Based on my years of helping customers solve interfacing
problems of all sorts, connecting unbalanced outputs to balanced
inputs, and vice-versa, certainly ranks among the most common
and confusing of tasks for system integrators. Basically, two
issues must be dealt with. The first involves the different
signal operating levels between unbalanced (consumer) and
balanced (professional) equipment. The second involves making
the actual connections to transfer the signal while avoiding
“ground loop” noise problems. Signal operating and reference
levels are significantly different for consumer and professional
equipment. The consumer reference level is -10 dBV or 316 mV
rms, while the pro reference is +4 dBu or 1.228 V rrns.
Therefore, a voltage gain (for consumer outputs driving pro
inputs) or loss (for pro outputs driving consumer inputs) of 3.9
or about 12 dB is theoretically required. On the consumer to pro
side, a fair question might be “Why not use a step-up
transformer for this gain?” Several commercial pro