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 | evenly matched | Effectively the same output - 75W against 85W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Noise floor | B | Yamaha A-S501 is the quieter design on paper - 99dB against 90dB. 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 | A | Only SVS Prime SoundBase has AirPlay 2, Chromecast and DTS Play-Fi. |
| Analogue inputs | B | Yamaha A-S501 takes more analogue sources - 6 against 2. |
| Phono stage | depends | Yamaha A-S501 has a built-in phono stage (MM) and SVS Prime SoundBase 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. |
| Amplifier class | depends | SVS Prime SoundBase 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 | SVS Prime SoundBase takes up about 70% less shelf area (517cm² against 1710cm²), and it is 169mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Yamaha A-S501 costs less - $550 against $699 at list. |
| Watts per dollar | B | Yamaha A-S501 is the cheaper watt - about $6 per watt against $9. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A SVS Prime SoundBase 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 is the easier recommendation: it leads on most of the measured areas and costs less. Take SVS Prime SoundBase if one of the "depends" rows above describes your system. 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.