Thorens TD 148A Turntable Lab Report

Lab Report

Unlike the semi-automatic TD 1601 [HFN Nov '20] which employs a synchronous AC motor, the fully-auto TD 148A uses a DC motor system that, bucking the trend for such solutions, suffers minimal low-rate speed drift while closely matching its AC-driven cousin with its impressively low wow and flutter – just 0.05% (peak-wtd). Higher frequency flutter components only amount to 0.03%, coinciding with the 20Hz/40Hz clusters seen on the rumble and W&F spectra [see Graph 1, below] but these and other modes between 80-120Hz and 140-170Hz push up the bearing rumble to a below-average –57.0dB (DIN-B wtd, re. 1kHz/5cm/sec). Fortunately this figure improves substantially to –65.6dB (through groove). I would endorse the supplied felt mat, but not advise using a clamp or LP weight with this deck.

The partnering TP95 tonearm is an evolution of the TP92 first fitted to the Perpetuum Ebner PE 4040 turntable [HFN Sep '17] and then upgraded in the Thorens TD 1601 [HFN Nov '20]. Unlike the TP92, the TP95 combines a rear counterweight with spring-loaded downforce, but this under-reads by 30% (so 1g = 0.7g in practice). The cold-drawn alloy tube still has a rubber/alloy ring situated midway along its length by way of controlling resonances, principal of which is the complex beam bending mode at a low 80Hz/105Hz with harmonic/twisting modes at 290Hz and 450Hz [see Graph 2]. The gimbal bearing enjoys low levels of friction (typically ~15mg) and betrays little or no play. The alloy cartridge platform bolted to the end of the light alloy tube increases its effective mass, but 10g remains ideal for the 18-20cu dynamic compliance of the supplied Ortofon 2M Blue, bringing the arm/cartridge resonance in at ~9Hz. 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 33.42rpm (+0.26%)
Time to audible stabilisation 2-3sec
Peak Wow/Flutter (Peak wtd) 0.02% / 0.03%
Rumble (silent groove, DIN B wtd) –65.6dB
Rumble (through bearing, DIN B wtd) –57.0dB
Hum & Noise (unwtd, rel. to 5cm/sec) –54.4dB
Power Consumption 2W (1W standby)
Dimensions (WHD) / Weight 430x140x370mm / 7.9kg
Price £1500

Thorens GmbH
Bergisch Gladbach, Germany
Supplied by: Signature Audio Systems
07738 007776