Siblings in Yamaha's A-S range, so they share a design and a house sound. It comes down to power, features and price.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 90W against 85W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Noise floor | A | Yamaha A-S1200 is the quieter design on paper - 110dB against 99dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Yamaha A-S501 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | evenly matched | The same number of line-level inputs (6). |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Yamaha A-S501 takes up about 19% less shelf area (1710cm² against 2123cm²), and it is 95mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Yamaha A-S501 costs less - $550 against $3,000 at list. |
| Watts per dollar | B | Yamaha A-S501 is the cheaper watt - about $6 per watt against $33. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Yamaha A-S1200 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?
Yamaha A-S501 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. 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. Think about the whole system: the roughly $2,450 saved by taking the cheaper one would buy better speakers or a subwoofer, and either does more for the sound than the difference between two competent amplifiers.
What a spec sheet cannot show: how either sounds with your speakers, how the interface feels 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.