When connect sub wire to I just get a humm noise and it goes into protect mode what cause that

Bad or shorted voice coil on sub maybe. If you have two subs try them one at a time to see if it goes into protect mode. Whatever sub does it is bad.

Disconnect all speaker connections and rca cables. Leave power, ground and remote wires intact. Try turning on again. If you still have a protection light your amp is faulty. Hopefully you have warranty . .A thumbs up would be greatly appreciated if this answer is helpful to you

First disconnect the CD head unit from the sub amp and see if the other amp works. If yes, the problem is the wires to the amp, the amp itself, or the subs/sub wiring. If no, the problem is the head unit--probably an internal short.
If the other amp works with the sub amp disconnected, reconnect the sub amp to the head unit, but disconnect the sub wires from the amp. Try the CD player. If the amp goes to protect with no speaker wires attached, the amp is bad. If the amp is OK, the problem is the subs or sub wires. Hook the wires up to the amp again, but disconnect them from the speakers. Try the player again. If the amp goes to protect, the problem is the amp wiring. If not, the problem is the subs. Check the impedance of each sub using an ohmmeter to determine which amp is out of spec.
Please let me know if you have questions, and thanks for using Fixya.

I have exactly the same problem, try a different speaker wire from your sub terminal to your amp terminal, if no luck you may have a loose connection on the wires on your sub, due to vibrations etc they can sometimes come loose, but very rare. worth checking though. 1 loose connection can make the amp go into protection mode. If all of these are fine, start from the beginning, ( I have tried this and i think its my speaker wire shorted out) 1st dissconnect all wires from amp. Then connect ground first, then your live. then power up amp, it it works andd not in protect mode your earth and live are fine, then connect your remote, then test, then speaker wire , then test, that way you can rule out bad connections and find any fault.

The "safe mode" on your amp usually kicks in for two reasons - the ohm load on the sub is too low for the amp (presenting a "short" to the amp), or it's going into thermal protection because the amp is too hot. From your description, it sounds like there's a short in the wire, the sub's ohm load is too low, or the sub is partially blown.

If you have another sub or speaker, connect it to the amp's output and see if the amp still goes into protection mode. If the amp goes into protection with a known-good speaker, then there may be something wrong with the amp's power supplies. If the amp works properly with another speaker or sub, then I would check the sub that's causing it to short out.

You may also want to check whether or not the amp is over heating by just touching the amp when it goes into protection. If it's just warm, that should be ok - if it's hot, then it might be working too hard. In this case, you may need to check the input voltage (12-14VDC) and the size of the power and ground cables. If your ground isn't properly connected, it can cause weird problems like over heating, shorts, erratic behavior, etc...

I am assuming the following: The Amp power is 1/0 gauge wire (huge) and runs directly to the fuse then to the battery + terminal, and you have a 1/0 gauge wire to an excellent ground. If you are missing any of these (esp the fuse) you are flirting with disaster. This Amplifier draws upwards of 100 Amps with a 1 ohm load! (If you are using this for competition you may also use a second battery to help dampen the noise, a high output alternator, and or a capacitor (which should be connected to the 4 gauge input terminals on your amp). I also assume that: When the engine isn't running the "humm" is not present, and when running if you remove the RCA connections from the AMP the noise should also go away. This amp has line level adaptability connecting speaker level inputs directly into the RCA terminals (you must set the "input sens" switch to "X10") ... so you may get rid of the PAC converter this may help get rid of the noise. For more info call MTX tech service at 800 CALL MTX. And please use ear protection at high levels ... trust me Tinnitus is no fun!

If you power up the amp with the RCAs plugged in, does it go into protection mode.

If you power up the amp with the RCAs plugged in, does the woofer pop?

sounds like the sub that throws it into protect mode is cross wired pull sub out and make sure they are wired right make sure ground from sub goes to ground on box and do same for power wire

try with one sub at a time to see if bad sub

If you have your subs wired to the amp in a bridged configuration, try wiring one to each stereo channel instead. Also, make sure your ground wire is secure and connected to a clean, solid metal part of the vehicle body with the paint scraped off. If this doesn't work, disconnect both subs and try connecting only one at a time; one of the subs may have a problem that is shutting down the amplifier.