Truely Balanced Pre Amps


I was wondering if anyone could give me a list of truely balanced pre amps. Not just ones with a xlr inputs and outputs.
koiman
A 'fully balanced' preamp will not have the signal appear anywhere in the circuit in single-ended mode, except at an input. So all the switching, the volume control, EQ is all in the balanced domain.

So how many drop out when this rule is applied?
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