One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | B | NAD Masters Series M33 has more power - 200W against 105W into 8 ohms. That is about 2.8dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Devialet Expert 140 Pro the better fit for desk or near-field listening, a small room and a mid-size room, and NAD Masters Series M33 for a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Speaker load rating | A | Devialet Expert 140 Pro is rated down to 2 ohms against 4, so it is the safer partner for a low-impedance speaker. |
| Noise floor | A | Devialet Expert 140 Pro is the quieter design on paper - 130dB against 120dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | B | Only NAD Masters Series M33 has AirPlay 2 and BluOS. |
| Analogue inputs | B | NAD Masters Series M33 takes more analogue sources - 2 against 1. |
| Room to grow | B | Only NAD Masters Series M33 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Headphones | depends | Only NAD Masters Series M33 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Devialet Expert 140 Pro is ADH (Analog Digital Hybrid) and NAD Masters Series M33 is Class D. Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Devialet Expert 140 Pro takes up about 22% less shelf area (1521cm² against 1949cm²), and it is 51mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | NAD Masters Series M33 costs less - $5,999 against $6,500 at list. |
| Watts per dollar | B | NAD Masters Series M33 is the cheaper watt - about $30 per watt against $62. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Devialet Expert 140 Pro B NAD Masters Series M33
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?
NAD Masters Series M33 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - NAD Masters Series M33 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 105 watts is already more than most people ever use, and the extra 95 watts would be headroom you pay for and never hear - we rate NAD Masters Series M33 poorly for near-field use for exactly that reason.
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.