Shielding has nothing to do with it. Shielding will just increase the capacitance, which is not a good thing. Your problem is sibilance from poor conductor metallurgy. It is often perceived as high-freqency harshness or brightness. You need single crystal or perfect crystal conductors to eliminate this.
BTW - once you have good IC's and speaker cables, your components sibilance will probably stand-out, particularly CDP or Transport and DAC. Only mods will eliminate this.
BTW - once you have good IC's and speaker cables, your components sibilance will probably stand-out, particularly CDP or Transport and DAC. Only mods will eliminate this.