In this article, I review the Muse HiFi M5 Ultra tube + transistor portable DAC/Amp. The M5 Ultra features a custom 6418 ES9038Q2M DAC chipset developed together with ESS Technology and dual JAN6418 military-grade NOS vacuum tubes. It’s priced at $299.

Disclaimer: This sample was provided by HiFiGo for an honest review. All observations and opinions here are my own, based on my experience with the product.

Muse HiFi M5 Ultra

In the Box

• Muse HiFi M5 Ultra
• Charging cable
• Type C to Lightning cable
• Type C to Type C cable
• USB-C to USB-A adapter
• Leather protective case

Features

There’s a lot to unpack here with this little device. First of all, it has a dual-mode transistor + vacuum tube amplification that you can switch between at will. It’s loaded with a Qualcomm QCC5125 for Bluetooth connectivity that supports LDAC and aptX Adaptive. In addition to Bluetooth, the M5 Ultra can be connected to a phone or PC via USB.

M5 Ultra is outfitted with dual American RaytheonRAYTHEON JAN6418 military-grade miniature direct-heated pentode NOS vacuum tubes. In the past, implementing these tubes in portable devices has been problematic due to the microphonic effects that cause unpleasant ringing noises. But Muse HiFi has developed a unique shock-absorber solution that eliminates the stethoscope effect.

Then there’s the custom 6418 variant of the ES9038Q2M DAC chip. Muse HiFi worked together with ESS Technology to implement measures to minimize radio frequency interference (RFI) between JAN6418 Tubes and Bluetooth signals. Not only does it remove any background noise but now you can even make calls in tube mode.

Powering the unit is a 3000mAH battery with a rated durability of over 10 hours. It supports fast charging protocols such as QC4.0 and PD Fast-Charging.

Design

Muse HiFi M5 Ultra has a classy grey aluminium chassis with a smooth matte finish. It has glass panels on the front and back. The first thing that catches your eye is the PCB and circuitry visible beneath the front glass cover.

A small display is located at the top of the front panel. It shows the selected input, volume level, gain mode, digital filter mode, battery level, bitrate and sound mode (vacuum or transistor). The display can be switched off with a short press of the power button. Interestingly, turning Off the display locks all of the control buttons. I found this feature handy for certain situations but for the most part, I left the display turned On because it didn’t seem to affect the battery life.

Those buttons on the right side are (from top to bottom): Power On/Off, Volume Up, Volume Down, Menu Select+Play/Pause, Next Track and Previous Track. The buttons are relatively sensitive but they have a reassuring tactile click.

At the bottom are the 3.5mm and 4.4mm headphone outputs, a USB-C port for data and a separate USB-C port for charging. You can enjoy uninterrupted use with the M5 Ultra, whether it’s plugged in or running on battery power.

The left panel of the Muse HiFi M5 Ultra has an intricately patterned perforated panel. It looks good at any time but it looks especially sweet when the unit is powered on and in VT (vacuum tube) mode. The soft orange glow of the JAN6418 tubes behind the grille looks fantastic and adds to the overall user experience.

Bluetooth Performance

I found the Bluetooth performance to be consistent and reliable. I noticed the cutout distance was shorter than some of my other BT devices. However, during my normal use with both the M5 Ultra and my phone either in pockets or on the desktop, the connection was perfect, even in Tube Mode.

Sound

I tested the Muse HiFi M5 Ultra with various headphones and IEMs, including the FiiO FT1, Sennheiser HD650, Spiral Ear SE6 Nebula and DITA Project M.

Transistor Mode

In this mode, the M5 Ultra sounds pretty much as you’d expect – to my ears, the 6418 ES9038Q2M DAC sounds the same as the standard edition. It has a detailed and precise sound with well-defined instruments and vocals. It’s got great dynamic range and SNR, giving it a clean and transparent sound.

I love this mode for critical listening or for pairing with certain warmer headphones, where the extra clinical precision pays benefits. This is perfect for when you want to hear an uncoloured and analytical sound or when you’re looking for neutrality.

The bass response is tight and controlled, rendering fast, punchy notes. The mids are transparent and well-defined, offering clear vocals and instruments without any muddiness. Treble is crisp and detailed, producing precise and highly resolving sound, making it ideal for accuracy and micro-detail retrieval.

Tube Mode

This is where the Muse HiFi M5 Ultra gets really interesting. After switching to tube mode, music notes gain body and dimensionality. Ultra-sharp or sterile modern digital recordings suddenly sound more analogue and musical. Everything becomes smoother, especially in the midrange, where vocals and instruments sound more lush and lifelike.

The mild second-order harmonic distortion (that’s the good kind) sounds more pleasant, adding a sense of depth and character to the music. Bass notes gain extra body and weight. Mids gain an added sense of fluidity and engagement that the solid-state mode can’t quite replicate. The warmth of the tubes slightly softens the treble, resulting in a sound that’s both immersive and musical.

There’s a certain magic in the way it transforms recordings, making even familiar tracks feel fresh and engaging. The soundstage opens up, with instruments and vocals appearing more three-dimensional, giving the music a sense of space and presence that solid-state modes often struggle to achieve. The M5 Ultra’s tube mode enhances the music in a way that feels intimate and captivating.

Select Pairings (Tube Mode)

Spiral Ear SE6 Nebula: (3.5mm Low gain, volume 35-40) The sound becomes less intense and demanding on the listener than most solid-state amps. Don’t get me wrong, this IEM still sounds incredibly resolving and high-fidelity but with the tubes, it sounds smoother and more fluid. There’s added warmth that sounds more natural and cozy, less clinical and analytical. The upper mids still have an edginess, due to the Nebula’s tuning but it’s easier to deal with than it is in transistor mode.

DITA Project M: (3.5mm Low gain, volume 40-45) When an IEM has as much clarity (and neutral-bright character) as the Project M, pairing it with a tube amp can work wonders. Paired with the M5 Ultra, Project M is more forgiving on poor recordings. Instruments and vocals gain more note size and fullness. Bass notes sound slightly thicker and weightier but still maintain good definition and texture. The treble (which some people find edgy on this IEM) sounds softer and more even with extra warmth.

Sennheiser HD650: (4.4mm High gain, volume 60-70) Despite its warmer tuning, the HD650 still sounds nice and clear. The bass gains more depth but maintains good definition. Vocals sound articulate but slightly romanticized and more immersive. The treble is smooth and airy but is slightly more diffuse. Soundstage width is increased and reaches outside of the headspace. Imaging and placement are still precise.

Verdict

The Muse HiFi M5 Ultra is an innovative product with excellent build quality and functionality. It’s super cool to have a portable DAC/Amp with both vacuum tubes and Bluetooth whether I’m on the go, sitting around the house or enjoying music in a coffee shop. The audio quality is outstanding and Muse HiFi have done an incredible job of eliminating 100% of the microphonic or stethoscopic issues in tube mode thanks to their shock-absorption technology. Given its high quality and reasonable price, I think this product is a worthy candidate for our recommended award.