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 | Musical Fidelity M2si has more power - 76W against 35W into 8 ohms. That is about 3.4dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Cayin Jazz 70 the better fit for desk or near-field listening and a small room, and Musical Fidelity M2si 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. |
| Grip on hard loads | B | Musical Fidelity M2si holds up better into a 4-ohm load: its output nearly doubles to 137W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | Cayin Jazz 70 is the quieter design on paper - 100dB against 96dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Cayin Jazz 70 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | B | Musical Fidelity M2si takes more analogue sources - 5 against 3. |
| Phono stage | depends | Musical Fidelity M2si has a built-in phono stage (MM) and Cayin Jazz 70 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. |
| Headphones | depends | Only Cayin Jazz 70 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier type | depends | Cayin Jazz 70 is Tube and Musical Fidelity M2si 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 | Cayin Jazz 70 takes up about 42% less shelf area (1014cm² against 1760cm²), and it is 62mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Musical Fidelity M2si costs less - $1,299 against $1,399 at list. |
| Watts per dollar | B | Musical Fidelity M2si is the cheaper watt - about $17 per watt against $40. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Cayin Jazz 70 B Musical Fidelity M2si
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?
Musical Fidelity M2si has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Musical Fidelity M2si is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. 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 - Musical Fidelity M2si has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 35 watts is already more than most people ever use, and the extra 41 watts would be headroom you pay for and never hear - we rate Musical Fidelity M2si poorly for near-field use for exactly that reason.
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.