Integrated Amplifiers

Many tube amplifiers offer the choice between Ultralinear and Triode operation but Icon Audio goes one step further here in providing a choice of overall feedback level. Although the amplifier's power output is unchanged, the 40 MkIV's 'Low Sensitivity' (higher feedback) mode offers a lower output impedance (0.3ohm versus 1.14ohm) compared with its 'High Sensitivity' (low feedback) mode, ensuring the amp/speaker system response is more predictable.

Overall gain is necessarily lower (+26.6dB vs. +35.8dB) but this makes 'Low' ideal for use with today's 2V+ digital line sources. Distortion is also much lower at 0.007%/1W, 0.05%/10W and 0.5%/50W (black trace) vs. 0.02%/0.18%/1.1% (red trace) – see inset Graph. Distortion is lower at the bass/treble extremes too (0.2%/20Hz and 0.36%/20kHz at 10W/8ohm vs. 0.9%/0.95%). Moreover 'Low' also offers the wider A-wtd S/N ratio (92dB vs. 85dB re. 0dBW). So the 'Low' gain/moderate feedback option would seem to hold all the performance cards. But I wonder how many listeners will actually prefer the 'High' gain/low feedback mode for sound? PM