Pre/Power Amplifiers

Why a tube preamp? The answer lies in one word – 'headroom'. The balanced outputs are capable of delivering over 60Vrms from a 300ohm source impedance (increasing to 450ohm/20Hz) while the input overload is in excess of 15V. So, just like the REF 6 [HFN May '16], the REF 6SE can be driven by any modern source and drive any modern power amp – having a standard 20kohm+ input impedance – with impunity. Sharing the same trio of Sovtech 6H30P double triodes per side as the REF 6, the overall gain (balanced in/out) of the REF 6SE is unchanged at +12.3dB as is the wide 96.4dB A-wtd S/N ratio (re. 0dBV). Distortion stays well within ARC's broad 0.01% specification but is uniformly higher (though not especially 'high') on the right channel above 330mV output – for example, just 0.0002-0.0007% (left) vs. 0.0012-0.0016% (right) from 20Hz-20kHz at 0dBV [see Graph 2].

Like the REF 5 and REF 6, the REF 6SE's response also varies with volume setting [see Graph 1, below] suggesting ARC's inter-stage buffering has not changed. The REF 6SE achieves its flattest response of –0.01dB/20kHz and –0.35dB/100kHz at full +12dB gain (103 on the display) but shows its most aggressive treble roll-off of –1.2dB/20kHz and –9.7dB/100kHz at +7dB gain (89). As the gain – not output level – is reduced still further the treble slowly picks up to achieve –0.9dB/20kHz and –8.4dB/100kHz at +6dB gain (86), –0.6dB/20kHz and –6.6dB/100kHz at 0dB gain (62) before reaching –0.14dB/20kHz and –3.0dB/100kHz at –6dB gain (41 on the display). Finally, reduced capacitive coupling within the REF 6SE has improved stereo separation to >100dB (20Hz-20kHz) in the REF 6SE versus >80dB for the REF 6. PM