speaker disturbance

speaker disturbance

Post by Kev Ivri » Mon, 13 Oct 2003 10:23:15


Hey all.

I've got a standard run-of-the-mill 2.1 PC speaker set. They work fine with
my laptop except for the following issue. When I have my laptop power supply
plugged in in the same room it creates a buzzing noise on the speakers. It's
especially noticeable if the speakers and laptop are plugged in at the same
outlet (through a surge protector). When I unplug the laptop and play on
battery the music is crystal clear.

How do I get around the disturbance?
Running an extension cable from another room is not an option...=)

Cheers,
- Kev
 
 
 

speaker disturbance

Post by CJT » Mon, 13 Oct 2003 10:55:45


That sounds to me like a classic ground loop problem.

An isolation transformer on either the laptop or the speaker power
supply should work, although it'll cost you a few bucks. You might
also be able to break the loop with some sort of isolator (e.g. a
transformer) on the audio cable, but you might have trouble finding
a suitable yet cheap one.

If you Google "ground loop" you will find myriad discussion.

I am a little surprised to hear of a laptop and speaker system behaving
that way -- I thought their power supplies generally were already
isolated. It's possible one or the other is defective. Or maybe my
diagnosis is just wrong.

Often a cable TV connection is the culprit, but you don't mention one.

--
After being targeted with gigabytes of trash by the
"SWEN" worm, I have concluded we must conceal our
e-mail address. Our true address is the mirror image
of what you see before the "@" symbol. It's a shame
such steps are necessary.

Charlie

 
 
 

speaker disturbance

Post by Kev Ivri » Mon, 13 Oct 2003 21:14:21

Hey Charlie,

Thanks for the reply.

I've read up some of the websites I found on google, and it does sound like
ground loop is a very likely culprit. The thing that has me confused,
though, is that the I read ground loop occurs most often, like you said,
with a cable TV connection - because the cable provider is grounded at a
different location and that it's the resultant differing electrical
potentials that create the hum. But, my laptop and speakers are connected to
the same system.

And even more confusing - my laptop does not actually have a 'ground' plug.
It's one of the standard two-prong plugs. It's not grounded...!

Any ideas?

Thanks,
- kevin






with
supply
It's
same
That sounds to me like a classic ground loop problem.

An isolation transformer on either the laptop or the speaker power
supply should work, although it'll cost you a few bucks. You might
also be able to break the loop with some sort of isolator (e.g. a
transformer) on the audio cable, but you might have trouble finding
a suitable yet cheap one.

If you Google "ground loop" you will find myriad discussion.

I am a little surprised to hear of a laptop and speaker system behaving
that way -- I thought their power supplies generally were already
isolated. It's possible one or the other is defective. Or maybe my
diagnosis is just wrong.

Often a cable TV connection is the culprit, but you don't mention one.

Charlie
 
 
 

speaker disturbance

Post by CJT » Tue, 14 Oct 2003 11:44:41

ev Ivris wrote:

It's possible the filtering on your laptop's power supply is inadequate.
However, I would expect that to result in some difficulties operating
the computer, as well.

Are both 12VAC plugs (on the speaker system and the laptop power supply)
the polarized type (one blade bigger than the other)? If not, does it
make any difference if you reverse the direction they're inserted in the
wall?



--
After being targeted with gigabytes of trash by the
"SWEN" worm, I have concluded we must conceal our
e-mail address. Our true address is the mirror image
of what you see before the "@" symbol. It's a shame
such steps are necessary.

Charlie

 
 
 

speaker disturbance

Post by Kev Ivri » Wed, 15 Oct 2003 07:34:06


Hehe. Well. It's funny you should ask about my plugs.

See, I'm a US resident, currently in the UK. The adaptor for the speakers is
a standard UK plug (which makes it impossible to reverse polarity) at 13.5v.
The adaptor for the laptop is a standard US two-prong unpolarized plug at
15v, connected to the UK supply through a travel adaptor. I tried reversing
the direction of the laptop plug - and it doesn't seem to make a difference.
My guess is the adaptor does the polarizing internally?

Interestingly though, when I reach for the volume/bass/treble control of the
speaker system the buzzing increases as my hand gets closer.

Thanks for all your help...

- kev




It's possible the filtering on your laptop's power supply is inadequate.
However, I would expect that to result in some difficulties operating
the computer, as well.

Are both 12VAC plugs (on the speaker system and the laptop power supply)
the polarized type (one blade bigger than the other)? If not, does it
make any difference if you reverse the direction they're inserted in the
wall?