MU2 direct to power amp
So far, I’ve ignored one of the MU2’s alluring functions: relay-based analog volume control! The volume control is always in the signal path, but when set at 0.0, it is at a unity position and “effectively” bypassed, and that’s how I used it for its overall assessments.
Its volume control allows the MU2 to be connected directly to active loudspeakers or a power amplifier, bypassing an external preamp. When using the MU2 like this, I will bypass the CH Precision L1 preamp, directly connecting the Driade Flow Link Reference 808 XLR cables to the CH Precision A1.5 power amp.
By default, the MU2’s large rotary dial on top controls the volume level whilst briefly pushing it engages play/pause, and a long press enters the menu. Depending on the chosen menu item, it can control a host of other functions. The easiest way to control the volume, however, is via Roon or the Grimm web interface, which can be opened on any device that runs a web browser. The web interface also allows switching of inputs, along with various other settings.
For starters, the MU2’s preamp section is ultra-quiet. While the relays make a soft mechanical click when changing the volume and no music is playing, nothing can be heard from the speakers. Just dead-silence. And when playing music, it is the same; just the changes in level, nothing else.
I already caught a glimpse of the preamp’s neutrality when using the volume to align the MU2’s output level with other DACs, but now that I am actively using it, it is abundantly clear. The preamp stage and volume control are, quite simply, unvoiced and utterly transparent.
The L1 preamp, by comparison, adds a dose of charm, spaciousness, liquidity, and flow while remaining linear and neutral. At a hefty price, I should add. But if it is purity that you are after first and foremost, then there are real benefits to skipping an external preamp altogether. Even one as sophisticated as the L1.
When directly connected to the power amp, the MU2 produces even tighter and more controlled bass whilst remaining relatively fluid and refined. It doesn’t become brittle or dry as some DACs can get when connected to a power amp directly, but without the L1, it does sound quite matter-of-fact and sober. When using the MU2 like this, I recommend trying different interlinks and power cables.
I’ll leave it in the middle whether the L1 adds romance or the MU2 subtracts it, but all by itself, the latter certainly relays the information in the source with no beautification. Brutally honest? I would not go that far. Certainly not when carefully matched with synergistic cables. Although the MU2 does sound more analytical without the CH preamp, I really cannot say it is brutal because it always remains refined and polite and refuses to get rough or aggressive. With the MU2 connected directly to the power amp, there is simply no “tube-like” charm or richness, additional expansiveness, or beefed-up bass. You get what’s in the source, no more and no less.
Footers
Under the MU2, I tried StillPoints Ultra SS and three versions of Ansuz Darkz. Interestingly, the MU2 seems less sensitive to the influence of footers. Therefore, I assessed the unit primarily with its own neoprene-layered feet directly on the Artesania KSH2 Krion shelf or the HRS EXR Audio Stand.
When adding either of the aforementioned footers, the MU2 responds as expected, and when the budget stretches, it’s worth investigating to maximize the performance, but the MU2 sounds very well-balanced on its own. Nevertheless, I found that the StillPoints worked very well at maximizing the MU2’s robustness and spriteliness, and the Ansuz T2S worked particularly well at injecting an extra portion of magic into the sound while gently enhancing the articulation and precision.
Interlinks
I keep returning to the Driade Flow Link Reference 808 interlinks for their linearity, transparency, and character-less neutrality. I value these qualities in a cable, not just for reviewing purposes but also for my personal musical enjoyment. With the MU2, too, these cables work fabulously well. If you do not wish to alter the server’s inherent character but play to its strengths, I can wholeheartedly recommend them. That said, not everyone has the same preferences, room acoustics have a massive influence, and system synergy is a very important aspect. And that’s where different cables come in.
The Vermouth Statement interlinks are a great choice to add a nice dose of creamy smoothness and romance to the sound while retaining the resolution and refinement. These cables work particularly well when the MU2 is directly connected to the power amp.
The Mad Scientist Black Magic Gold provides almost the inverse of the Vermouth and is not quite as refined, fluid, or airy, but they positively maximize the robustness, slam, dynamic contrast, and crispness of texture, leading to a very realistic rendition, especially when playing vocal music or music with real acoustic instruments.
Power Cables
The power cable that I used for setting the baseline for this review is a simple Belden 19364 with a Bals Schuko and Oyaide C-004 IEC connector. Naturally, there are better cables out there, but it is trustworthy with a very even-handed set of skills. It’s quite neutral and linear and neither overly tight nor overly smooth.
I tried a few other power cables and found that the GigaWatt LC-2 EVO does a great job at enhancing the tightness, articulation, and midrange clarity whilst remaining commendably neutral. This cable works very well, provided one does not expect it to add any romance.
The GigaWatt PowerSync ULTRA provides bigger and fuller bass with more body and deeper tonal saturation, along with a subtle dose of lushness and a wider projection of ambient sounds while avoiding sounding warm. Between the two GigaWatt cables, I think the PowerSync ULTRA works best for most situations, especially when the MU2 is used directly to a power amp.
The Oyaide Tunami V2 with 029 connectors also made an interesting match, providing a ballsy and powerful delivery combined with a delicate touch of fluidity and warmth.
The Mad Scientist Black Magic Ultra, finally, provided agility and airiness with great flow and a touch of magic.
With all these different perspectives, making a single recommendation is difficult. Ultimately, of course, the best cable for a given system will be the one that plays most synergistically in that particular system and caters to the user’s specific needs. In any case, I found it interesting to find that the MU2 responds eagerly to power cables.
Conclusion
In many ways, the MU2’s DAC section picks up and continues in the exact same vein as its server/streamer part. Like the MU1, the MU2 sounds neutral yet natural, fast and articulate yet fluid, and accurate without sounding tonally lean. Strikingly, it presents as warm without actually sounding warm. No matter what you play, there is never any harshness, edginess, or even remotely stereotypical digital about it. It’s got fluidity, grace, and charm, and its pacing is spot on, always toe-tapping and neither hurried nor slow.
The MU2 invites long listening sessions and performs its task almost anonymously, leaving the music to do its thing. Whether used with an external preamp or connected directly to the power amp, the server has a tightly controlled and precise yet calm and composed delivery with a velvety and laidback quality in the midrange, making for an intricately detailed yet highly sophisticated performance.
Try out Roon for yourself
External Links
Manufacturer: Grimm Audio
Distributor for the Benelux: Terrason Audio
Thank you very much for this review. You continue to be, IMHO, the best audio server reviewer, able to understand and communicate the nuances of these machines, which much more difficult than it seems.
The comments of interconnects and power cables were interesting thanks.
Did the MU2 earn your recomendation?
Great review Christiaan, Question for you. Have you looked at the HiFirRose products? Specifically the 150B and the 130. I am considering the 150B. Matching it with a Bryston 4bsst, Mark Levinson 280S, balanced Cardas cables through out and a Arcam FMJ old school CD player with the Dcs ring dac vintage 2003. Love the sound looking g to progress. My sound is to my ears still excellent..obviously looking to improve however, the all in one unit goes against my audiophile instinct..Your thoughts are very much appreciated
I know of HifiRose but have yet to hear one in my system.
Thanks for the review. I have the Grimm MU1/LS1be/SB1 system. Unsurprisingly, many of your observations correspond to what I hear. It’s the first time since my KLH stereo from college days that the whole system is from 1 manufacturer. And it is quite an accomplishment.
I did read your review actually a few times,.
I have MU2 on order,.
Was surprised Not to see your endorsement for this product.
At Axpona I had dealer switching between Mola Mola T and MU2 . ( he had both connected to rh preamp ) , I could hear a slight difference between the DACs , MMT did sound like it had more authority and was but brighter .
Hope I like the sound of MU2 in my system ( Martin Logan 15a powered by Luxman M900 and MU2 ( hopefully soon )
Hi David,
Between the MU1 with Tambaqui DAC and the integrated MU2, it is a matter of convenience, value, and personal preference. The MU1 allows the user all the freedom to choose a DAC that works synergystically with the system or caters to particular listening preferences. The M2 ticks many boxes and is very cost effective considering it has not only a server and DAC, but also a preamp on board.
As balanced and objective as I try to be with my reviews, they still reflect my personal taste and that, together with the cost/performance ratio and various other factors, defines a component getting a reward or not. What I found was that the MU2’s sonic presentation deviates from the course set by the MU1, meaning that if one loves the MU1 with a given DAC, the MU2 may steer things in another direction. It is a different product, not an automatic guaranteed upgrade. As such, I personally prefer the MU1 and its digital output that allows freedom of DAC selection, and this is reflected in the review.
With all that said, I stand by what I wrote in the review and in the end, a home audition will provide definitive answers. Do let me know the results of your listening session!
Thank you , out of all MU2 reviews I found your most in depth and informative.
I’m patiently waiting for my unit to come.
Might be taken seriously when it supports Spotify Connect. Otherwise it’s misreading its already-niche “audiophile” audience. Aurender, Auralic, Lumin all support Spotify Connect.
Agreed: having more options for streaming services is always better. It’s nice to be able to choose. I use Qobuz and am very pleased with the sound quality but Spotify uses a lossy format at 320kbs, not an audiophile source, and therefore, I don’t feel it is a serious omission.
Spotify is NOT a lossy format as it’s 320kbps vorbis, not mp3 as is often misleading mistaken. Even audiophile ears would struggle to hear the diff between FLAC and Vorbis at 320kbps.
As far as I know, Vorbis is a lossy format. In any case, I’ve not yet heard Spotify sound as good as Qobuz or Tidal.
All digital formats are essentially lossy and the difference is made from LAN connection, power supply, of course the hardware of the streamer and DAC. I suspect if they get Spotify into MU3, or into MU2 via firmware, you’ll find Spotify’s MUCH larger library will sound just as good. Tidal is now around 96% of the library (but UX still sucks) and Qobuz is for very limited tastes with 40% of Spotify’s global library. Stats from Spundiiz with my own playlists — around 120,000 songs of many genres.
I carefully read your review of the MU2. This week I went to a friend who had the MU 2 in his system. He is an experienced audiophile. It has a large hall built high up. He told me that he had never heard a dac sound so good. He uses the MU2 with his pre-amp. I also liked it.
I have the INNUOS STATEMENT, with the APL DSD-SR-SE dac. How would you compare these two DAC-STREAMERs? What are their characteristics in relation to each other? Do you have a preference? You have already published an article on APL’s DSD-AR.
Thank you so much
Tough to compare and extrapolate off the top of my head, and with a server that I have never heard in a controlled environment, let alone compared to other servers. I’d be inclined to think the two may be comparable in quality although there will undoubtedly be differences. These will be of personal preference. I recommend trying it for yourself.
Goedendag
Kunt u mij een advies geven over het volgende.
Ik speel nu met een soulution 711 via een sotm ultra streamer op een msb analog dac met (goede) analoge volume regeling module op magico Q3.
De bediening van de sotm via ipeng is erg complex. Ik heb derhalve een Roon licentie genomen en dit rechtstreeks aangesloten via de V2 renderer module opi de dac. Het geluid is sindsdien erg vlak/saai geworden waardoor ik op zoek ben naar een alternatief. Ik overweeg een mu2 van Grimm maar heb twijfels of het niet beter is om bv een aurender of mu 1 te combineren met de analog dac en t.z.t. een aparte voorversterker vb een soulution 725 of ch Precision te gebruiken. Deze laatste optie lijkt me muzikaal gezien de beste echter prijzig of zou een mu2 ook deze kwaliteit geven
Mvg Ruud Warringa
Hi Ruud, as you found, Roon has a different sound than MPD and UPnP, and depending on your system and preferences, one can be preferred over the other by a significant margin. To me, Roon sounds smooth, rich, and fluid, but it is not the last word in speed, articulation, transient sharpness, and expression. However, I would not refer to Roon as “flat” so maybe there’s another culprit or something that can be done to offset the change and restore the balance. If you like the SOtM, then another remote app might be a solution. You could try Rigelian, or search for other MPD-compatible apps. Aurender also works with MPD, and their app is an adaptation of the mpad app. Between MU1 + DAC versus MU2, the latter achieves a very high quality and is cost-effective, but the former offers more freedom to choose a DAC according to your desired voicing. The preamp section of the MU2 is very transparent but no true alternative for a CH L1 or Soulution 725.
Roon’s character is audible on every server, so, if you prefer UPnP, then I recommend finding another solution. Aurender works with MPD which is typically easy to operate, and has the potential to sound close to UPnP. However, the implementation has a large impact, and I would be hard-pressed to choose between an Aurender and the MU 1 or MU2.
Hi Christiaan,
Can you please tell me who made the acoustic pannels (two grey looking blocks) you have on the front all?
Thanks.
They are Sirrahs, made by R.T.F.S. See my review.
PS: each of my reviews has an Associated Equipment link at the bottom, as well as a link to the particular composition of the system at the time of the review.
Hi Christiaan
I’m currently debating over whether to buy the MU1 or MU2. Following your review, a few questions:
1. Is the MU2 in server/streamer mode perhaps a tad politer than the MU1?
2. If a user was after an existing, toe-tapping sound, which DAC would you recommend be paired with the MU1?
3. With regards Roon, I too share your assessment of it but hasn’t Grimm worked with Roon to mitigate the software’s somewhat softer, recessed sound signature?
Any feedback gratefully received.
And thanks for all your articles and insights. I often read your site.
Hi John, thanks for the feedback, nice to hear you like my work! Although it is hard to compare a server with built-in DAC to a server with an external DAC of choice, I would indeed say the MU2 leans to the polite side. It is suggested that Grimm “worked with Roon to mitigate the software’s somewhat softer, recessed sound signature”, but I don’t believe they have tuned the server in any way. They strive for a neutral-sounding and correct-measuring performance. Nevertheless, when I first reviewed the MU1, I had a hunch that the server’s balance of hardware and software compensated for Roon’s signature, as the MU1 was the liveliest Roon server I heard, bettering even my best UPnP endpoint at that time. A few updates later, however, the MU1 sounds more refined, airier, lusher, and indeed also relatively more polite. The MU2 is brilliant in providing superb resolution in a fluid and “analog” manner, but if you want the freedom to tune the sound to your liking, the MU1 may be a better choice. Two great DACs for the MU1 are the Aqua Formula xHD and Mola Mola Tambaqui. Other DAC brands that sound exciting and toe-tapping that spring to mind are Denafrips, Laiv, COS, and dCS. The best DACs I heard, price no object, are Playback Designs and CH Precision.
Thank you. While the MU1 provides some tuning flexibility (with a separate DAC), I may now look at alternative servers/streamers that don’t rely solely on Roon (despite the recent update that claimed to improve SQ). The LinQ is one. And thanks for the DAC recommendations. The Laiv is an interesting option: some reviews say it’s laid-back and warm, others say it’s exciting and energetic. Maybe it’s both.
Hi John, FWIW, I would describe the Laiv Harmony DAC as neither warm nor laidback. Ultimately, your own ears should be the judge:-)