Hi,

I don't know if such a thing exists for the linux audio world, but to get the effect of an exciter you basically need multiband dynamics. That is a compressor/ expander that works in multiple frequency bands which are separated by crossovers. You can even build it up yourself from single EQ and compressor plugins. Thats why I think there is no need to write an exciter plugin especially because there are a lot of exciters on the market which all cause different effects.

Greetz
Martin