L-590Ax Pure Class-A Integrated Amp

by Luxman
in Electronics

Luxman introduced the L-550A and L-590A in 2005, since then we have celebrated our 80th anniversary with commemorative components that have reaffirmed Luxman's status at the pinnacle of high-end audio. In these latest integrated models, the gorgeous texture and three-dimensional performance of our original Class A amplifiers has been retained and further refined. For example, the L-550A II amplifiers featured a new electronic selector switch, adopted from the input section of the C-1000f control amplifier; while the 'x' series now uses a variation of the LECUA discrete volume control first introduced in the C-1000f.

Chassis bases have superb vibration absorption in order to surpress noise levels. The power transformer, electrolytic capacitors and amplifier output stage (see amp block below) are laid out so as not to interfere with each other. To reduce interference further, the block construction isolates each section using shielding panels, and extensive internal filtering to reject magnetic flux interference.

Thanks to the always-on nature of the topology and  the removal of an entire type of distortion, allied to sound that excels in a midrange liquidity, low-level detail, superb dynamics and transparency, its devotees are more than happy to put up with low efficiency and heat. What Class A always seems to offer above everything else is a tube-like sound without the maintenance hassle of tubes.

The L-590Ax, L-550Ax and the L-509u, feature the new high quality electronic selector switch, which is the heart of the C-1000f pre-amp (one of Luxman’s 80th anniversary commemoration models). The sound quality deterioration using the new electronic input switch is now minimal, while channel separation and crosstalk efficiency were raised substantially in comparison with the L-550A / L-590A. In addition the illuminated position indicator around the input selector knob, makes it much easier to view the selected position even from afar.

The integrated amplifiers also benefit from the C1000f in that they use a variation of the LECUA 1000 volume control. At any single volume setting only a few resistors are in circuit per channel. The less devices in the signal path, the purer the sound, the cleaner the music.

At low listening levels, potentiometers have trouble keeping both channels in balance,  so one channel might easily be 3dB louder than the other. With the volume control made of discrete parts, this is no longer an issue. 

The amplifier section has not been ignored either; noise and distortion has been kept to a minimum with the introduction of ODNF version 3.0A. The deep, rich Class A tone is available here is Luxman’s hall-mark sound. More info on ODNF below.

Luxman nowadays use a distortion reduction circuit called Only Distortion Negative Feedback (ODNF). This system works by isolating noise & distortion at the output from the music signal and sparingly applying negative feedback to suppress them. Conventional negative feedback systems can have an adverse effect on the music, introducing phase distortion. "The circuit features such an ultra-wide range, ultra- high slew rate and ultra low distortion that it does not use phase compensation for the music signal amplifying circuits." This new technology also ensures that need for a DC servo circuit is alleviated, again improving sound quality.