What yogiboy and Al said. The ideal gain structure lets you run toward the end of your line stage's range - all things being equal (which they never are).
Now, from a noise floor perspective, it's possible that a step-up may help, but you'll be dealing with colorations (even with the best of step-ups) that are very possibly a trade-off you won't like. You will be getting into yet another area where component matching will be critical.
One overlooked attribute of a step-up transformer is that it works against you from a cable capacitance perspective. You will have 100 (for a 1:10) or 400 (for a 1:20) times increase in capacitance (the square of the turns ratio) which may or may not matter, but is something to consider when selecting an output cable for your step-up transformer.
So (to equivocate further), it depends ...
Cheers,
Thom @ Galibier Design
Now, from a noise floor perspective, it's possible that a step-up may help, but you'll be dealing with colorations (even with the best of step-ups) that are very possibly a trade-off you won't like. You will be getting into yet another area where component matching will be critical.
One overlooked attribute of a step-up transformer is that it works against you from a cable capacitance perspective. You will have 100 (for a 1:10) or 400 (for a 1:20) times increase in capacitance (the square of the turns ratio) which may or may not matter, but is something to consider when selecting an output cable for your step-up transformer.
So (to equivocate further), it depends ...
Cheers,
Thom @ Galibier Design