choke on the power supply line going to your speakers closer to your speakers. Just a stab in the dark.

Interesting! Had not heard of that. Will explore and hope to report back.

Yes. We hams have to do this sort of stuff to electronic equipment at times and our radios to keep all that common mode noise out of the radio.

Those cables you have a perfect antenna and will pick stuff up and pass it along to be rectified in your Bose speakers (depends how well they are made - they 'should' block the RF signal being picked up via your inadvertent random wire antenna).

You'll note Toroids on computer power cables for instance or good quality usb cables for audio connections. Wires are antenna and there is a shit load of Radio Frequency noise out there.

quote:

Originally posted by LS1 GTO:
The shield isn't grounded to the house, per se. Shield is grounded at each end (sounds like in your case (no pun intended), at the computer case and at the speaker(s)).

Typically grounding is accomplished through the connector(s). In rare cases (again, no pun intended), a separate wire is located at each end.

Technically speaking, and there is a lot of differing information out in the ether regarding this, grounding both ends reduces the noise reduction.

I normally only ground the source end. There have been numerous times I've reduced noise problems by breaking the termination end shield...

Regardless, in this application I would try the ferrite choke first, if it's RFI vs induced noise, the choke will work better...

As a musician who uses electric pickups… Very sensitive to EMI.


A lot of EMI can come from other sources than your cables; especially computers.

Windowed computer cases and monitors are a huge source of EMI. Downright terrible.

Might also be a grounding issue assuming the Bose speakers are plugged into the Computer in some fashion. I.e. if the speakers are plugged into a different electrical socket that's on a different ground/electrical path than the electrical socket the computer is hooked to. I had humming issues with powered Speaker monitors attached to the PC, that I fixed with an inline $10 ground loop noise isolator from Amazon.

Power supply bricks can generate noise. Some hams will find through elimination a power supply offending, and seek mitigation for only that issue.

quote:

Originally posted by ChuckFinley:
Rifling the wires around (even though nothing else moves them) will usually resolve it.

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What do you mean by rifling them around???. Do you mean moving them away from something, or moving them such that a bad (resistive) connection suddenly reseats and fixes the issue, at least for a while?

is this repeatable?. can you start at position A and get the noise, and then to B, noise goes away, then noise comes back at position A?

What is the audio interface? cheap analog 3.5mm audio cable, or is it another type of interface?

How are the speakers powered? Some wall wart, standard AC cable? with or without ground?

Can you bring components from your noise-free office and substitute in at home to see if these components suffer the same noise? Can you bring the speakers with the Noise issue to work to try?

I ask these questions, but this type of troubleshooting can be very difficult without actually being there. But we do the best we can.

quote:

What do you mean by rifling them around???.

I suspect he means interweaving them in a braid or twist pattern. This is what gives twisted pair cables relatively greater noise immunity than UTP. For example, in Ethernet cables, as the Cat number increases, so does the twists per foot of the signal pairs inside the sheath. The variation in coupled signal phases serve to provide cancellation of the hetrodyned noise frequencies. These twists are intended to reduce radio frequency noise, whether they are as effective in reducing noise in the audio frequency range may be debatable. Also up for debate might be the usefulness of this technique on amplitude modulation as opposed to differential signaling. But what do I know? I'm a digital guy, this analog stuff gives me headaches!

What the heck, braid your cables all you want, just don't assume that it is going to make a difference.

quote:

Originally posted by architect:
.....twisted pair cables.....

{snip}

...... These twists are intended to reduce radio frequency noise, whether they are as effective in reducing noise in the audio frequency range may be debatable.

It worked well on the old fashioned landline phones that most of us had while growing up. These were audio freq range, and used twisted pairs.

Iirc, AC power lines should optimally be away from audio cable. Never run parallel for inductive reasons. Cross at 90° if necessary.

There a tons of things that generate noise in the house, like dimmer switches for a starter. Or it can be a transformer outside your house, or something your neighbor is doing. Ymmv

Finally identified that it was the audio cable from the computer to the Bose system. Moving it, and shielding it seems to have done the trick.

quote:

Originally posted by ChuckFinley:
Finally identified that it was the audio cable from the computer to the Bose system. Moving it, and shielding it seems to have done the trick.

Very common.
Another solution could be a USB 'sound card' that moves the analog connection away from the computer case & usually the USB 5v line is less noisy than the motherboard analog outlet.
It can simplify wire management as well.

Thanks. I will keep that in mind, should the sound problems return