The functions of A-190-1 and A-190-4 are nearly the same (Midi In, Midi Out, CV1, CV2, Gate, Clock, Reset). But the operation of the A-190-4 has been improved because a 3-digit LED display is available. The current values of all parameters (like Midi channel, reference note, clock divider) can be read back and modified by means of up/down buttons. In addition A-190-4 is equipped with an USB interface and the external +5V supply is no longer available. Consequently the additional charges for the 5V adapter fall away.