I used the PL Prologue Premium with KEF dynamic speakers and high efficiency Klipsch La Scallas. The hum is there in both cases although more pronounced with the Klipsch. The hum (60 hz I’m guessing) is constant, in both channels, and does not vary with volume or electrical circuit (yes, I've tried a cheater plug). It occurs on all inputs. If I had to guess, I’d say that some shielding was omitted during assembly. I’m planning to send to Upscale Audio for evaluation (unit is under warranty). I’ve heard from multiple PL owners who claim their units are dead quiet. I hope this is a fixable fluke.
