The 0.5 Volt sensitivity is an older European standard that Quad adhered to for longer than other brands. These days, with 2 Volt as the Redbook CD output standard, it is effectively obsolete, but easily dealt with. We have something similar and more problematic with analogue pre amplifier inputs. Many of those are far more sensitive than the modern 2 Volt standard of CD players and many DACs. The result is that - depending on the input circuitry - you can get clipping on these inputs (the Naim sound). It was not for nothing that at the time of CD's introduction, Quad introduced a special low sensitivity input board for its pre-amplifiers to match the hot ouput of CD.