These are not the same size of amplifier: Yamaha A-S301 has roughly 2x the power of Technics SU-GX70. That is about 3dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | B | Yamaha A-S301 has more power - 60W against 30W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Technics SU-GX70 the better fit for desk or near-field listening, and Yamaha A-S301 for a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | A | Technics SU-GX70 holds up better into a 4-ohm load: its output nearly doubles to 60W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | A | Both decode on board, but only Technics SU-GX70 handles DSD. |
| Streaming | A | Only Technics SU-GX70 has AirPlay 2 and Chromecast. |
| Analogue inputs | B | Yamaha A-S301 takes more analogue sources - 6 against 2. |
| Room to grow | B | Only Yamaha A-S301 offers a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | Technics SU-GX70 is Class D and Yamaha A-S301 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. |
| Price | B | Yamaha A-S301 costs less - $350 against $1,999 at list. |
| Watts per dollar | B | Yamaha A-S301 is the cheaper watt - about $6 per watt against $67. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Technics SU-GX70 B Yamaha A-S301
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-S301 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 - Technics SU-GX70 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 - Yamaha A-S301 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 30 watts is already more than most people ever use, and the extra 30 watts would be headroom you pay for and never hear.
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.