Pre/Power Amplifiers

Björn Erik Edvardsen (known as 'BEE'), the inspiration behind the original and wholly analogue 3020 amplifier from 1978, remains senior designer at NAD. In 2013 he identified Bruno Putzeys' 'Universal Class D' Hypex power amplifier modules as the ideal solution for the compact form factor of the first D 3020 [HFN Aug '14]. However, Edvardsen requested specific changes to accommodate higher dynamic power (voltage) and improved low impedance drive (higher current) to enhance the D 3020's compatibility with as wide a range of loudspeakers as possible. This, together with lower distortion, was achieved by changing the output FETs and reconstruction filter while combining a switchmode PSU with audio DSP to emulate the 'Soft Clipping' function of more traditional NAD amplifiers [see Lab Report, p71]. Although the D 3020 V2 includes digital inputs, and a DAC, its Hypex heart remains an analogue Class D design with a single-ended architecture that ensures its frequency response does not vary unpredictably with the undulating impedance of different loudspeakers. This is not something that all Class D amplifiers can claim... PM