Vintage

Boasting a full 22 transistors in its BOM (bill of materials), four of these are the 2SC1060 NPN silicon types, one pair for each channel, employed in Trio/Kenwood's quasi-complementary, AC-coupled output stage. Rated variously at 17W/8ohm or 2x13W/8ohm, our venerable sample of the KA-2002 mustered 2x12W into 8ohm and 2x14W into 4ohm, both just 1W shy of the original specification. Under dynamic conditions, output increased to 17W, 24W, 23W and 16W into 8, 4, 2 and 1ohm loads, respectively, [see Graph 1, below] and although these 10msec figures are more significantly lower than the 38W/8ohm dynamic output claimed by the brand at the time, Trio/Kenwood never specified duration or distortion for this latter figure.

Otherwise the KA-2002 performed as anticipated: overall gain is a sensible +36.6dB (40dB+ was more common) while the A-wtd S/N ratio proved about 10dB behind the 'modern average' at 75.5dB (re. 0dBW). Distortion increases gently with increasing output and decreasing frequency [see red infill, Graph 2], the former lifting from 0.15%/1W to 0.5%/5W and 1%/12W (all 1kHz into 8ohm). Distortion increases from 0.15%/1kHz to 0.28%/20Hz (all re. 0dBW) as a function of the capacitor-coupling, the latter impacting both output impedance (0.16ohm/1kHz to 1.2ohm/20Hz) and frequency response versus loading. Into 8ohm the bass response starts to roll away below 50Hz, reaching –2.8dB/20Hz, but is more extended at HF to –0.75dB/20kHz and –5.25dB/100kHz [black trace, Graph 2]. Low frequency extension is further limited by lower impedance loads [red, blue and green traces] although the 'loudness' contour delivers a +5dB boost at 50Hz and +2dB lift at 30kHz [dashed trace, Graph 2]. PM