STST MOTUS Ⅱ/VERTEX

摘要

Unlike the very high-torque motor systems employed in many earlier direct-drive decks, which for pro duty were required to be up-to-speed in a half-revolution, the torque developed by STST's AC motor is sufficient to have the 6kg POM platter to 33.33rpm (33.31 rpm in this instance) within six seconds. Speed stability is excellent with a very low peak-weighted wow and flutter of just 0.04% [see Graph 1, below] although there's still some slight motor noise escaping up through the 'bearing' and spindle to realise a rumble figure of -66.7dB (DIN-B weighted). This is around 5dB higher than the very best decks but with only -68.0dB making it through to the (silent) vinyl groove, will not prove subjectively distracting. The partnering 10in version of STST's Vertex tonearm offers very low levels of friction but there was just a hint of play in those titanium gimbal bearings. The damped carbon-fibre armtube might suggest a low effective mass (like the Pro-Ject models) but the alloy headshell brings it to a medium figure of 11 g complete with the smaller of the two counterweights. Perhaps because of the added mass of the headshell, the main 125Hz beam mode is also slightly lower in frequency than Pro-Ject's full-carbon models, with a higher-Q secondary mode at 225Hz [see Graph 2]. Some of the smaller structures on the arm (bias flywheel and cueing arm) are probably responsible for the lower-level modes in the midband at 750Hz and 820Hz. Nevertheless this is a tidy enough looking result.