1 channel not clear

This could be caused from a whole array of things.

Assuming your input signal to the amp is clean, and your installation is good, my first guess would be a bad output transistor. Most car amplifiers are Class A/B, which in a nutshell means they use two transistors for each output channel (or more in a bigger amp, but always a multiple of two). The transistors take turns with the load. When one is on, the other is off, and they hand off the signal. If one is bad, or partially bad, the other may still be working which will generate a signal out of the amp, but it will be heavily distorted. Sometimes depending on how the transistor is dead, the output will sound like audio mixed with static.

This is just one guess at many possible issues your amp may have.
 
This is the amplifier in question, in case anyone has any ideas what to do about it. My suggestion is to get a better amp which is a discrete design, but budget constraints may not allow for that.

junk_amp.jpg
 
That amp doesn't use a step up power supply, so it can't have more power than a regular head unit. definitly *NOT* 600 (PMPO) "watts".

I'm nt sure if the problem wold lie in the preamp (the big bunch of resistors and capacitors in the middle of the amp, the few discrete transistors there are, and the pots, opr in the big chip screwed to a heatsink (the power amp). You could test by breaking the connection between the pre amp power amps and swapping the left and right channels, and see if the noise is in the other channel after you did that (cut circuit board traces, and solder some jumperwires). But I would not consider this amplifier to be worth the trouble to repair. bummer.