Krell’s “XD” (Xtended Dynamics, Xtended Dimensionality, Xtended Detail) upgrade for the iBias amplifiers takes an already great sounding amplifier and raises its performance to the next level. “XD” is a classic example of Krell’s continuous R&D efforts reaping benefits across multiple product lines. During the development of the K-300i Integrated Amplifier, we discovered substantial sonic improvements by lowering the output impedance below traditional norms. So we applied this technique to our existing line of amplifiers and the improvement was so substantial that it required a unique designation, hence, “XD.”
It was no simple matter to just lower the output impedance. This affects the amplifier’s stability and transient response so each stage prior to the output stage had to be re-tuned to work optimally with the lower output impedance. This lower output impedance exerts more control over the speaker drivers and damps out unwanted vibrational modes, allowing more accurate reproduction of the original signal.