VPI Prime 21+ Belt-driven Turntable Lab Report

Lab Report

While the Prime 21/21+ features a reinforced alloy/MDF chassis, its 9kg alloy platter, 24-pole AC-synchronous motor and inverted bearing (with hardened stainless shaft, chrome ball/PEEK thrust pad and phosphor bronze bushing) are familiar VPI staples derived from the original Prime model [HFN Jun '15]. As a result there are no particular surprises when it comes to wow and flutter or rumble. The former is a moderate 0.07% (peak-weighted) with a slightly higher 0.04% low-rate wow than we measured with the Prime [Graph 1, below] – a figure highly influenced by the motor position and belt tension. Absolute speed accuracy was –0.18% (centre pulley groove) while rumble, measured through its bearing, was substantially improved over the Prime with DIN-B wtd figures of –70.4dB (through-groove) and –69.6dB (through-bearing).

The partnering 10.5in arm features a '3D printed' tube and integral headshell mounted into a robust gimbal bearing assembly that combines a very low <10mg friction, in both planes, with no detectable play. The lightweight polymer tube material contributes to a low/medium 11g effective mass but it does not confer quite the same rigidity we saw with the variable cross-section geometry of the longer '3D printed' 12in JMW Fatboy tonearm [HFN Apr '19]. The 130Hz primary bending mode measured for that arm is reduced to a lower 85Hz here [off the X-axis, Graph 2] with harmonic and twisting modes at 170Hz and 300Hz, and more rapidly dissipated modes at 400Hz, 500Hz and 890Hz. The main 85Hz mode is very strong but the other resonances are generally better damped in this polymer/resin tube than, for example, most carbon-fibre types. PM


Wow and flutter re. 3150Hz tone at 5cm/sec (plotted ±150Hz, 5Hz per minor division)


Cumulative tonearm resonant decay spectrum, illustrating various bearing, pillar and 'tube' vibration modes spanning 100Hz-10kHz over 40msec

Turntable speed error at 33.33rpm 33.27rpm (–0.18%)
Time to audible stabilisation 3-4sec
Peak Wow/Flutter (Peak wtd) 0.04% / 0.03%
Rumble (silent groove, DIN B wtd) –70.5dB (–70.4dB with clamp)
Rumble (through bearing, DIN B wtd) –69.6dB
Hum & Noise (unwtd, rel. to 5cm/sec) –56.1dB
Power Consumption 6W (1W standby)
Dimensions (WHD) / Weight 535x190x400mm / 17.5kg
Prices £4500 (£6500 with Shyla cartridge/Weisline cable)

VPI Industries Inc.
New Jersey, USA
Supplied by: Renaissance Audio, Scotland
0131 555 3922