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: Luxman’s L-590 A-II integrated amplifier operates in pure class A for all stages and outputs 30 watts into 8 and 60 into 4 ohms. Its appearance is relatively similar to the smaller L-550A but certain differences are immediately apparent. The front hides most its knobs and controls behind a drop-down panel whereas the L-550A leaves them unconcealed. The two pairs of speaker terminals on the back are of a higher quality than with the L-550A.

When the A+B function is engaged, Takasina capacitors switch in to parallel the outputs for bi-wiring a single pair of speakers. A clever line phase sensor confirms proper AC polarity. If your AC wall outlet is incorrectly wired with the live and neutral lines inverted, a yellow LED says so.

The D-06 SACD player has the same facility and believe me, it’s not a frilly gadget function but of great help when chasing superior sound quality. A final detail is the new pre-out/main-in cable jumper to replace the L-550AII’s bridge pins. This new connection is higher quality but it is still possible to upgrade further with Acrolink jumpers.

Beyond these immediately visible differences, the internal design has more. The L-590 A-II benefits from a more sophisticated power supply. Luxman’s implementation of class A is not among those of lowest efficiency and on the contrary was carefully optimized. Compared to the L-550A-II, the power supply reservoir and transformer was increased to deliver power into lower impedance loads (680VA vs 540VA).

Most importantly, the L-590 A-II couples its power transformer output by copper bus bar to the circuitry. Eliminating the usual connectors, power line impedance is linearized, the noise floor lowered and dynamic range increased. With 25% more current capacity, the taller brother also offers 50% more output power.

The L-590 AII’s insides are divided into different chambers separated by rigid metal plates. In the center is the power supply with a big EI transformer with discrete windings for the left and right preamp and output stages respectively while the protection circuits and VU meters run off their own power supply. The output stage power supply sports four big Luxman-branded electrolytic filter capacitors and two big rectifying bridges with high-speed Schottky barrier diodes. This module doesn’t couple to the bottom cover but an inner shell that functions as extra shield and vibration damper. On either side of this section are the output buffers whose PCBs screwed tightly to the heat sinks. Luxman also paid attention to the AC input with a high-purity brass IEC which non-magnetic nickel plating and a final gold skin for lower contact resistance.

Each mono amp runs two pairs of power transistors in class A push-pull to fulfil the modest power rating. The preamplifier section mounts on two vertical PCBs to the back plate. Here a second PCB houses the LECUA volume control circuit based on JRC chips which switch a resistor matrix to insert one resistor per channel into the signal path. This is controlled by a black Alps potentiometer mounted on the front panel which acts as mere reference encoder for the chips. The overall circuit is not balanced and the XLR input signal is immediately 'de-symmetrized'.

The L-590 A II benefits from the new electronic selector switch of the C-1000f preamp which won the 2006 Grand Prix Award of Stereo Sound magazine in Japan. With this part, sound quality deterioration is claimed to be reduced to the minimum while channel separation and cross talk suppression were substantially improved over the previous L-550 A and L-590 A models. This machine also uses Luxman’s patented negative feedback circuit called Only Distortion Negative Feedback (ODNF) in its 2.2A version. This scheme only returns distortion to the input, not the full signal and works "by isolating noise and distortion at the output from the music signal and sparingly applying negative feedback to suppress them." The benefits are aid to be high phase fidelity, high slew rate (speed), low distortion and no need for a DC servo to improve overall sound quality.

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