Luxman L-505uX versus L-550Ax

FAQs | Applies to: Luxman L-505uX Integrated Amp, Luxman L-550AX Pure Class A Integrated Amp

I'm interested in purchasing an integrated amplifier. What are the key differences between the Luxman L-505uX and the Luxman L-550Ax?


Tonally both amplifiers are voiced the same.


The major difference between the two amps is that one runs in Class A and the other Class AB. The Class A amp runs hotter than Class AB, though not as hot as a similarly powered vacuum tube amp.


The Class A amp (L-550Ax) has a sweeter, more liquid mid-range and a more three dimensional soundstage is thrown; better suited to more neutral, resolving speakers.. While the Class AB amp (L-505uX) has slightly better defined & more articulate bass and is a little more dynamic; better suited to darker sounding speakers. In reality there is not a lot of differences between the two power output wise—the L-505uX is slightly more powerful, but not dramatically so; we are talking about a 1dB difference.


Both amps have the same features:

  • Both have almost the same internal build quality.
  • The L-550Ax & the L-505uX have MONO, SUBSONIC & LOUDNESS Filter switch on the remote control. Though the L-550uX does not actually have the MONO feature. Loudness is a wonderful feature for late night, quiet listening. It also has a few buttons that support the D-05/06/08 CD SACD players basic functions.
  • The L-550Ax & the L-505uX have a SEPARATE switch for splitting the preamp section from the amp section, for example the inclusion of a Home Theater Processor, where you use the amp in the L-505uX to drive the front L + R speakers, but control the volume from the HT Processor.
  • The L-550Ax & the L-505uX both have one balanced input.
  • The L-550Ax & the L-505uX both have a newly redesigned phono stage.
  • The L-550Ax & the L-505uX have a discrete volume control based on the C-1000f preamplifier – no moving parts, no tracking issues at low volume. Much more transparent sounding.
  • The L-550Ax & the L-505uX have ODNF 3.0 performs three passes of the audio signal, checking for noise & distortion, while the ODNF 2.1 in the older L-505u does two passes.


There are only a few differences between the two amps:

  • The L-550Ax has a beveled Lucite cover in front of the meters; the L-505uX has a simple plastic recessed cover over the meters.
  • The L-550Ax has yellow meters; the L-505u has blue meters.
  • The L-550Ax does run considerably warmer than the L-505u, if heat is a consideration then the L-505u would be a better choice, such as an amplifier stored in a closed cabinet.

The final decision should probably take into consideration which speakers you are using, the acoustics of your listening room and what kind of music you are going to listen to.

In Music,
Philip O'Hanlon

Applies to: Luxman L-505uX Integrated Amp, Luxman L-550AX Pure Class A Integrated Amp