{"id":27975,"date":"2021-05-15T17:15:59","date_gmt":"2021-05-15T15:15:59","guid":{"rendered":"https:\/\/www.hifi-advice.com\/blog\/?p=27975"},"modified":"2025-11-14T14:05:29","modified_gmt":"2025-11-14T12:05:29","slug":"grimm-mu1","status":"publish","type":"post","link":"https:\/\/www.hifi-advice.com\/blog\/review\/digital-reviews\/network-player-reviews\/grimm-mu1\/","title":{"rendered":"Grimm MU1"},"content":{"rendered":"

Review organized by Marc Loubeau \/ Prestige Audio Diffusion<\/a>
\nReview sample provided by Terrason<\/a>
\nInitial Review Sample Serial 13-0.002.016
\nSecond Review Sample Serial 13-0.003.037<\/h4>\n

Retail price including VAT:
\nNo internal storage: \u20ac9.800
\nAvailable SSD storage: 2 TB (\u20ac350) \/ 8 TB (\u20ac950)
\nOther storage sizes only on special request<\/h4>\n

After the Olive 04HD<\/a>, the AudioAanZee Ultra Flow<\/a>, Reference Flow<\/a>, and Reference Flow MkII<\/a>, the 432 EVO<\/a>, the Aurender S10<\/a> and N10<\/a>, the Pink Faun 2.16x<\/a>, the Meridian Sooloos MC200<\/a>, MD600<\/a>, MS600<\/a>, and 818<\/a>, the Melco N1A\/2<\/a> and N1ZH\/2<\/a>, the Euphony Buggy\/Zotac<\/a>, the Antipodes DX2<\/a>, DS<\/a>, EX<\/a>, CX<\/a>, and K50<\/a> Music Servers, and twice as many Streamers\/Network Players, not to mention various server software and playback applications that I have tried throughout the years, I figured that, by now, surely, there’d be no more large surprises for me. Well, of course, that’s when a new server entered my premises and totally surprised me.<\/p>\n

Grimm Audio<\/h3>\n

Founded in 2004 and based in Eindhoven, the Netherlands, Grimm Audio aims to use the collective forces of the greatest audio minds and to this day, all Grimm Audio products carry the joint insight of well-known scientists in the fields of audio electronics, acoustics, and physics.<\/p>\n

The two key figures are Eelco Grimm and Guido Tent, respectively Creative Director and Technical Director of Grimm Audio. Together with a team of software-, electrical-, and mechanical engineers, they produce audio equipment that is refreshingly different while yielding high praise the world over.<\/p>\n

Being Dutch myself, I can’t help but feel a little proud:-)<\/p>\n

MU1 Backdrop<\/h3>\n

Designed to complement the Grimm Audio LS1 loudspeaker system, the MU1 has sort of inadvertently taken the audio world by storm. This is in no small amount thanks to the efforts of Ben van Leliveld who was positively raving about the product on every occasion and during every demo that he hosted. Indeed, it was through one of Ben’s demos at the Listening Matters<\/a> showroom that I first laid eyes on the MU1, at that time combined with Zanden amplification and Kroma Audio loudspeakers. Later, I would hear the MU1 in the role envisioned by the design team, along with the LS1 speakers during one of the last demos at Garmt and Bjorn’s Beter Beeld & Geluid<\/a> showroom before it closed down. While I was quite impressed with the performance of the MU1+LS1 system performance, it was impossible to pin down how much of this was attributable to the MU1. Up until this point, I’ll be honest and admit that I thought it was mostly hype, possibly even more so when Ben proclaimed the MU1 to be The One server worthy to sell your CD player for.<\/p>\n

It wasn’t until a close friend and fellow audio reviewer obtained a MU1 for his review reference system that I really took notice. Like me, he had a hard time finding the ideal Music Server to work alongside his treasured CD player. We both feel that computer-based audio has made large strides but, somehow, still lags behind a good CD player in certain aspects. To be fair, if the CD player is of insufficient quality, it can also be the other way around, in many aspects, at least. Overall, though, there is something to CD playback that is less mechanical and stilted than any music server or streamer replay. Excuse me for not going into detail on this perception, as I’ve rambled on about this more than enough in my other Music Server reviews.<\/p>\n

Anyway, in his quest to find the ideal Music Server, the friend auditioned the best servers and streamers that are currently available and since I had already been doing the same thing for over a decade, we decided to join forces and compare the best of the best. I went over there with my Antipodes K50 and my accumulated knowledge and, well, let’s say that I was in for a surprise.<\/p>\n

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MU1 Description<\/h3>\n

With the MU1, the goal was to set a new benchmark in music player design, not only in terms of sophistication but also in terms of sound quality. Grimm Audio selected Roon for the user interface and the associated audio engine for file- and stream playback. An alternative User Interface and audio engine will be added later. Music can be sourced from streaming services such as Qobuz<\/a> and Tidal as well as from an external NAS or a USB thumb drive. Streaming from Qobuz sounds superb and in many cases identical to local playback. Local music can be added to an internal SSD that can be ordered in a 2TB or 8TB size.<\/p>\n

Powered by a twin-PCB switching power supply developed in-house to provide the lowest possible jitter values, the MU1’s core is shaped by a NUC board that runs Linux and the Roon Core server component. Importantly, Grimm does not just rely on standard Linux or Roon packages. Refusing to use standard libraries, the Grimm team wrote their own code from the ground up. This is where the MU1 differs from other music servers and likely an important reason for why it sounds so superb.<\/p>\n

Arguably, the actual<\/em> core of the MU1 is its custom-designed FPGA interface board. Whereas many competing products use standard oscillators for FPGAs, Grimm uses a very high-quality Tentlabs oscillator for this task while using an ultra-low jitter proprietary Grimm audio oscillator as the main audio clock. The Grimm clock and associated circuitry are encapsulated in a fully shielded box.<\/p>\n

It’s on this FPGA board where the MU1’s magic happens, with the FPGA interface accepting all file formats and sample rates from Roon in their native formats and converting them with a user-defined fixed multiplier (2x or 4x) using a “Pure Nyquist” decimation filter. The resulting signal is available on the rear via two AES\/EBU outputs and an RJ45 output that is dedicated to the LS1 speaker system. The MU1 can also be used to stream to other Roon endpoints but, naturally, this bypasses the FPGA board and its beneficial processing.<\/p>\n

The MU1 plays all the file formats that Roon supports, such as WAV and FLAC, and it has native support of PCM formats up to 8x the base rate (8FS or \u201cDXD\u201d) and of DSD formats up to DSD256. The FPGA processor will upsample 1FS and 2FS sources to 4FS and it will downsample 8FS and DSD or DXD formats to 4FS. In other words, there is no fixed sample rate and the used rate depends on the input rate. For instance, 44.1kHz will be output as 176.4, and 48kHz will be output as 192kHz while 96kHz will also be output as 192kHz. An input signal of 192kHz remains unchanged while higher sample rates will be downsampled.<\/p>\n

While I can understand there may be those who object to the notion of oversampling and insisting on retaining the purity of the original signal, it’s worth noting that the vast majority of CD players and DAC’s have a built-in oversampling that is usually 4FS. Even the earliest Philips players, including those with 14-bit DACs, used fourfold oversampling. With that out of the way, the downsampling<\/em> of very high sample rate source material might still sound strange but there’s a very simple explanation for this. It is the maximum rate that AES3 or S\/PDIF will support. The Grimm Audio team performed elaborate tests and has concluded that the clock accuracy (low jitter) is much more important for the audible results than an even higher PCM sample rate or even DSD.<\/p>\n

To make the magic of the FPGA board more widely available, the MU1 can also accept external inputs on AES\/EBU and S\/PDIF on cinch and TOSlink, and process these just like it does the internal Roon signal.<\/p>\n

<\/p>\n

Operation<\/h3>\n

The MU1’s most distinctive visual aspect is its large, gold-colored wheel on top which works in conjunction with the display on the front panel. Thankfully, the display is of the TFT sort and not OLED. Yes, the latter can have deeper colors and higher contrast, but I know that these displays burn in very quickly from experience. That’s actually why I leave the displays on my CH Precision equipment mostly off. With the MU1, however, there will never be any burn-in or other degradation and one can safely leave the display always switched on.<\/p>\n

\"\"<\/p>\n

While I love having a display and it shows an abundance of info, I noticed that the progress bar only remains in sync as long as you don’t manipulate the position within a track remotely.<\/p>\n

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As can be seen in the above photo, the two progress bars remain in sync so long as you don’t scroll within a track. If you do, the bar on the MU1 display will keep showing the old position as can be seen in the photo below. This resets when the next track starts to play and the two are in sync again.<\/p>\n

Eelco Grimm of Grimm Audio responded (translated and paraphrased):<\/p>\n

The problem with progress bar synchronicity has been identified and is fixed. It was introduced along with a Roon update that changed certain aspects of an extension that we use. The fix will be issued as part of the next user-installable software update. Along with this update, we will also add IR remote functionality to allow control of input selection and play\/pause. <\/em>Later this year, we will make the MU1 an official Roon endpoint which will negate the need for the extension and allow easier communication. Prev\/Next functionality is on the wishlist.<\/em><\/p>\n

(edit 11-09-2021: the new software is now released, v1.3.0, which enables remote control of play\/pause, previous, and next).<\/em><\/p>\n

\"\"<\/p>\n

Another small annoyance is with the gold wheel because there the software makes a distinction between a short and a long press.<\/p>\n

\"\"<\/p>\n

Much like the Linn CD12 that could be made to either skip to the next track or open its drawer depending on how long you pressed on it, which resulted in many inadvertent drawer openings, I have inadvertently switched off the MU1 many times when I actually wanted to return to the main screen. But at a certain point, you get the hang of it. And that’s when you realize that the rest of the implementation has actually been done cleverly.<\/p>\n

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By turning the main knob while holding it down the different sources are selected. If you \u2018hover\u2019 over a certain input for more than 1 second, it will be selected in preview mode which means that you can listen to the selected source at 10dB lower volume than the current setting to check if is what you like to listen to. When releasing the wheel the selected input is confirmed and the volume returns to the normal setting.<\/p>\n

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Menu page 3 allows the selection of 0, 2, or 4x Oversampling, the enabling or disabling of volume control, the format to use when outputting DSD data and the brightness of the front panel LED. Alas, even at its lowest, the LED is still quite a bit brighter than I would like. The fourth menu page shows the versions of the various internal components.<\/p>\n

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The final menu page is to enable the assistance\/support mode. It should only be activated when you have reported a problem with your MU1 and Grimm Audio support asked you to enter the unit into Assistance Mode. In this mode, a Grimm Audio engineer can get remote access to your device to help solve the\u00a0problem.<\/p>\n

\"\"<\/p>\n

The main display shows all the essential information such as Sample Rate and File Format, the currently set Volume in dB, the Mismatch volume in dB (for instance, as a result of normalization), Streamer Service, Artist, Song Title, Album name, Progress Bar, Track progress time, and Track length.<\/p>\n

In the normal playback mode, the wheel on top functions as a huge play\/pause button. I find that I actually use this function very frequently, because I swap sources a lot and because I like being able to control the music playback without always having to use the iPad.<\/p>\n

Of course, because it’s Roon, you can comfortably control the listening volume from the tablet or phone that you are controlling the unit with. With a fader on a screen, there’s always the danger of accidentally sliding it all the way over. To help mitigate this, you can set a hard limit within the Roon software. The Grimm team has taken this one step further by implementing a more intelligent safety limit on the volume control. Whenever you turn the MU1 volume control wheel or the Roon app volume fader quickly to the maximum position, the volume will jump back to the lowest level to protect from accidental operation.<\/p>\n

The MU1 combines seamlessly with the LS1 playback system. But, of course, the virtues of the MU1 can also be realized with DACs from other manufacturers and it’s the latter that I will write about in this review.<\/p>\n

<\/p>\n

Review Context<\/h3>\n

The MU1 will be listened to in combination with the CH Precision C1<\/a> DAC that connects via a CH Balanced Link XLR cable directly to the CH Precision A1.5<\/a> power amplifier that, in turn, drives Magico S1 Mk2 loudspeakers via Jorma Trinity<\/a> speaker cables. I will use the Antipodes K50<\/a> Music Server, the Aqua LinQ<\/a> with UPnP and HQPlayer NAA player boards, and various CD transports as comparative sources.<\/p>\n

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All power cables are Belden with Bals Schuko and Oyaide C-004 IEC connectors, interlinks are CH Precision Balanced Link and speaker cables are Jorma Trinity<\/a>.<\/p>\n

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Listening<\/h3>\n

According to Grimm Audio, Roon offers the best High-End user experience to date, and when it comes to the comfort of the user interface, I can only agree. In terms of sound, however, I have repeatedly found that Roon differs from alternatives such as UPnP\/DLNA, Squeezelite, HQPlayer, and MPD. In short, these aforementioned formats tend to sound tighter and more incisive than Roon (and arguably drier) while the latter tends to sound fuller and richer (and arguably less immediate and exciting).<\/p>\n

Roon had always sounded fuller to me than most other streaming- or music playback methods, but it was with the Aqua LinQ<\/a> network interface that I noticed these differences very clearly. And thereafter, I confirmed the relative differences with every other piece of hardware that I used. With this in mind, and given that I like my system to be as articulate as it can be, I was reticent to jump on board the MU1 experience. But little did I suspect that the MU1 was about to turn these experiences on their head!<\/p>\n

\"\"<\/p>\n

I started listening with the MU1’s 4x Oversampling engaged, as recommended. Later, I will also try the other modes.<\/p>\n

From the very first notes coming from the MU1, connected to the C1 DAC via a Jorma AES\/EBU cable, it was clear that the Grimm unit was superbly articulate and exhibiting none of the smoothing and rounding effects that I have gotten used to when using Roon in combination with other devices. Actually, without any comparisons, I’d already say that the MU1’s bass was really close to being as superbly incisive and defined as that of the Aqua LinQ. All I needed was half a song to know that it wasn’t just the bass – there was something fundamentally very right about the MU1’s overall performance.<\/p>\n

Being a bass fetishist, I wanted to settle the bass aspect first. In parallel with the MU1, I connected the LinQ to the C1 with the MU1 using another Jorma AES\/EBU cable and selected the UPnP input. This leads to the tightest, fastest, and most articulate delivery that I have so far been able to produce with the available equipment. Then, I compared it to the MU1 using a copy of the exact same recording and starting it simultaneously and then switching between the two devices. Well, I’ll be… this is an absolute first. Never before has a Roon source come even remotely close to sounding as a UPnP source, and certainly not in the bass. But after careful comparison, I can absolutely confirm that the MU1’s bass is every bit as incisive, articulate, fast, authoritative, and punchy as that of the LinQ.<\/p>\n

But it’s not just in the bass where the Grimm surprised me. Along with this superlative bass performance, comes a richer tonal saturation and a more organic fleshing out of projected images that lends more body and substance to vocals and instruments, adding realism and raising the emotional involvement. The LinQ remains beautifully neutral and in many facets, it is a match for the MU1 but in comparison, it now sounds tonally and dimensionally a little flatter and overall more matter of fact. What also makes the MU1 special is that it has more air and fluidity in the upper treble which further aids the emotional aspect.<\/p>\n

What’s more, its precision and transparency notwithstanding, the MU1 has a captivating sense of flow that I have thus far only heard from Antipodes servers. Granted, the K50, using its own AES\/EBU output sounds still smoother, fuller, and warmer, and with its supremely lush sound that washes over you completely unforced, it could be regarded as even more organic than the MU1. But the MU1 does dig considerably deeper in terms of articulation, low-level resolution, and ultimate finesse. With its higher precision, the MU1 is consistently more convincing while 100% avoiding sounding computer-esque or over-controlled.<\/p>\n

In terms of spaciousness, the K50 and the MU1 have similarities and differences. They both are just as capable of a room-filling sound in all directions but the difference is in the precision of imaging within the soundstage. Whereas the K50 unveils the layering as captured in recordings with no problems, the MU1 manages to portray them with more precision. It’s almost as if the software found a hidden focus dial that was somehow left in the middle position and now turned it all the way up.<\/p>\n

Adding the LinQ to the mix using HQPlayer on the K50 with Roon, the combination gains articulation and tightness compared to the K50 used on its own but it also loses a portion of the server’s organic and lush quality in the process. And, remarkably, the MU1 still beats the combo in terms of speed, articulation, and precision. How I love the MU1’s way with transients – they’re lightning fast! But never ever are they over-etched and there’s never a feeling of hardness or sharpness. There’s nothing that stands in the way of the musical performance. Rather, everything is balanced just so that the audiophile mind agrees while the soul latches on.<\/p>\n

Sonically, the MU1 leaves nothing to be desired. Functionally, it offers fewer options in terms of streaming- and playback methods than the K50 and also has fewer output options. Whereas the Antipodes is something of a Swiss Army Knife by offering a multitude of server- and streamer software options that output as AES\/EBU, S\/PDIF on coax, S\/PDIF on BNC, I2S, and USB, the MU1 is currently limited to Roon only and offers only AES\/EBU outputs. But whether or not this matters will depend on the intended use. And especially since Roon has been implemented such that it sounds in line with the best formats, why should one want to go beyond Roon?<\/p>\n

I certainly would not have expected it after raving about the K50 relatively recently, but the MU1 has impressed me deeply. It may not offer all of the big Antipodes server’s functionality, but sonically, it takes what the K50 does, which is to sound like music, not clinical computer replay, while further adding to it to provide the best I’ve heard yet from a Music Server!<\/p>\n

<\/p>\n

Sell your CD player?<\/h3>\n

Now, to get back to Ben’s claim that the MU1 is worth selling your CD player for. Is it? For the most part, yes, indeed. The MU1’s performance is so superb that it’s a no-brainer. That said, if I’m honest, I must admit that even the MU1 does not sound entirely<\/em> identical to the best CD transport that I have available. The MU1 certainly performs equally as well in the familiar audiophile parameters such as transparency, refinement, speed, dynamics, or even resolution. Actually, many CD transports will struggle to scrape the amounts of detail off the disc that the MU1 is capable of. But what CD, when done right, can still add is more depth and flow. But fair is fair, the difference has become smaller than with any server that I heard before.<\/p>\n

All this left me wondering how the Grimm team managed to combine all these traits in a single device. I asked and the answer was, somewhat evasively, “you have to know what to measure for”. Personally, I think it has a lot to do with the FPGA board and the Grimm Audio clock, as well as the power supply. Inside is a custom-made switching power supply and although the principle is far from unique, it takes deep knowledge to make one that performs superbly while not contaminating its host or other components in the system with noise. Evidently, the Grimm Audio team has taken great care in designing and implementing this part.<\/p>\n

Oversampling<\/h3>\n

The MU1 can be set to Original, 2x, and 4x. The differences are easy to hear and I had a clear preference for the highest setting. Original provides a “squarer”, more “normal”, relatively direct-coupled, and earthy sound that I find attractive for its superb bass precision. But along with the earthiness comes a dulling in the high frequencies and a much more compact soundstage.\u00a0 Actually, compared to other digital sources, it’s fair to say that the MU1 with 4x Oversampling provides more air than is strictly neutral. But along with this also comes its organic quality, the extra refinement, and the deeper and wider imaging that sets the MU1 apart from most other servers. More importantly, I find that it most resembles CD playback when set to 4x Oversampling. And most importantly, the airier presentation is provided without the treble sounding tipped up in any way.<\/p>\n

The 2x setting lands precisely in between the two other settings with enhanced refinement and fluidity with a moderate amount of smoothness compared to the Original setting (no Oversampling) but less lush and refined and spacious than with the 4x setting.<\/p>\n

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Mola-Mola Tambaqui<\/h3>\n

Simultaneous with the MU1, I also had the Mola-Mola Tambaqui DAC<\/a> on review. As this DAC has its own review I won’t go into specifics here, but suffice to say that this unassuming little DAC is something special! Not only does it sound superb, but it also pairs very well with the MU1.<\/p>\n

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Inputs<\/h3>\n

When routing well-known digital sources through the MU1, they receive the same benefits as described in the Oversampling section above. While that can have a desirable result, I also found that some of the original component’s character was diminished when routed through the MU1. For instance, when connecting three sources with very different sonic characters such as the Zanden 2000 CD transport, the Aqua LinQ network transport, or a Spectral SDR3000 CD transport, their relative differences were lessened and smoothed, and mixed with the Grimm benefits. Meanwhile, none of the sources sounded as superb as the internal Roon server. Thus, the decision to use the external inputs will be a personal one.<\/p>\n

S\/PDIF output<\/h3>\n

After I finished writing this review, Grimm issued the news that they will add a cinch S\/PDIF output to all MU1 units, in addition to the pair of AES\/EBU outputs that it currently has. Alas, this change cannot be retrofitted to older models.<\/p>\n

Update June 21, 2021 – Updated MU1 hardware<\/h3>\n

While the Grimm Audio team worked on implementing the S\/PDIF upgrade, Bert Bazuin of Terrason Audio<\/a>, the Dutch distributor for Grimm, kindly agreed to let me keep the series 002 demo unit for a while to enable further comparisons. Last week, Bert called me up to let me know that the work on the new model was complete and the unit was now available. And sure enough, a couple of days ago, a box arrived with in it a brand-new series 003 MU1 unit for me to assess. The reason for this extra comparison is that along with the S\/PDIF hardware update, Grimm has also tweaked some of the internal hardware and has found ways to further reduce the jitter as measured in various locations, even if it was already extremely low.<\/p>\n

Although the S\/PDIF output is physically available on my sample, it is not yet enabled in the software. This will follow later as part of a software update.<\/p>\n

Comparing the two units side by side (using two Roon accounts) with the CH C1 DAC and two Jorma AES\/EBU cables, to my surprise, the new series 003 unit does indeed have an even denser, more direct,\u00a0 and more impactful delivery. Remarkably, even though the initial series 002 review model was already benchmark-setting in terms of bass quality and dynamic impact, the new model simply has an even more robust sound!<\/p>\n

The bass now has an impressive “chiseled-from-granite” quality while the midrange has an even more energetic, direct, and propulsive feel which combines to an even more visceral and communicative delivery with an even higher jump factor. For me and with my system, this translates to an even more robust and engagingly “live” sound than with the earlier model or any of my other server\/streamer solutions.<\/p>\n

On a relative note, with this change, the MU1 has shifted its presentation away from gently smooth and organic to what I regard as a cleaner, more direct, and more exciting delivery while retaining the musicality and still involving me emotionally. Depending on the individual’s views, however, it can be argued that this change has also made the MU1 sound relatively drier and lose some of its warmth and flow.<\/p>\n

Altered character and personal preferences aside, after having compared the two versions for days on end, the updated series 003 MU1 frequently had me excited. But I also cannot fault the earlier model’s interpretation. Bottom line, both servers perform absolutely magnificently in their own right and I could very happily live with either.<\/p>\n

Owners of older MU1’s should definitely not feel short-changed by missing out on this latest update, but all the same, people contemplating getting a MU1 now should feel confident that they are getting the best the firm has to offer.<\/p>\n

Needless to say, in either version, Highly Recommended!<\/p>\n

Update 11-09-2021 – Remote Control Functionality<\/h3>\n

Grimm is working on IR remote control functionality that enables switching inputs as well as transport functions such as play\/pause, previous, and next.<\/p>\n

\"\"<\/p>\n

Software version 1.3.0 has now been released, which adds IR remote control functionality. However, there are no further instructions, so I took it upon myself to try and make this work. As I found, the MU1 unit does not contain an IR receiver, so you’ll have to add this in the shape of an external “eye” with a cable that connects to the MU1’s back, like the one shown below.<\/p>\n

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Link to item on Bol.com<\/a><\/p>\n

Then, it’s a matter of choosing the desired function on the MU1 on the IR setup page, pointing any remote control handset to the receiver, and pressing the desired button. Repeat for all the required functions.<\/p>\n

For detailed instructions, see the MU1 tips & tricks video<\/a> on the HFA YouTube channel<\/a>.<\/p>\n

Update 19-10-2021<\/h3>\n

Grimm Audio has officially announced the new software that enables IR Remote Control, as well as the S\/PDIF output, apparently. I have just tested this and indeed, it works in parallel with the AES\/EBU outputs, and without having to make any settings. Please find all the official information below.<\/p>\n

We are pleased to let you know that new firmware for the MU1 is released. Version v1.3 adds two features that were in strong demand: an S\/PDIF output and IR control.\u00a0The RCA S\/PDIF output that can be found on the latest batch of MU1 hardware is enabled. Customers can now use their favorite RCA S\/PDIF cable.\u00a0<\/em><\/p>\n

The other feature also enables a MU1 hardware connector: the 3.5mm \u2018remote control\u2019 jack on the back, designed for use with common infrared extenders. IR remotes now offer access to play\/pause, volume, source selection, previous\/next track, and in\/out standby. Our team took this assignment serious and the MU1 can therefore be used with any type of IR remote handset on the market. In case you find a remote that does not work, please let us know.<\/em><\/p>\n

The MU1 software manual<\/a> provides instructions for programming the IR function. For a good impression, watch the nice YouTube\u00a0video<\/a>\u00a0that MU1 customer and\u00a0Hifi-Advice<\/a>\u00a0author Christiaan Punter made. Enjoy!<\/em><\/p>\n

Conclusion<\/h2>\n

The beauty of the MU1’s sonic presentation is that it is tight, precise, articulate, and very highly resolving, whilst simultaneously avoiding sounding dry or clinical. On the contrary, the MU1 has a timbrally rich tonality and superb fluidity with a tiny hint of smoothness but without any dilution or smear. Additionally, the MU1 has a captivating\u00a0 3D portrayal and sense of flow, along with the kind of organic presentation that makes it not only a very accurate Music Server but a highly involving, emotion-inducing Music Machine.<\/p>\n

Update 05-05-2024<\/h3>\n

About one year after I finished this review, Grimm released a big firmware update that improved the Oversampling filter behavior. This altered the server’s characteristics, not just when using the 2x or 4x settings, but also when using the “No oversampling” setting. This update had a significant impact, enhancing refinement, delicacy, transparency, and precision. For the most part, I felt this was an improvement, although it did mildly reduce the player’s overall liveliness and expression. Grimm released further smaller updates that introduced helpful new features without changing the sound.<\/p>\n

The initial firmware update ties in with Roon’s ongoing sound quality changes. Over the years, Roon has reduced the intervals at which they release new builds to what feels like an update every month. When I initially reviewed the MU1, I was hugely impressed that it seemed impervious to the Roon characteristics. To my surprise, it did not suffer from the excessive warmth and thickness through the upper bass and lower midrange, which was so familiar to me from all other Roon servers.<\/p>\n

The introduction of Roon build 2.0 also introduced the aspects typical of Roon for the MU1. Throughout the successive Roon updates, the presentation has also become more variable. With some Roon builds, the server sounds really great, and with others, not so much. It is the same with any other Roon server, and Grimm is not to blame, although the aforementioned change in the MU1’s filtering does emphasize the differences.<\/p>\n

Whereas the MU1 used to be my crispest, liveliest, and most expressive source, it is now superseded by UPnP\/MPD in these areas. The CD transport, which used to sound mellower than the MU1, now sounds livelier and crisper. Perhaps most telling of all, my DAC is Roon Ready, and the MU1 can stream directly to it. Naturally, I tried that as part of this review, only to find that the Grimm sounded much better to me using its AES\/EBU output. However, that situation is now reversed. The other side of this is that those who may have initially felt the MU1 to be a little too clean or too dry for their tastes will likely feel differently now. To those, I recommend giving the MU1 another chance.<\/p>\n

In summary, the MU1’s sonic balance has changed since I first reviewed it due to firmware updates and ongoing Roon updates, which means that it now requires different tuning.<\/p>\n

Aspects that I now pay special attention to to achieve the original MU1 performance (as described in this review) as much as possible include using fast and open-sounding solid-core power cables with very low inductance, open and expressive-sounding digital interlinks, placing the server on Ansuz Darkz T2 footers (other direct-coupling footers can also work well), connecting only a single Roon server to the network at a time (or stopping the Roon core on the second server, as a second Roon core will increase the blurring effect), disabling and removing all DSP\/MUSE filters in Roon, using a crisp and articulate-sounding network switch (avoiding those that sound ethereal and dreamy), and disconnecting any unneeded components from the network and power supply.<\/p>\n

This addendum has been added to provide up-to-date information, enabling prospective buyers to make a fully informed decision.<\/p>\n

Importantly, even though it has changed, the MU1 remains my favorite server.<\/p>\n

\"\"<\/p>\n

Associated Equipment<\/a><\/p>\n

<\/h3>\n

Videos on the Hifi-Advice YouTube Channel<\/h3>\n

How to add Remote Control Functionality to MU1<\/a>
\nHow Sooloos became Roon<\/a>
\nGrimm MU1 and Antipodes K50<\/a>
\nHFA Front Page<\/a><\/p>\n

Try out Roon for yourself<\/h3>\n

Get Roon 1 month for free<\/a><\/p>\n

External Links<\/h3>\n

Manufacturer: Grimm Audio<\/a>
\nDistributor for the Benelux: Terrason Audio<\/a><\/p>\n

Distributor for France: Prestige-audio-diffusion<\/a>
\nContact: Marc Loubeau
\nTel\u00a0: +33(0)6 49 89 68 88
\nEmail\u00a0:\u00a0contact@prestigeaudio-diffusion.fr<\/a>
\nWebsite: www.prestigeaudio-diffusion.fr<\/a><\/p>\n

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