A valve amplifier against a solid-state one. They are not really rivals: they differ in character, in what they will drive and in what owning them involves, so start there rather than with the watts.
| Area | Better | Why |
|---|
| Power | B | Luxman L-507Z has more power - 110W against 70W into 8 ohms. That is about 2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Audio Research I/70 the better fit for a small room, and Luxman L-507Z for a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Analogue inputs | B | Luxman L-507Z takes more analogue sources - 5 against 4. |
| Phono stage | depends | Luxman L-507Z has a built-in phono stage (MM and MC) and Audio Research I/70 does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Amplifier type | depends | Audio Research I/70 is Tube and Luxman L-507Z is Solid State. Valve designs are usually warmer and softer at the limits and need their tubes replaced eventually; solid state is the lower-maintenance choice. This is a taste and ownership decision, not a quality one. |
| Price | A | Audio Research I/70 costs less - $9,950 against $10,495 at list. |
| Watts per dollar | B | Luxman L-507Z is the cheaper watt - about $95 per watt against $142. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Audio Research I/70 B Luxman L-507Z
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?
Luxman L-507Z leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Audio Research I/70 is the one to take if it does not. If you play records, Luxman L-507Z saves you buying a phono stage; if you do not, ignore that row entirely.
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.