I just hooked up some Harman Kardon SoundstickII speakers to my HP Pavilion a1310n desktop. When I crank up the volume on my speakers they hiss. The hissing gets louder as I turn up the speakers. I checked Harman Kardon's site for an answer (Harman Kardon (http://www.harmankardon.com/faq/showfaq.aspx?Region=USA&Country=US&Language=ENG&lstProduct=SOUNDSTICKSII)). They had this to say:
Question: Why do my speakers make static, crackling, humming or hissing sounds?
Answer: First you need to determine where the problem is. Try connecting your speakers to another audio source such as a portable CD player. If you receive the proper sonic results, this will tell you that the problem is in the computer and/or soundcard setup. In this case there are many things to try. 1. Interference may be causing the distortion. Please check all surrounding electrical objects and place the speakers away from the problem object. 2. Ensure that the speaker input jack is pushed all the way into the appropriate jack. Check all the connections and secure them. 3. The volume on your soundcard may be set too high. Decrease the volume in your volume control panel. Also check the volume and tone controls on the speaker. 4. Sound card or audio source material may cause a problem. *note* the quality of the audio source is also a factor (i.e. bad recording). The compatibility of your CD/DVD rom drive, soundcard and software will contribute to the quality of your sound.

The speakers had no hissing when I plugged it into my portable mp3 player. I've tried grounding my computer case, but that didn't work. I even tried connecting the ground, which is also connected the middle screw on an outlet, to the speaker jack ground. Maybe the reason that none of these things worked is that the speaker electrical plug does not have a ground, whereas the system with the portable mp3 player is electrically isolated.

How can I get the hissing to stop?

Do you have another pair of computer speakers handy? Borrow from a friend? A second PC?

Are you using on-board sound? Or a separate sound card? If it's a separate card, try locating it in another slot away from any other cards, such as the video card.

Try plugging the speaker's power cord into a different outlet from the PC's.

Do you hear hissing at low volumes? The speaker outputs from the sound card may exceed the amplifier specs, so lower the sound card volume as Harmon Kardon's help suggested.

HVAC, thanks for all your help.

I used another pair of speakers with the desktop and they hissed just as loudly. I used a second PC with the SoundstickII's and they did not hiss.

I am using the original sound card. I believe it is onboard. The speakers are plugged into an outlet other than the PC.

I do not hear hissing at low volumes. Concerning turning down the sound card volume, what if I want to listen to my music loud?

I guess I need a better sound card, huh?

A sound card is your best bet.

But... if you want to listen to your music loud, connect the digital audio out (if available.. a sound card will normally have it) to a 7.1 channel AV receiver with all speakers connected of course, and be prepared... :D

In this case, keep your sound card volume low, and use the receivers volume control instead... :)