I do offer a analog Variable HP filter and are also working on a LP filter and some other filters also :-)
It has Line level In/Out so that it can be connected to a Line input on any Mixer/Preamp.
More info about it is here:
Bozure.com - HPF1
Short Test Videos of it + the Gain Trim and the Phono1 modules :
http://www.youtube.com/watch?v=8zsZJ7UajUU&feature=plcp
http://www.youtube.com/watch?v=dHkivbBvHY8&feature=plcp