Question What is the difference between the TC 2240 model and the TC 2240 HS model

Most of the TC 2240 units are HS, but the first units to be produced were not labeled HS. The difference is basically 4 chips in the EQ section, which give better results for the high frequecies. However some "normal" TC 2240 may also have the HS chips inside, although they do not carry the HS label. To check it, you should open the lid, and see if 4 of the chips are marked TL074.