Mark at Rogue seemed surprised by the numbers I quoted him from the Stereophile review. He suggested bypassing a capacitor that he put in place to keep from sending DC power to the amp. Haha. So I’m not sure if he’s even confident in the design. I mean, do we sacrifice protection in the circuit so we can use off-the-shelf amps? With so many amplifiers at 20k, it’s strange to me. I do know that I will not be grabbing a soldering iron to bypass a capacitor in a $2500 preamp.
In the end he recommended an amplifier with an input impedance above 50k. Seems like I found that in the Parasound specs.