The 1/4" inputs 1 and 2 can receive a Line Level signal (i.e. +4dBu or -10dBV) from devices such as keyboards, drum machines, iPhones, etc. The following are the input level specifications for the 1/4" inputs:
Nominal Input Level:
INPUT jacks 1 and 2 (TRS phone type): -44 to +4 dBu
Maximum Input Level:
+18 dBu