almarg 2)The miniDSP 2x4 has a very low input impedance of 6K.I'm going through the same impedance woes, with yet to arrive a Minidsp 2 x 4 HD to do some bass (<150hz) only experiments with, it's 10kohm input, a little higher than the 2x4.
I sent a email off to tech dept of mini dsp to see if the analogue inputs are a fet based input, if so then "maybe" the 10kohm smd load resistors can be swapped out for >50kohm?
This should be an easy way out if the source has high output impedance.
Cheers George