Greetings, I posted a small audio sample https://soundcloud.com/positivevibes/knbasssample
you can hear the effect on the bass 13 seconds in.
Though I used the effect lightly on this track.. is that the effect your speaking about?
It's true that it's originally done by overdriving the input on a reverb , however with a lot of playing around you can get a similar effect in the box.
I spent many months playing with reverb plugins and different effects... The effect I use on my bass time to time is done by adding a filter, a quality distortion plugin and then a spring reverb plugin. I group them and put it on a return channel.. of course it's not going to be as "wet" as using hardware.. I am happy with it though