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how to minimize speaker hum

G

GunsMadeAmericaFree

Golden Member
For about the last 20 years, whenever I built a PC, I would install an inexpensive PC stereo speaker into a 5.25" drive bay. The speaker had a headphone wire/jack that went back through the chassis, out through the back, and plugged into the headphone out jack on the back of the PC. My wife and I love the fact that you can quickly reach up and turn a physical knob to turn volume up and down whenever needed.

A couple of years back, I noticed that there started to be a hum in the speakers on one of our 3 PC's. I assumed it was the speaker itself, and old "Thor" model that was probably 15 years old, and I ordered several replacements.
Strangely enough, the interference persisted even after:

1) completely replacing the speaker and wires, and then doing it again

2) replacing the power supply

3) We also had to replace the motherboard, and doing that didn't seem to make any difference, either. (we're using the motherboard's built in sound chip)

I'm not sure what else my options might be to isolate the generated signal hum. Since I replaced the power supply, and I replaced the actual speakers twice, I'm thinking it was not either of those. I don't need anything fancy, just stereo sound. I'm wondering if there is anything else easy I can try that might give some light on why this is happening?

We don't need anything fancy, we just want very basic sound that we can turn volume up and down easily with the built in analog potentiometer wheel for volume.

Any thoughts on where we could start? It's a very small problem, but it ANNOYS me...
 
Ken g6 said:
This is one reason I use a Bluetooth speaker.
Click to expand...
I really like to stay away from wireless, since there can be dropouts, interference, etc. However, I wonder if I could somehow try some sort of USB sound solution, and run the audio out from that to the back of the speakers.... hmm.
 
I just scanned post #1 and briefly the comments.

Isn't this a problem of speaker power or device power not being isolated from AC power? That's why I use UPS systems. And since some speaker systems have an AC power plug, I would isolate those as well.
 
IMO, basic analog audio setups started getting noisier and noisier with each newer generation of PC hardware that had higher power state changes, due to ground noise, made worse if you have a halfway decent video card in the system.

Easiest solution is external DAC, or USB audio box/dongle/etc. Sometimes a PCI/PCIe sound card can solve it, other times not.

Without changing anything else, it can sometimes help to turn the PC's volume mixer up, and the speaker volume pot down. That doesn't get rid of the noise, just reduces it's volume.

Then there's the long-shots... once upon a time ago, I had a land-line, cordless phone handset a foot away from a standalone PC speaker amp that was in an unshielded box. Every few minutes, without even using the handset, it would communicate with the base station located dozens of feet away and cause humming in the speakers for those events.
 
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sdifox said:
You can buy shielded RCA cable. Most MB have audio header no? That probably routes better than going out the case to the plugs.
Click to expand...
You'd think so but ironically not too long ago I made a custom slot bracket with isolated RCA jacks put on it, going to a motherboard header 3" away and it introduced hum that wasn't there before.

The original goal wasn't to get rim of hum but that the rear panel 3.5mm line out was getting intermittent contacts. In the process of swapping out the 3.5mm to RCA (to monitor speaker (freestanding speakers with built-in amp not in a visual display type of monitor) cable to go RCA to RCA, I had a box of cables to choose from and when it got the hum I switched it back but can't recall if I used the same original cable or a different 3.5mm to RCA instead. Either way switching back to the 3.5mm rear panel out worked again.
 
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GunsMadeAmericaFree said:
Hmm. I wonder if they make something like duct tape that you can wrap around wires, but blocks RF interference?
Click to expand...
It wouldn't surprise me if they came up with something but generally the wrap needs to be connected to ground on one end which means a crimp, or a solderable metal material. Sometimes it is enough to just tightly twist the wires together, something about that making no single sided length as long as the wavelength being picked up. Back in the day you'd often see cheap analog cables from optical drives made like that, or you could try replacing the cable with shielded wire (if it isn't already?).

The question is what changed since you originally installed the speaker module? Presumably they didn't have the hum when first installed in same system? If that's true you might look at whether the volume pot is intermittent and could be cleaned out or whether there's any capacitors on it's amp board that are failing.
 
GunsMadeAmericaFree said:
Hmm, would aluminum foil work? I just ordered a USB audio dongle, and am going to connect those front speakers to that, and see if there is less noise.
Click to expand...

it would, but since it is conductive, you might want to wrap something non conductive over the aluminium. Your cable would be pretty stiff at that point. You can ground the shielding to the computer case.

I don't understand installing speakers in PC, but you do you.
 
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This is one of those situations where you start out with a little problem and before you know it you've spent £600 and just realised that every improvement shows you another problem to solve!
Its like trying to silence your PC! (That said that's a lot easier now that HDDs are unnecessary, I can now no longer tell if my PC is on if the monitor is off!)


Humming from speakers is normally a ground loop thing but if you have the speaker wire going through the case you probably have some interference going on as well.
 
How are you actually getting stereo sound from two speakers in a 5.25 bay? Surely they are too close together to give any stereo separation?

If they were on the (physical, as in desk) desktop you'd still be able to use the knob but you'd cut down on interference as the cable wouldn't be going through the case, you'd get decent stereo, and you could get larger speakers if you needed to.
 
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