Turntables, Arms & Cartridges

Driven by the Imperium's biphase 17.8V PSU output, the SG-1's 24-pole AC motor and long belt (shiny side outwards!) achieve excellent speed stability – as supplied, the absolute speed was imperceptibly slow at –0.06% but this is well within the finest ±0.25% increment available for fine adjustment. Peak-wtd wow is just 0.02% with little or no drift and no dominant sidebands [see Graph 1, below]. The same is true of higher frequency flutter, also just 0.02% peak-wtd, where correlated speed variations are traded instead for innocuous noise. Furthermore, the phosphor bronze bearing sleeve, with hardened steel spindle running on a tungsten carbide ball, offers a low –70.5dB rumble (DIN-B wtd, re. 5cm/sec). We've seen lower [HFN Jul '22] but the efficacy of Vertere's removable spindle and air-rich/fibre mat is reflected in its far lower through-groove figures which, quite frankly, is where it really matters. Measured in-groove on the 3mm bonded acrylic platter surface this figure falls to –72.5dB, and further still to –74.5dB once the spindle is removed and mat introduced.

With the fine tracking force adjustment ring set midway down the partnering SG PTA HB tonearm's 'roll-wrapped' carbon-fibre tube, the principal resonant mode is deferred to a respectable 135Hz. There are also harmonic/torsional modes revealed at 290Hz, a complex cluster at 370Hz-540Hz and a single peak, possibly related to the titanium headshell fingerlift at 1.2kHz [see CSD waterfall, Graph 2]. Bearing friction/stiction is within 10mg in both planes while the underhang counterweight, low pivot point position and captive array of three silicon nitride balls all contribute to the inherent stability of the design even if it can never be entirely resistant to 'twisting'. PM