Integrated Amplifiers

While our tests of Luxman’s L-509X suggested a marked evolution over its predecessor, the L-590AXII, the differences between the former and its successor – the L-509Z reviewed here – are best posted under the heading of a ‘mild fettling’. The +43.5dB overall gain is unchanged as is the 85.6dB A-wtd S/N ratio (re. 0dBW) and power into 8/4ohm loads. For example, the L-509X delivered 2x155W/8ohm and 2x255W/ 4ohm with a dynamic output of 183W, 342W and 507W into 8, 4 and 2ohm, respectively, and limited by protection to ~300W/ 1ohm (16.7A). This compares with 2x152W/8ohm and 2x255W/ 4ohm from the newer L-509Z which has sufficient headroom for 178W and 335W into 8 and 4ohm loads under dynamic conditions but with tighter protection to 449W and 207W (14.4A) into the lowest 2 and 1ohm loads [see Graph 1, below].

What of distortion and Luxman’s new ‘LIFES’ compensation regime? Here’s where we see the refinement – the L-509Z’s distortion remains far steadier versus power output at ~0.002%/1kHz from 1W to the rated 120W while, versus frequency, THD is reduced from 0.0025%/20Hz to 0.00075%/20Hz (’X vs. ’Z) and from 0.0035%/1kHz to 0.0016%/1kHz (’X vs. ’Z) before closing to 0.035%/20kHz (both ’X and ’Z), all at 10W/8ohm [see Graph 2, below]. Any redistribution of feedback looks not to extend to the final output stage because its source impedance is identical at 0.021-0.052ohm (20Hz-20kHz) just as the response shows only the mildest uptick at ultrasonic freqs. (–3.2dB vs. –4.6dB/100kHz, ’Z vs. ’X). Stereo separation can provide an indication of changes to layout (capacitive coupling) but, again, this is unchanged at 82dB/1kHz and 60dB/20kHz. PM