Both are Luxman, from different ranges - the engineering approach is shared and the differences are mostly in power, connectivity and price.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 110W against 100W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Room size | depends | We rate Luxman L-507Z the better fit for a large room and a very large room, and Luxman L-505Z for a small room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | A | Luxman L-507Z holds up better into a 4-ohm load: its output nearly doubles to 220W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (105dB vs 104dB). |
| Analogue inputs | evenly matched | The same number of line-level inputs (5). |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | B | Luxman L-505Z costs less - $6,995 against $10,495 at list. |
| Watts per dollar | B | Luxman L-505Z is the cheaper watt - about $70 per watt against $95. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Luxman L-507Z B Luxman L-505Z
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both amplifiers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Luxman L-507Z is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. Think about the whole system: the roughly $3,500 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
What a spec sheet cannot show: how either sounds with your speakers, how the controls feel day to day, and what the app is like to live with - which is where most all-in-one amplifiers are actually won or lost. Power figures are the manufacturers' own and are not measured to a common standard, so treat small differences as noise. If you can hear both, that will tell you more than any row above.