Pre/Power Amplifiers

Where does the REF80S sit in the ARC performance landscape? Far quieter than the similarly-specified 75W GSi75 [HFN Jan '16] which featured the same complement of 6H30 double-triode drivers and KT150 output tubes – the latter was an integrated amp offering +33dB gain with a 76.8dB A-wtd S/N ratio (re. 0dBW) while the REF80S provides +24.7dB and a spectacularly wide 98.0dB S/N. In this respect it's up with the 6H30/KT120-equipped VT80 [HFN Oct '17] and REF75 [HFN Nov '12] before it, these offering the same +24.8dB gain (balanced input), wide 97.8dB S/N noise and >80dB stereo separation (20Hz-20kHz). All three amplifiers share the same (or very similar) output transformer with its usefully low 1.0-1.3ohm impedance, so the amp/speaker response is less influenced by loading.

Into 'flat' 8 and 4ohm loads the REF80S mirrors the REF75, VT80 and beefier KT150-equipped REF160S [HFN Feb '20] with an extended –0.3dB/20kHz and –4.0dB/100kHz response via 8 and 4ohm taps into 8/4ohm loads, respectively. There's a greater high-treble roll-off in Triode mode of –0.5dB/20kHz to –9.6dB/100kHz into 8ohm. Distortion, too, follows the trends we've seen in these earlier ARC amps at 0.017-0.095%/1W increasing to 0.095-0.88%/10W (UL mode, 20Hz-20kHz), and fractionally lower at 0.011-0.08%/1W in Triode mode [Graph 2, below]. Distortion increases gently with output, and at low bass frequencies through transformer core saturation. Power output also follows a predictable pattern – the REF80S achieving 2x80W into 8/4ohm loads (2x38W in Triode), increasing slightly to 85W into 8/4ohm and 140W/2ohm under dynamic conditions [Graph 1, below], the 9.6A current limit realised at 92W/1ohm. PM