Have a xga 4000 amp only channel 2 works fine . Channel 1 very very low

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Not much on it, but make sure vents are clear

https://www.google.com/search?q=xga+4000+protect+mode+reset

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I have a Gemini xga 4000 that only channel 2 works fine but channel 1 is very very low .......

I have same problem. i have this map. please help me to find the problem. if you can point the area in this map that problem is from that.

Bass cancellation can occur if the polarity of one cable is reversed? Positive at the amp MUST go to the positive at the speakerS else one speaker will be pushing & the other pulling & the low frequencies get cancelled. You may also hear some strange imaging effects as you walk around the room - a bit like stereo from a mono setup.... check your cables :-)

MAKE SURE the cables you plug into 1/4 inch mains are TRS plugs, and not mono cables (TS). The main output 1/4 inch jacks are TRS balanced outputs and if you plug mono (TS) cables that shorts out the ring connector reducing the power by 6 Db. USE ONLY TRS balanced cables for interconnects !!!! Also read my tip on Fixya regarding PMP mixers. If you use 1/4 inch SPEAKER cables or adapters, if you short the SLEEVE of channel A output to ground you can pop the channel A amp. The TIP of channel B is the hot BUT the SLEEVE of channel A is the HOT. The ttip I posted explains why this is and it isn't mention in the Behringer documentation.

The user manual is located at: http://www.bugera-amps.com/PDF/Downloads/1960_P0671_M_EN.pdf on page 5; When the HIGH 1 and LOW 1 (or HIGH 2 and LOW 2) connectors are used simultaneously, their sensitivity is the same (both LOW). This may be your problem however--- Try swapping input chanels to see if the problem follows ther cable or is in the amp.
Assuming it was working before, you may have a short in the cable or a bad component or tube in the amp. Tubes can be difficult to come by. If the other channel works correctly, It may be one of the small tubes. Hope this helps

Wayne, There's a time to take the amp to a pro shop andf get it done right. It' saves time and headaches, and also keeps you from inadvertantly smoking other parts or yourself. Now is that time.

It sounds like a job for a technician. There are high voltages in the chasis and the potential for a serious shock to the unwary. 

That said, I can suggest several possibilities.

First, make sure the controls aren't causing the problem. Contacts can build up dirt and oxides and block the signal. Try twiddling the controls and see if the problem comes and goes, or if you hear scratchy noises. If symptoms are found, buy a contact cleaner spray, take out the chasis after unplugging and letting it set for an hour, being very careful not to touch any exposed conductors inside. You'll see some holes in the control bodies; squirt cleaner for 2-5 seconds and work the controls.
Also see if the problem happens without the footswitch, and try the channel switches several times - same problem, dirt and oxidation.

Other possibilities - cathode bypass capacitors drying up, and it looks like the amp uses some opto-couplers at various stages. 

The slider or the amps for channel 1 may have a problem.

Sliders do wear out.

Try shorting channel 1 input and see if that affects the noise. A hissing noise is probably a bad preamp chip. That is shop work at a repair facility.

Replace the switch. You gave no make/model number for your amp but if it has a jack for foot pedal operation of clean/dist function then try that. (on most amps) it will switch in spite of a bad front panel switch.