Broken banana plug and stuck in amplifier

@jtcf has the answer. I have a set of dental tools in my tool box. I have used them multiple times with great success. I found mine at harbor freight a few years ago.

The rat tail file will do the job for sure.

Unplug it before you do anything.

@auronthas 

I have a couple of different sets of dental tools that I use for such things. Several of the tools have different size and angled points to get into small spots. You can get a cheap set at Harbor freight to start with.

All the best.

Any chance you can insert a drill bit that is smaller than the piece you are trying to remove? Wedge it in there and spray a small amount of WD40 to reduce any friction, then using pliers turn the bit to a point of engaging the banana piece the pull on the drill bit. If any movement is witnessed then repeat the process except the WD40 and it should work out a little at a time. 
if you use the rat tail file make sure to insert the tang in as the file is designed to cut on the push stroke and won’t engage the broken piece as you pull.

good luck