Sidebar 3: Measurements
Fig.1 Wow and flutter ref. 3150Hz tone at 5cm/s (plotted ±150Hz, 5Hz per minor division)
Fig.2 Unweighted rumble from DC-200Hz (with clamp, blue; without clamp, black) all ref. 1kHz at 5cm/s.
While Technics certainly fired the starting pistol on the 21st century's fledgling direct-drive revolution, VPI was still quick out of the blocks with its belt-free HW-40 40th Anniversary. The Avenger Direct uses the same nonferrous motor design with its claimed 2.68Nm/s torque, bringing the 24lb (11kg) platter, complete with peripheral ring clamp, up to speed in a little over 1s. Absolute speed was a mere 0.03% fast in the sample tested here, while the 0.02% peak wow and 0.03% peak flutter (fig.1) indicated some tightening of production tolerances over the HW-40. Pitch stability is clearly excellent. Through-groove rumble, on the other hand, is about 2dB higher than seen with the HW-40 at –71dB (DIN-B wtd) and slightly poorer again at –70dB with the LP weight in place (blue vs black infill, fig.2) but these are still fine figures.
Fig.3 Cumulative resonant decay spectrum, illustrating the tonearm's various bearing, pillar, and tube vibration modes 100Hz–10kHz over 40ms.
Also debuted with the HW-40, the partnering 12" FatBoy tonearm features a 3D-printed armtube and integral headshell mounted into a robust gimbal bearing that offers a very low 10mg friction. The lightweight polymer/resin tube material contributes to a medium-high 14gm effective mass, while its variable cross-section (a chamfered square at the bearing to a rounded triangle at the headshell) pushes the first bending resonance up to a high 130Hz (fig.3). Harmonic and/or torsional modes appear at 225Hz and 280Hz, followed by slightly higher-Q but short-lived modes at 470Hz, 550Hz, and 890Hz. The distribution of these resonances is not dissimilar to that observed with various carbon-fiber armtubes, but are generally better damped in the Fatboy by VPI's choice of tube material.—Paul Miller
