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 | Arcam SA45 has more power - 180W against 105W into 8 ohms. That is about 2.3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| 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 110dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Arcam SA45 goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | B | Only Arcam SA45 has AirPlay 2 and Chromecast. |
| Room to grow | B | Only Arcam SA45 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | Devialet Expert 140 Pro is ADH (Analog Digital Hybrid) and Arcam SA45 is Class G. Class G/H switches its supply rails to cut the heat a Class A/B design wastes. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Devialet Expert 140 Pro takes up about 15% less shelf area (1521cm² against 1796cm²). |
| Price | B | Arcam SA45 costs less - $5,500 against $6,500 at list. |
| Watts per dollar | B | Arcam SA45 is the cheaper watt - about $31 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 Arcam SA45
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?
Arcam SA45 is the easier recommendation: it leads on most of the measured areas and costs less. Take Devialet Expert 140 Pro if one of the "depends" rows above describes your system. 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 - Arcam SA45 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 75 watts would be headroom you pay for and never hear.
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.