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 | Bluesound POWERNODE N331 has more power - 100W against 80W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Noise floor | A | Arcam A15+ is the quieter design on paper - 106dB against 102dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board, but only Bluesound POWERNODE N331 handles DSD and MQA. |
| Streaming | B | Only Bluesound POWERNODE N331 has AirPlay 2, Roon and BluOS. |
| Analogue inputs | A | Arcam A15+ takes more analogue sources - 3 against 2. |
| Phono stage | depends | Arcam A15+ has a built-in phono stage (MM) and Bluesound POWERNODE N331 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 | B | Only Bluesound POWERNODE N331 offers a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | Arcam A15+ is Class A/B and Bluesound POWERNODE N331 is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Bluesound POWERNODE N331 takes up about 72% less shelf area (418cm² against 1483cm²), and it is 154mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Bluesound POWERNODE N331 costs less - $1,299 against $1,500 at list. |
| Watts per dollar | B | Bluesound POWERNODE N331 is the cheaper watt - about $13 per watt against $19. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Arcam A15+ B Bluesound POWERNODE N331
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?
Bluesound POWERNODE N331 is the easier recommendation: it leads on most of the measured areas and costs less. Take Arcam A15+ if one of the "depends" rows above describes your system. If you play records, Arcam A15+ 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.