How can I get rid of hum from speakers

Question

Level 1

4 points

How can I get rid of hum from speakers

Hi,
The computer : MacBook Pro 2.4 GHz + Leopard 10.5.1
The speakers : Altec Lansing VS4121
The problem : when I connect the speakers to the cumputer, a hum comes from the subwoofer ; when I disconnect, no more hum.
The tests :
1) I moved the power cord from the power surge protector and I connected it directly into an AC wall outlet : always hum
2) I moved the cables and checked to see that they were making a good connection ; always hum
3) I checked in the Preferences : everything is set alright

Do you know how I can get rid of that disturbing hum ?

Best regards.

Piergis

MacBook Pro 2.4 GHz, Mac OS X (10.5.1)

Posted on Dec 22, 2007 8:22 AM

Reply

Answer 1

sgginc

Level 3

676 points

Dec 22, 2007 10:22 AM in response to Piergis

COULD be ground loop feedback ..

See this:
http://www.amazon.com/Xitel-GLI1-X1-Ground-Loop-Isolator/dp/B00023XDYA/ref=pdbbs_sr1?ie=UTF8&s=electronics&qid=1198347534&sr=8-1

Read reviews to see if it matches your issue:
http://www.amazon.com/review/product/B00023XDYA/ref=dptop_cm_cr_acrtxt?%5Fencoding=UTF8&showViewpoints=1

ken

Reply

Answer 2

Piergis Author

Level 1

4 points

Dec 22, 2007 2:12 PM in response to sgginc

Very interesting ... but the device doesn't seem suitable for the kind of cable (3.5MM (1/8") PLUG TO 3.5MM (1/8") PLUG) joining together the speakers and the computer.

Thanks.

Piergis

Reply

Answer 3

sgginc

Level 3

676 points

Dec 22, 2007 5:54 PM in response to Piergis

If it sounds like your issue you can get an adapter.

Also there are cheaper devices from about $10.

ken

Reply

Answer 4

MalcW

Level 1

35 points

Dec 23, 2007 2:08 AM in response to Piergis

Interesting comment - I have used a G5 iMac upgraded to Leopard and I have bought the Harmon Kardon Soundsticks. Interestingly the hum comes on immediately you put the computer to sleep. Clearly it sounds like a ground loop but it isn't obvious how you fix it - apart from switching the Soundsticks off! Must try it with my MBPro

Reply

Answer 5

sgginc

Level 3

676 points

Dec 23, 2007 5:47 AM in response to MalcW

IF it's a ground loop it is eliminated with a ground loop isolator ... See above links.

ken

Reply

Answer 6

MalcW

Level 1

35 points

Dec 24, 2007 9:03 AM in response to sgginc

Thanks - actually it's not such a great problem but like Piergis I'll need to source a 3.5mm adapter because the Speakers simply plug into the headphone output port of the G5. I'll do a search. Thanks again for the tip.

MalcW

Reply

Answer 7

Mengoxon

Level 1

0 points

Jan 10, 2008 10:55 PM in response to MalcW

I have the exact same problem with Audioengine A2s - hum comes on after sleep immediately or a while after sleep. I actually tried resolving the problem with a ground loop isolator (called GL-205) and it certainly did not work - in fact that thing made my speakers hum all the time 😟 (different sound, though)..
The thing about the ground loop theory: Both the MacBook and the speakers are actually not grounded or are they?
Both use C7 line sockets (shotgun or figure of eight) which are not grounded. Or is the MacBook grounded through that connection bit in the power plug? Can somebody with electrical knowledge please clarify?

Another thing, I tested the speakers with my Mac mini and unfortunately it had the same problem 😟

Reply

Answer 8

Jan 21, 2008 10:46 AM in response to Piergis

I have the same problem too, the "hum" sound kind of loud. Specially when my PowerBook Pro (2.2GHz) is not plugged into the power line and working with the battery only.

I have Altec Lansing Speakers which I love. My brother told me about the ground thing, but a friend of mine who bought the 2.4GHz came to my house, plugged his computer into the same powerbar as me, plugged my speakers into his computer and it doesn't make the hum sound.

Would that mean that my computer has a electrical problem?

Reply