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 | NAD C 388 has more power - 150W against 100W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Rogue Audio Sphinx v3 the better fit for desk or near-field listening, a small room and a mid-size room, and NAD C 388 for 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 | A | Rogue Audio Sphinx v3 holds up better into a 4-ohm load: its output nearly doubles to 200W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | B | NAD C 388 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Rogue Audio Sphinx v3 takes more analogue sources - 4 against 2. |
| Amplifier type | depends | Rogue Audio Sphinx v3 is Hybrid and NAD C 388 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. |
| Price | B | NAD C 388 costs less - $1,499 against $1,795 at list. |
| Watts per dollar | B | NAD C 388 is the cheaper watt - about $10 per watt against $18. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rogue Audio Sphinx v3 B NAD C 388
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?
NAD C 388 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 - Rogue Audio Sphinx v3 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Rogue Audio Sphinx v3 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.