A signal converter, and more particularly, a mixer includes a quad diode race or bridge having a first signal supplied to a first pair of input ports in a balanced state, and a second signal supplied to another pair of input ports in an unbalanced state. The unbalanced connection to the diode race is effected via connections to conducting strips of a printed circuit board, and the balanced connection is effected by a hybrid balun element. The output from the circuit is derived from an input to the balun, at a low signal level.