What is the Difference Between .1 and High Level Inputs?

There is a significant difference between these two connection methods. The .1 channel is a Special Effects Low Frequency Channel and has a relatively high (120 Hz, 4^th order) and aggressive crossover frequency. It should NEVER be used for any application other than a true LFE channel. The Low Level Input is, in fact, the same quality and filter type as our famous High Level Input, but in most instances can only handle 1 channel of the preamp-type signal being sent. Thus, it is useful in certain unusual applications (particularly difficult Class D amp connection, for example) to bypass the High Level Connection and use the Low Level Input.