Pro-Ject Audio Automat A1 Turntable Package Lab Report

Lab Report

While the A1's auto-start/lift/lower mechanism operates with slick efficiency – and without influencing the deck's playback performance – I am bound to say that the underlying speed stability and mechanical rumble/hum is not especially illustrative of Pro-Ject's 'finest hour'. Leave that to its manual decks like the Debut PRO [HFN Sep '21], for the A1 is built to a budget and to tolerances that Pro-Ject itself graciously acknowledges. It specifies a W&F of 0.27%, drift of ±0.75% and an 'S/N' of 65dB – none of these figures supplied with qualifying parameters but all in the ballpark of what I obtained on the bench. So, absolute speed was +0.8% fast in our sample (providing some wiggle-room for the motor to slow with age), while the peak-wtd wow clocked up a full 0.21% courtesy of a series of ±2-3Hz sidebands [see Graph 1, below]. The total peak-wtd W&F is ~0.3%. Rumble looks poorer than Pro-Ject might indicate, although the through-groove/through-bearing figure of ~61.3dB (DIN-B wtd re. 1kHz/5cm/sec) is influenced by high 50Hz, 150Hz, etc, hum breakthrough. Spectral analysis indicates that the mechanical rumble is closer to a more respectable 66-67dB.

The 8.3in tonearm is a 211mm effective length/low effective mass design, built to suit the 25cu compliance of the OM10. A fixed counterweight reduces complexity just as the bearing is basic and free of obvious 'chatter', but the main alloy tube is not well damped. Thus the primary bending mode is elevated to a high 200Hz but there are harmonic and torsional resonances at 270Hz, 410Hz and 625Hz followed by higher-Q/short-lived modes from 800-1.2kHz, the latter possibly associated with the carbon-reinforced headshell [see waterfall, below]. 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 33.6rpm (+0.8%)
Time to audible stabilisation 3-4sec
Peak Wow/Flutter (Peak wtd) 0.21% / 0.09%
Rumble (silent groove, DIN B wtd) –61.4dB
Rumble (through bearing, DIN B wtd) –61.2dB
Hum & Noise (unwtd, rel. to 5cm/sec) –46.8dB
Power Consumption 2W (1W standby)
Dimensions (WHD, with lid) / Weight 430x130x365mm / 5.6kg
Price £369 (inc. arm and cartridge)

Pro-Ject Audio Systems
Supplied by: Henley Audio Ltd, UK
01235 511166