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 | A | Yamaha A-S1200 has more power - 90W against 70W into 8 ohms. That is about 1.1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | A | Yamaha A-S1200 holds up better into a 4-ohm load: its output increases strongly to 150W, where the other increases modestly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | Yamaha A-S1200 is the quieter design on paper - 110dB against 106dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Marantz Model 40n has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Streaming | B | Only Marantz Model 40n has AirPlay 2, Roon and HEOS. |
| Analogue inputs | A | Yamaha A-S1200 takes more analogue sources - 6 against 3. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | B | Marantz Model 40n costs less - $2,499 against $3,000 at list. |
A Yamaha A-S1200 B Marantz Model 40n
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?
The usual trade-off: Yamaha A-S1200 measures better, Marantz Model 40n costs about 17% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Yamaha A-S1200 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Yamaha A-S1200 becomes the more rational buy.
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.