The MTS series let’s you buy one all-tube amp or head and fill it with up to four different all-tube preamps to suit your style. There are 14 different pre-amp “flavors” to choose from. The tube preamps switch in and out in a way similar to a PCI or video card. You can actually switch between the installed preamps on the fly. If you would like images, please let me know and I’ll get them right to you. The MTS series has been available abroad and actually won a 2007 Innovation Award from the French publication “Audio Fanzine”