Induction loop resistance calculation
A good rule of thumb to remember is that 1m length of 1mm2 area copper wire has a resistance of about 17mohm at room temperature.

Your 14m of wire (1mm thickness, do you mean diameter?, if so area 0.785mm2) will have a resistance of about 17m * 14 / 0.785 = 0.3 ohms.

As far as the amplifier is concerned, that's pretty much a dead short, compared to the load it wants to see, in the 4 to 8 ohm range.

You therefore need a 10W resistor in the 4 to 8 ohm range, in series with your loop. This will limit the current to what the amplifier expects.