Buzzing sound from speakers

[fsiiopu]

My PC is connected to a home theatre system via an amplifier. The home theatre system's plug is two pronged and all the plugs including those of PC and monitor are connected to the same extension cord that is connected to the wall power outlet by a three pronged plug. When I plug the 3.5mm cable from the amplifier (home theatre) to the sound card output I hear a loud buzzing sound. Please help.

 

[GokAy]

Until someone else comments - can you test the 3.5mm cable with something else? Like your phone?

 

[fsiiopu]

Until someone else comments - can you test the 3.5mm cable with something else? Like your phone?

Very little when plugged into the laptop with battery power

 

[GokAy]

Do you have another 3.5mm cable? You have to try another cable on your system and also try that cable on some other system to eliminate possibilities.

 

[fsiiopu]

Do you have another 3.5mm cable? You have to try another cable on your system and also try that cable on some other system to eliminate possibilities.

Same outcome mate

 

[fireberd]

Sounds like a "ground loop" hum. Usually, lifting the AC power ground on one piece of equipment will correct this. With a two prong AC power cord, reversing the cord will sometimes fix it.

I used to be a guitar amp tech and ground loop hums are a common problem in musical equipment.

In reference to the cable, it should be a shielded audio cable, not a "speaker" or speaker extension cable as they normally are not shielded.

 

[fsiiopu]

Sounds like a "ground loop" hum. Usually, lifting the AC power ground on one piece of equipment will correct this. With a two prong AC power cord, reversing the cord will sometimes fix it.

I used to be a guitar amp tech and ground loop hums are a common problem in musical equipment.

In reference to the cable, it should be a shielded audio cable, not a "speaker" or speaker extension cable as they normally are not shielded.

What is "reversing the cable"? Please explain.

 

[fireberd]

Reversing the cable? On an AC power cord with a two prong plug, reverse how it is plugged in to the AC receptacle. If its not a "polarized" plug (one lug is wider than the other) its easy to reverse. If it is a polarized plug and adapter is needed.