There are always alternative ways to skin a cat. The ‘chat noir’ of hi fi has always been ‘coherence’ – it is a creature occasionally alluded to, but mainly ignored. Which is a shame, because time coherence is as fundamental part of music reproduction as dynamic range. It’s not talked about because it is filed under too difficult. None the less, all the most musical speakers take into account phase coherence. Technics understand this, and with their new SU-G700 amplifier you get a time coherence ‘get out of jail free’ card, in the form of LAPC.
AND IT WORKS, MAKING ALMOST ANY SPEAKER TIME COHERENT
A very special amplifier for £1,799
LAPC (Load Adaptive Phase Calibration)
Speaker impedance changes with each frequency and a power amplifier is required to drive speakers without being affected by the speaker’s characteristics. However, conventional digital amplifiers are connected to speakers through a low-pass filter at the output stage, so they are even more strongly affected by the speaker impedance characteristics. Also, although the amplitude characteristics of conventional amplifiers due to negative feedback were improved, the phase characteristics could not be enhanced. We thus developed a speaker impedance adaptive optimisation algorithm that performs correction to the ideal impulse response through digital signal processing by measuring the frequency amplitude-phase characteristics of the amplifier with the speakers connected. This new technique enables flattening the frequency characteristics of amplitude and phase, which had previously not been achieved by amplifiers, as well as delivering a sound with rich spatial expression.