[Mike Rivers]

anahata wrote:

Doesn't the usual configuration for a balanced pad involve no ground
connection? In that case any common mode signal will hardly be
attenuated at all by the pad, and hence there will be negligible
unbalancing of it either.

It's not a matter of attenuation, it's a matter of the impedance that a
differential input sees when looking back at the source. There needs to
be the same impedance in each leg, and it still goes to ground (or
common) at the mic, unless you use a transformer. I'd have to think too
hard about it (and I won't try to argue with you) given tha the C451
has a transformer at its input. But my gut feeling is that if you put
unequal resistances in the two signal leads, in any case, the input
will still see unequal voltage drops from a common mode source and will
therefore have less common mode rejection.

Prove it to yourself that you don't have to worry about a balanced
attenuator if you wish. Doing it right is just good practice.