What is the HLI port on the MTX tna251 amplifier?

See if the videos help

https://www.google.com/search?q=mtx+terminator+tna251+RCA+sockets

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THE GREEN LIGHT SHOULD SHOW WHEN AMP IS POWER UP AN RED WHEN IN PROTECTION MODE

Try eBay Often available there from private sellers

CHECK YOU CONNECTION YOU MAY HAVE PUT WIRE TERMINAL WRONG AN THE AMP GOES TO PROTECTION CHECK ALL SPEAKER TOO

It is actually in the controller, if you turn the remote all the way down and press on the controller until the bass goes off, you will be able to turn the bass up and down with the remote, mine worked but stopped after a month, I tried adjusting the amp but then I noticed that if I wiggled the knob on the remote that it would work, I mashed mine until it worked again and velcroed it to my console sonibcan get it on and off easily.

How do I get my MTX Terminator TNA251 out of protection please. It's driving me crazy. Is the amp no good.

Try this link: http://www.retrevo.com/samples/MTX-manuals.html

I have the same sub combo. The problem is the amp is underpowered for the 2 MTX 12s, get a bigger amp and you should be fine.

High Level Inputs on the amplifier. (or speaker level) allow you to tap into the speaker level or already amplified level wiring from the head unit.

its just a power light to let you know its on