Vintage

Technics’ ‘Computer Drive New Class A’ combines a dynamic bias adjustment regime with negative feedback to linearise the performance of its output stage in response both to signal transients and potential changes in (power) transistor temperature. It claims a very low 0.005% distortion across the full 20Hz-20kHz bandwidth up to a rated 40W/8ohm, a figure met in the midrange only at <0.005% up to 15W, increasing to 0.014% at 40W. Versus frequency [see Graph 2] the SU-V303 achieved a minimum 0.003% at 200Hz, increasing to 0.006%/20Hz and 0.019%/20kHz (all re. 10W/8ohm). It is likely that these figures were quoted for the power amp only, rather than the full integrated amplifier circuit with its +43.1dB overall gain and 83.5dB A-wtd S/N ratio (91dB IHF-A was specified).

Otherwise the SU-V303 comprehensively smashes its other ratings. Let’s start with the response – this meets its ±0.2dB from 20Hz-20kHz and extends to –1.7dB/100kHz, while the output impedance is far lower than Technics’ mere 60:1 damping factor might suggest at 0.023-0.053ohm (or 350:1 into 8ohm through the bass). Then there’s the maximum 2x45W and 2x50W power output at 1kHz into 8ohm and 4ohm, respectively. On the bench, some 40 years later, our SU-V303 achieved 2x52W/8ohm and 2x77W/4ohm at 1kHz/<1% THD, increasing still further under dynamic conditions – where ‘New Class A’ is in its element – to 79W, 138W, 204W and 250W into 8, 4, 2 and 1ohm loads, respectively [Graph 1]. That’s a maximum current of 15.8A (re. 1kHz/10msec/1% THD) to support the SU-V303 in its grappling with low impedance loudspeakers. Perhaps Technics should have focused more on the V303’s beef than vanishing distortion! PM