Hi Rhyno,
That is correct, there where no change in sound out of the power amps with the Dukes plugged in or not. My resident power cords are ESP Referance, PAD Dominus Ferrox and Venustas.
I listen at various times during the days and nites, evert day of the week with the same results. I think my Pass 350.5s does not mate very well with the Duke. And because of this I plugged my pre and cdp into the Dukes with fantastic low level detail improvements.
Terry