Vintage

In common with the servo-driven, gimbal-suspended linear-tracking arm featured on the Technics SL-10 [HFN Apr '19], the 95mm (effective length) wand fitted to the HT-L70 also features an optoelectronic sensor to keep the lateral tracking error within a claimed ±0.1°. Movement in play is triggered by feedback from this 'contactless' optical system which must also cope with pressings of variable quality – spectrum analysis revealing the so-called 'bump/thump' as a momentary increase in the noise floor from ~10-40Hz [blue spectrum, Graph 2 below]. Its subjective impact will be influenced by the eccentricity of the record, and the LF music content, but it does not appear quite so obviously on the W&F spectrum [Graph 1, below] as it did with the SL-10.

Instead, while Hitachi's quartz-locked brushless/slotless/coreless DC motor brings the 296mm-diameter alloy platter up to 33.3rpm within 2-3secs (holding it to an absolute speed accuracy of –0.09%), the moderate 0.06% peak wow is dominated by ±3Hz sidebands. Any complex sidebands caused by the peak low frequency mode at ~13Hz [–60dB re. 1kHz/5cm/sec – blue trace, Graph 2] will likely be buried in the random/noise-like flutter shoulder of the main peak, this contributing to an aggregated peak-wtd flutter of 0.06%. Otherwise, the HT-L70's residual hum and noise is determined by both the proximity of Hitachi's electronics and susceptibility of the pick-up (an original MT-70 is fitted here), amounting to –78dBV, or –51.7dB relative to 1kHz/5cm/sec [black spectrum, Graph 2 below]. The through-groove rumble of –66.3dB (DIN-B wtd) is about average for the era but still a few dB shy of that achieved by the SL-10 with Technics' own DC motor. This motor also had the SL-10's platter up to speed about 1sec quicker... PM