Direct coupled with transformers is one way to go, but according to the builder of the Dude it has sonic disadvantages - and certainly in his design. Most amps have ample input impedance and only a few can cause some rolling off at the extremes. A Dude owner has his Dude mated with a Pass Labs 350.5 and loves the combo. That amp has an input impedance of 25k ohms I believe.
One can never underestimate the power of system matching regardless of how the piece was designed.
One can never underestimate the power of system matching regardless of how the piece was designed.