A valve amplifier against a solid-state one. They are not really rivals: they differ in character, in what they will drive and in what owning them involves, so start there rather than with the watts.
| Area | Better | Why |
|---|
| Power | B | Cambridge CXA81 II has more power - 80W against 10W into 8 ohms. That is about 9dB - a different class of amplifier rather than a bigger version of the same one, and far more than most rooms will ever ask for. |
| Room size | depends | We rate Layer Audio Design Gen-300B the better fit for desk or near-field listening and a small room, and Cambridge CXA81 II for a mid-size room, a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | B | Cambridge CXA81 II has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | B | Cambridge CXA81 II takes more analogue sources - 5 against 2. |
| Amplifier type | depends | Layer Audio Design Gen-300B is Tube and Cambridge CXA81 II is Solid State. Valve designs are usually warmer and softer at the limits and need their tubes replaced eventually; solid state is the lower-maintenance choice. This is a taste and ownership decision, not a quality one. |
| Shelf space | depends | Layer Audio Design Gen-300B takes up about 44% less shelf area (888cm² against 1595cm²), and it is 105mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Cambridge CXA81 II costs less - $1,199 against $1,499 at list. |
| Watts per dollar | B | Cambridge CXA81 II is the cheaper watt - about $15 per watt against $150. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Layer Audio Design Gen-300B 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 is the easier recommendation: it leads on most of the measured areas and costs less. Take Layer Audio Design Gen-300B if one of the "depends" rows above describes your system. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - Cambridge CXA81 II has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 10 watts is already more than most people ever use, and the extra 70 watts would be headroom you pay for and never hear - we rate Cambridge CXA81 II poorly for near-field use for exactly that reason. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Layer Audio Design Gen-300B becomes the more rational buy.
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.