Muse HiFi M3 Ultra

Sonic Compass does not grade gear. We plot gear and listeners on the same seven axes, so a review tells you where a product sits and you can see how far that is from where you sit.

The Muse HiFi M3 Ultra is a pocket USB DAC/amp built around two real Raytheon JAN6418 vacuum tubes. I love tubes, and I own and have owned plenty of tube amps. I thank Muse HiFi in the video for the unit.

I drove it with the JM Audio XTC 2.5 Xtreme Trip closed-backs, an Erzetich headphone, the HiFiMAN HE6se V2 and the Luxear Valor IEM, mostly from the 4.4mm balanced output, with EDM, electronic, pop, classical and metal.

Where the M3 Ultra sits — Warm and rich, but not syrupy or wet. The strongest axes are Comfort and Emotional Engagement.

Vocals and mids — The JAN6418 tubes add a delicate warmth to vocals. Tube amps, and I have had many, often push the mid-range forward at the expense of the mid-bass and sometimes the sub-bass. This one doesn't, and I don't know how.

Treble — Detailed with no harshness or sibilance, however loud I went. There is a lovely smoothness, but still plenty of treble information. My JM Audio and Erzetich headphones have a lot of detail and resolution, and I didn't feel I was missing any with the M3 Ultra. I could listen for six hours at a time without fatigue.

Bass — Tons of bass down low, and it thumped. Not bass cannons, but not that far off. It never got bloated or boomy and stayed low and out of the way.

Power — At 480mW through the 4.4mm output I could drive the HiFiMAN HE6se V2 to loud volumes at the level where I listen. There was no headroom left, though, as I was on full volume.

Noise floor — The background was black, dead silent, including with the Luxear Valor.

Design — A true hollow-tube design where you can see the glass glowing, with simple, premium-looking machined lines. There is no screen and only one control, for volume. It does nothing but decode and amplify, which suits me. It runs cool and barely drains the phone's battery.

Microphonics — Portable tube amps can ping when you step. Muse HiFi uses a triple anti-vibration package of silicone shock absorption, cancellation circuitry and adaptive noise reduction. I shook it like a cocktail shaker while walking and the audio stayed completely stable.

Pure tube, no switch — Unlike its bigger sibling, the M5 Ultra, and rivals such as the Cayin RU7, there is no solid-state bypass. You are on tubes all day.

Against the Fuzzy MD3 — I reviewed that magnetic dongle recently and loved its bling and visual tricks as well as its sound. The M3 Ultra has none of that, and I've enjoyed it just as much. That is all I compared.

Cons — My one worry is the exposed tubes. With no cover, I wondered whether a coin, a metal card wallet corner or something sharp in a pocket could touch and damage them. I raised it as a worry, not as something that happened.

Read this against your own profile — I love tubes and a warm, smooth, relaxed-but-detailed sound, and I listen to a mix of metal, EDM, pop and classical. If that is you, this fits. If you want a solid-state option on the same unit, or you'll carry it loose with keys and coins, it doesn't.

Honest limits — The video thanks Muse HiFi for the unit, but doesn't say whether it was a sample, a loan or bought. By ear only, with no measurements. Nothing was said about stage or imaging or about timing, so those axes sit at neutral. The comparison with the Fuzzy MD3 is a passing remark. Specs are Muse HiFi's.