[PLUG] Buzzing speakers

[Galen Seitz]

On 3/24/20 10:23 PM, Michael Barnes wrote:
> Not really Linux related, but very strange. I have a real nice set of Altec
> Lansing computer speakers hooked up to one of my Linux Mint machines. This
> is a three piece set with two desktop speakers and a large subwoofer on the
> floor.

Model number?

> I've had these speakers for at least ten years and they have always
> worked and sounded good.  I hooked them up to this computer about a month
> ago. After a couple weeks, they started making a very loud low frequency
> beep/buzz every thirty minutes.

Can you tell if the noise is only coming from the subwoofer?

> It is about a one second burst. I turned
> them off with the on/off switch on the volume control, and the beep
> persisted. 

So with the switch in the off position, the noise continues?  I agree, 
that's very odd.  That suggests that the switch is only switching the 
audio input, not the power.

> At exactly :29 and :59. I unplugged the audio input from the
> computer speaker jack and the beep continued.

As suggested earlier, it could be RFI, but given what you've described, 
I'm leaning towards a failing power supply.

> There is no kind of logic
> circuitry in this thing. Just an audio amplifier and related electronics.
> The only way to stop it is to unplug it. When plugged in it is like
> clockwork at exactly :29 and :59, regardless of whether it is connected to
> the computer or not. I hooked up another set of speakers to the computer
> and they do not do this. Sad, because these are a great sounding set of
> speakers.

If the speakers were working, but now, without any changes, they have 
started generating noise, I think a cap in the power supply may be 
failing, allowing power line noise to come through.  It could also be a 
cap in the audio path that is failing, allowing RFI to get into the 
audio.  Please post the model number so we can see how they are wired, 
and where the power comes from.

Please confirm that you haven't introduced anything new to your home 
environment (new appliances, etc.) that might be coincident with the 
noise appearing.

galen
-- 
Galen Seitz
galens at seitzassoc.com