Zoom LiveTrak L-20

I bought the zoom a couple of years ago, and at the time I thought that it was working fine, but recently I discovered that there is hiss on my speakers (and also on my headphones), just by putting one fader up (if I put multiple faders up the noise gets very loud), which is NOT normal. I wanted to record my voice and other instruments, but this is simply not possible now. Perhaps it was like this from the day of purchase, I just did not notice it until recently. I thought it was my speakers' fault.