WOW!!!!. The NOS Mullard CV2493 KQDD/K tubes made a significant improvement to the sound of my system: OPPO-95, Audible Illusions M3A preamp, McCormack Deluxe Edition DNA 0.5 Amp, B&W P6 speakers with custom made outboard crossovers, XLO S2 Interconnects and XLO Ultra 6 speaker cables.