Audio Research Reference 80S Tube Power Amplifier Lab Report

Lab Report

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


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 9.6A


Distortion vs. frequency (20Hz-20kHz, 10W, red; 5Hz-40kHz, 1W Ultralinear, green; Triode, black)

Power output (<1% THD, 8/4ohm) 79W (38W) / 80W (38W)
Dynamic power (<2% THD, 8/4/2/1ohm) 85W / 85W / 140W / 92W
Output imp. (20Hz–20kHz/60kHz) 1.04–1.30ohm / 2.06ohm
Freq. response (20Hz–20kHz/100kHz) +0.0dB to –0.3dB/–4.0dB
Input sensitivity (for 0dBW/70W) 165mV / 1395mV (balanced)
A-wtd S/N ratio (re. 0dBW/70W) 98.0dB / 116.5dB
Distortion (20Hz-20kHz, 10W/8ohm) 0.095–0.88%
Power consumption (Idle/Rated o/p) 211W / 400W
Dimensions (WHD) / Weight 470x260x470mm / 28kg
Price £14,998

Audio Research Corp
Minnesota, USA
Supplied by: Absolute Sounds Ltd
0208 971 3909