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 | Sonos Amp has more power - 125W against 85W into 8 ohms. That is about 1.7dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Sonos Amp the better fit for a large room and a very large room, and Yamaha A-S501 for a small room. Match the amplifier to the room you actually have, not the one you want. |
| Noise floor | A | Sonos Amp is the quieter design on paper - 116dB against 99dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Yamaha A-S501 goes higher - 192kHz against 44kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Sonos Amp has AirPlay 2. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | B | Yamaha A-S501 takes more analogue sources - 6 against 1. |
| Phono stage | depends | Yamaha A-S501 has a built-in phono stage (MM) and Sonos Amp 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. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only Yamaha A-S501 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Sonos Amp is Class D and Yamaha A-S501 is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Sonos Amp takes up about 70% less shelf area (518cm² against 1710cm²), and it is 155mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Yamaha A-S501 costs less - $550 against $699 at list. |
A Sonos Amp B Yamaha A-S501
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 you play records, Yamaha A-S501 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.