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 | 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 | B | Cambridge CXA81 II is the quieter design on paper - 105dB against 102dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Cambridge CXA81 II goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | A | Only Bluesound POWERNODE N331 has AirPlay 2 and BluOS. |
| Analogue inputs | B | Cambridge CXA81 II takes more analogue sources - 5 against 2. |
| Use with a TV | depends | Only Bluesound POWERNODE N331 has HDMI eARC, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | Bluesound POWERNODE N331 is Class D and Cambridge CXA81 II 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 | Bluesound POWERNODE N331 takes up about 74% less shelf area (418cm² against 1595cm²), and it is 180mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Cambridge CXA81 II costs less - $1,199 against $1,299 at list. |
A Bluesound POWERNODE N331 B Cambridge CXA81 II
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?
Cambridge CXA81 II has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If this sits under a television, Bluesound POWERNODE N331 is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.