Integrated Amplifiers

Nearly 40 years after Krell's iconic Class A power amps [HFN May '11] hit the high-end, the company looks to be offering far less 'brutal' designs. When its iBias output stage technology was introduced [HFN Oct '14] the company suggested it was doing its part to modernise flagship hi-fi, increasing its appeal to consumers who were not as accepting of bulky intrusions into their living spaces as dyed-in-the-wool audiophiles. Now, as then, Krell claims that its iBias circuit technique combines the 'sonic benefits of Class A operation without the heat and power consumption of traditional Class A designs'.

In practical terms, rather than maintain a constant, high standing current (or bias) in the output stage – the brute-force, but wasteful, Class A approach to eliminating NPN/PNP transistor crossover distortion – these iBias amplifiers spontaneously adjust the bias to suit the music signal. This sliding bias technology differs from Technics' 'New Class A' and JVC's 'Super-A' regimes promoted through the 1980s because, in the K-300i, bias is calculated from a direct measure of the current delivered by the output stage. As a result it incorporates your choice of speaker – with its distinctive sensitivity and impedance vs. frequency trend – into the calculation of required bias. PM