Originally Posted by: Thinhho 
just want to verify if you have same issue as discussed ealier, the compressor took care it. then i may buy one.
Chào Thinhho,
Sorry for the delay response.
Let discuss about noise in the sound system.
As u or I known that we used the home stereo system and we don't have that problem.
Y home stereo doesn't has that problem? Because home stereo only has one control volume.
We gathering all the gears and cables to make karaoke system.
Different manufacture for each gear.
Some manufacture make good gear because they include noise reduction in the gear and some manufacture don't.
So we rig up a karaoke system, now the system is not only have one control volume but it has multiple control volumes in the system such as pre mic volume, mixer volume, xf volume, EQ volume, compressor volume, and amplifier volume.
If we turn all the gear control volumes down or completely zero then it fixed the noise but the output would be not enough sound or not at all.
Since the system has too many volumes control, we turn some of those gear control volumes up 50% to 100% and We control at the mixer control volumes.
Anytime we have one gear control volume turn up, let say the amplifier volume is set 80-100% most of the time.
That amplifier will pick any signal is come in from the input, because we has assigned that amplifier to be active, be ready to pick up signal and output out at high volume of watts to the speakers.
Let be more clearly by give an example: a water facet at the house. if u open a little, water run it has less noise. If u open full, water run has more noise.
Same theory applied to the amplifier.
That y we have to learn to control it.
Found where the problem is come from and fix it.
Try to use the power outlet strip with surge protector, don't use cheap power outlet strip.
Sometime the wall plug outlet has bad ground(that was happened to me at my house)
I use compressor on the mic channel strip, plug in at the insert plug to control voice.
I used another compressor hook up between the mixer and power amplifier for two purposes to control the main sound and noise.
The 2 purposes are:
One, control music sound from peak out causing distortion, contour, threshold, sound ratio, sound attack, sound release.
Two, using the threshold expander/gate to control noise when pause the music or nothing going on while system is active.
If u want to understand more, go download either dbx 166xl or dbx 166xs manual and read on the threshold expander/gate.
U can buy use dbx 166xl for $89.00 or cheaper on Guitar Center online. The dbx166xl is discontinue model. New dbx 166xs is $239.00
