Lotoo Mjolnir: Thunderstruck – A DAP Review

Page 1: Introduction, Unboxing and Accessories, Build and Design, Physical Controls, Battery Life
Page 2: Connectivity and Storage, Wireless Audio, GUI and Presentation, Navigation
Page 3: Sound Impressions and Power
Page 4: Select Comparisons, Verdict

Connectivity and Storage

Wireless streaming aside, which we’ll talk about in the next section, you can stream data to the Mjolnir digitally in these four formats:

• USB-C
• XLR (AES/EBU)
• RCA (SPDIF)
• Optical (SPDIF)

It’s worth noting that, when connecting a Windows or Mac machine to the Mjolnir via USB, you must use a USB-C to USB-C cable. Several Mjolnir users, myself included, have found issues when using a USB-A to USB-C cable, for example. So, if you’re planning on getting the Mjolnir as a desktop USB DAC, please make sure you have a USB-C port on your machine, as well as a USB-C to USB-C cable.

When a USB connection is detected, you’ll be given the option to go into Storage mode, where the Mjolnir enters an idle state, and you can transfer files to and from its internal SD card (with a max speed of around 300 MB/s), or into USB DAC mode, where the Mjolnir, again, goes into an idle state and acts as a DAC/amp for the attached transport.

For me, a huge issue here is you cannot enter or exit these modes freely through the software. Whichever of the two modes you choose, you’re stuck there until the USB device is disconnected. You can’t use the Mjolnir on its own when it’s connected via USB either, because simply connecting a USB device to it will force you into one of these two modes. I think this is extremely inconvenient. I’d love to be able to freely choose when to use the Mjolnir on its own, and when to use it as a USB DAC (or to add tracks to its SD card) without having to get up from my chair, reach around my desk, then plug or unplug a USB cable. I hope a fix for this is feasible through a firmware update.

Thankfully, however, this option is available when it comes to the other digital inputs. You can enter Digital In mode (which is unfortunately misspelled “Digtial” on the current firmware) through the Mjolnir’s secondary homepage to access the device’s optical, coaxial and AES/EBU inputs, then back out whenever you want to use the device on its own.

Sadly, there are some navigational issues here too. Out of the box, the Mjolnir has AES/EBU as its default digital input, and there isn’t an option to change that on the Digital In menu. What you have to do is access the drop-down menu, press More Options…, find the Digital Input button among the unused options, add it to the drop-down menu, press it, then change the input. As you can probably tell, the option is an utter chore to get to, and I probably wouldn’t have found it myself if I wasn’t reviewing it and pressing every possible button. In a future update, I’d love to see an input selector added to the Digital In menu, or, better yet, as a function on the F1/F2 switch. 

In terms of outputs, the Mjolnir’s digital ones are the same as the inputs listed above (except for USB-C, of course). And, for analog, you have the following balanced options:

1. 4.4mm
2. 4-pin XLR
3. 2x 3-pin XLR (Line Out)

As well as the following single-ended options:

1. 3.5mm
2. 6.35mm

Lastly, for storage, the Mjolnir has a full-sized SD card slot on the front, so it can act as its own transport. It accepts up to a 2TB card, and it’s capable of reaching speeds up to 300 MB/s with UHS-II compatibility. And, on the back, you’ll find a USB-A port, where you can connect an SSD or USB drive to act as your music library. Its max read speed there is 20 MB/s.

Wireless

The Mjolnir features a number of wireless protocols for audio input and output. Plus, it features Wi-Fi too. Besides streaming, this can also be used to update its firmware.

Bluetooth

The Mjolnir is capable of both Bluetooth input and output. For the former, all you have to do is press Bluetooth DAC on the secondary homepage, and the Mjolnir will become discoverable. And, to connect the Mjolnir to a Bluetooth speaker, for example, go to Settings, press Bluetooth, wait for your receiver’s name to appear, then press it. It’s the exact same process as connecting to a Bluetooth device from your smartphone.

Range to and from the Mjolnir is strong. I was able to move approximately 15 meters away from the device (without any obstructions) before I started to lose the feed. So, while, as we’ll explore in the next section, Bluetooth will not be how you get the absolute best sound out of the Mjolnir, it’s still there should you ever need it, and it’s a breeze to connect to and use as well.

LTTP

LTTP stands for Lotoo Tele-Transport Protocol, and it’s Lotoo’s proprietary wireless standard. It allows users to stream lossless audio wirelessly from an LTTP transmitter to the Mjolnir. Unfortunately, this feature is currently still in beta. Lotoo say it’ll come out “soon,” which is admittedly vague, and they’ll include this feature on all their future DAPs as well.

The transmitter I was sent is called the WT-1 dongle. It comes with both a Lightning and USB-C head, which you can interchangeably attach to the dongle’s body. Once you plug it in, it’ll power on and flash red-and-blue, meaning it’s searching for a pair. Once you connect to it in the Mjolnir (by going to the LTTP menu on the secondary homepage), the light will stay blue. It’ll turn red if you’re paired, but disconnected from the target device. The WT-1 also has what Lotoo call a function button on the side, but all it does now is set the dongle back into pairing mode. Perhaps, more functions (like Play/Pause, for example) can be integrated in the future.

In terms of looks and feel, I can’t help but be a bit letdown, to be honest. First off, the mismatch between the matte-black transmitter and the metallic-gray Mjolnir is puzzling. It looks indecisive from Lotoo as to which scheme they wanna stick to. I guess it’ll match when they start releasing matte-black DAPs that are LTTP compatible. The bigger issue, however, is the WT-1’s build. It has a distinctly plasticky feel to it, both in weight and how the paint almost absorbs the oils from your hands. It’s nowhere near the build quality of, say, their S1 or S2 dongles. While they’re far pricier items, I’d at least expect a similar caliber of chassis.

Another gripe I have is that the connector head is really tough to detach from the dongle. It lacks a mechanism to temporarily loosen the head like on one of those universal phone chargers, nor does it have a button that pushes the head out. I literally had to pry the heads out with my flexible iFixit tool to change them, and their plasticky finish chipped pretty easily in the process. So, I’d highly recommend Lotoo figure a solution out, if possible, to all these issues before they launch the WT-1.

In the LTTP menu, there’s also a High Quality switch for the music you’re streaming, which I assume you’d want to turn off if your main concern was the transmitting device’s battery life.

If I were to suggest anything, it’d be nice if we could rename the WT-1 on the Mjolnir’s LTTP menu. Right now, mine’s called LTTP-851560, and I’d love to be able to rename it. So, in a situation where, say, there are multiple WT-1 transmitter’s in one room, I can easily switch between sources, without having to recall whose transmitter was attached to what.

In terms of sound, when I compare streaming from my phone to the Mjolnir via Bluetooth and doing the same with LTTP, I’m hearing slightly improved technical performance and a different tonality on the latter. Bluetooth has tapered, smoothed-over sound with softer transients, a shallower background and a slightly smaller soundstage. LTTP, most notably, is sharper in tone; more articulate in the mid- and upper-treble. Then, it gives a deeper, blacker background, more focused, resolving transients and a wider stage. So, you do get higher-quality audio from the dongle, and it’s the medium to use if fidelity is your priority.

Now, compared to playing music directly off the Mjolnir’s SD card, I think you get a lusher, more refined sound there. The LTTP, by comparison, comes off a tiny bit raw around the edges, especially in the aforementioned mid- and upper-treble regions. Direct playback feels more effortless, and I’m hearing a bit more fullness – more body and weight – in the midrange as well. So, direct, wired audio remains king, but LTTP is the next best thing if wireless is a must.

Editorial note (11/20/2024): After some further testing, we’ve discovered issues with LTTP’s transmission when playing tracks with busier sections, especially in the uppermost-registers. When playing a song like ILLENEUM’s Blame Myself, there’s a noticeable fuzz to Tori Kelly’s vocals (especially on her consonants and sibilants), as well as the high-frequency wind (or “whooshing”) effects in the background. Then, during the track’s beat drops, where lots of high-frequency winds, wails and sizzles also come in, the transmission will stutter. I never encountered these issues previously, because none of my test tracks ever get this crowded. The issues virtually disappear when playing tracks that aren’t this busy, nor as upper-treble-rich. So, on my end, I’ll be adding this track to my test suite for future reviews, and, on Lotoo’s, I suggest they work on a fix via firmware update as soon as possible. My apologies for catching this issue late.

DLNA Streaming and Apple Airplay

The Mjolnir also accepts both DLNA and Apple Airplay as wireless inputs, both requiring the device to connect to the same WiFi network as the transport. Unfortunately, both are currently quite impractical to use, because the Mjolnir requires you to manually reconnect to the WiFi network every time you turn it on. It doesn’t automatically connect to networks in its database. You have to go to Settings, then to WLAN, then select a network it remembers (if in range, of course). This tedious process leaves Bluetooth and LTTP as far superior options for now, and that’ll remain the case until Lotoo fix this bug in a future update.

Once that process is done, though, AirPlay works perfectly fine. I’ve been able to stream music and YouTube audio smoothly on it. On the other hand, even after consulting Lotoo themselves, I haven’t been able to get DLNA to work. I understand it’s a protocol often used by Roon servers, so perhaps those who have them will be more adept at it. So, this will be the one feature the device has that I won’t fully delve into.

GUI and Presentation

If you’ve used one of Lotoo’s recent PAW players, you’ll be instantly familiar with the Mjolnir’s UI. It’s completely identical. The device uses Lotoo’s proprietary operating system, which also features a blazing fast boot, as well as snappy operation overall. On the home page, you’ll find the usual options: Five ways to access your library (Playlist, Album, Songs, Folders and Artist), the Settings menu, as well as the last-played track with playback control. You can also find the current states of Bluetooth, loop mode, battery, XRC, etc. at the top of the screen.

The Mjolnir also has a secondary homepage you can access by swiping from right to left. From here, you can access the Mjolnir’s many forms of digital streaming: Roon, Apple Airplay, LTTP, Bluetooth DAC, DLNA and Digital In (again, unfortunately misspelled “Digtial” on the current firmware). Roon is grayed out at the time of writing, so I assume it’ll come in a future firmware update.

When in Digital In or USB DAC mode, what you’ll see on the screen are the format, sample rate, bitrate and levels of the audio it’s processing, as well as the options to apply XRC (which is Lotoo’s PCM upsampling feature) and EFX (i.e. PMEQ and ATE, which we’ll talk about later).

As I’ve said in my previous PAW reviews, I think Lotoo’s UI is probably the best non-Android one on the market. I find Android offerings tend to have thinner, cleaner fonts that better show off the screen’s sharpness, but that’s a tiny nitpick. I’m glad to see LTOS is still as rapid and snappy as ever. The Mjolnir is a breeze to use and navigate through, and I’m relieved to see Lotoo still nail the basics, even in a device this complex.

Navigation

Anyone who’s used a DAP in the past 10 years will find LTOS instantly intuitive. Of the options I listed earlier, my favorite way to look for my music has always been Album, and I always switch from list view to thumbnail view whenever I can. It’s easier to find pictures than words, and I love looking at my album covers in HD.

Unfortunately, just like their PAW DAPs, which I’ve critiqued for the very same issue in the past, Lotoo’s thumbnail view doesn’t look very good. Rather than having the album covers take up the screen like a collage, these thumbnails are spaced apart, surrounded by a gray bezel, and their bottom-thirds are obstructed by their respective titles, written in a font so large that they end up cut off anyway. I can’t comprehend why they’ve persisted with such an aesthetically displeasing menu when their peers have shown them the blueprint for almost a decade.

My suggestions to Lotoo are the same ones I’ve made since my LPGT review: Adopt a collage look, where the album covers are right next to each other. And, if you insist on having the titles there, make them smaller, laid over the cover with a translucent bezel. Something like this, perhaps:

I personally think that looks far better, and, most important of all, Lotoo have the ability to make these changes in a future firmware update.

In every viewing mode (Album, Song, Artist, etc.), there’s a button on the top right that allows you to tick a number of items and make a quick playlist out of them. An additional option only available in Song view is the ability to filter by file quality; High, Standard or Normal. One thing I don’t understand is why WAV is categorized under Standard. I think it belongs in High with the other lossless formats. You can also filter by sample rate, giving you the option to only show DSD files of a certain sample rate or redbook tracks of a certain sample rate range; say, from 48kHz to 192kHz.

Scrolling through any of these viewing modes is a breeze. Again, LTOS is quick and fluid, and you can scroll either slowly by simply swiping in the middle of the screen, or you can swipe at a far quicker rate by moving the cursor that appears on the right-hand side of the screen. The one thing I’m missing from the Android DAPs I’ve been using (particularly HiBy’s and Cayin’s) is the ability to scroll by alphabet:

So, when you’re quick-scrolling with that cursor, instead of arbitrarily skimming through the options, it’ll instead jump from alphabet to alphabet. I’d love to see such a feature, for the hundredth time, in a future update.

As previously alluded to, the Mjolnir features a dropdown menu, accessible by swiping down from the top, where you’ll find a number of shortcuts to functions, including:

1. Loop Mode (Shuffle, Single Repeat, Sequence or Loop)
2. Bluetooth
3. Volume Hold
4. Output Gain (Low, Middle, High and Super High)
5. XRC

Then, there’s a More Options button, where you can add more functions to the menu, including:

1. Sleep Timer
2. Show Lyrics
3. Breathe Light (referring to the volume wheel’s ‘breathing’ glow)
4. Digital Input (AES/EBU, Coax or Optical)
5. Digital Output  (AES/EBU or Coax/Optical)
6. Double-Click
7. Screen Flipping (to flip the orientation of the screen)

Double-Click refers to, like in the recent PAW DAPs, the ability to wake the screen simply by double-tapping on it. Typically, you can turn this feature on by going to Settings, but pressing Double-Click there does nothing. Instead, you have to go to the dropdown menu, go to More Options…, add the Double-Click button to the menu, then press it to toggle it on (as shown below). I hope Lotoo fix this issue in a future update.

On the bottom of the dropdown menu is a slider to adjust the brightness of the screen. And, on top is a Search bar, where you can search for albums, songs, files, etc. The only issue with the latter, which I’ve already brought up in previous reviews, is the Search History function. Rather than showing completed search attempts we’ve made in the past, it’ll instead log every single individual keypress we’ve made into the history. So, when searching for, say, Stevie Wonder, my recent searches will look like this:

S

ST

STE

STEV

…and so on. This is what it looks like when I try searching for Hello.

It’ll look even worse if I make a typo along the way. So, once again, I hope Lotoo can finally resolve this in a future update.

The only thing I haven’t mentioned is the Mjolnir’s one gesture-based command: Swipe up to return to the homepage. It doesn’t feature too many shortcuts beyond that. If I could suggest a couple, I’d say take a page out of Sony’s book and have a side menu, which’ll have links to other viewing menus and settings.

Now, in playback view, you’ll find all the usual suspects: The track’s cover art and track info, a progress bar you can freely slide below that, then playback controls at the very bottom.

Buttons Lotoo have added to this standard format include a Heart icon, which you can press to add the now-playing track to your Favourites playlist, a Loop Mode button and a Playing List button, where you can view all the tracks in the now-playing playlist. Then, you can tap on the album art to summon additional buttons on the top-right: An Add To Playlist and an EFX button. The latter lets you apply ATE filters and/or PMEQ presets on the fly.