[nreel]

Try opening the Audio Controls and check the slider on the WAVE/Mp3.

Make sure the WAVE slider is above 50%...set it at 100% if you like.

No, the Power supply in a computer doesn't have anything to do with the amount of Power out of the Sound Card.

Usually, Powered Mixers do not have XLR LINE Inputs.

It appears that your Powered Mixer "Yamaha EM88s 250-400" is rated at 250Watts Stereo (250W per Channel) and 400Watts Mono. For Yamaha, this, usually, means at 8-Ohms.

Your Yamaha Series s115 club series speakers, if they are actually CLUBIV or CLUBV speakers, are rated at 500Watts Program and 1000Watts Maximum at 8-Ohms. In stereo mode (250W per Channel) you would be grossly under powering these Speakers. Even with your MASTER Volume at MAX, you would need to have the Volume, on the LINE IN Channel, up 100%, if you had any crowd at all. If you had 100 people or more, you would never be able to get over the loudness of the crowd!

I know what you were thinking when you put this system together...that, no way will I be able to Blow these speakers, but the opposite is the case. With your AMP at MAX...all the time...you are more prone to clipping (bad frequencies going to the Speakers) and, therefore, a higher probability of blowing the Speakers. Not to mention the fact that your AMP has NO HEAD ROOM and, if run continuously like this, will fail.

You should look into running your AMP in MONO. This way you get 400Watts, which is closer to the Program Rating of your Speakers and give you more HEAD ROOM on your AMP.

Or, buy two more CLUBV (CLUB IVs are obsolete) and Parallel them. The resistance is halved in Parallel. 2 8-Ohm Speakers, in Parallel, become effectively 4-Ohm Speakers. Therefore, 4 8-Ohm Speakers hooked in Stereo, should give you the 400Watts per Channel and more HEAD ROOM on your AMP.

As far as HUM goes, you can by a HUM eliminator, as GDUNS suggested, or lift the Ground, which is not as safe, as others have suggested.

It may be one of your MICs causing the HUM. You didn't give any info on your MICs as to whether they were connected to the Mixer via 1/4" or XLR.

Unplug each MIC, one at a time, and see if that clears up the HUM.

Norm