The Grimm MU1 Review. The Magic Audiophile Streamer.

The Grimm MU1 Review. Digital Nirvana.

By Steve Huff

Over the last few months I have been able to listen to some amazing pieces of gear in the ever growing world of HiFi. I sent two pieces back without review this month (they buzzed, hummed out of the box). Today I am going to write about a piece that I feel will be very hard to write about due to what it is, what it does and what it cost.

Up front I will state that The Grimm MU1 Music Streamer and Server is another one of those rare “special” pieces that sit amongst the most pleasing I have experienced in HiFi. In fact, this piece joins the ranks of my Fleetwood Deville SQ speakers, the Enelum AMP 23-R and Weiss DAC 501 that I have purchased for myself.

As special as it is, I was not so sure I wanted to review the Mu1 initially.

Why? Well, at first glance it seems overpriced for what it is. This is a $10,500 Streamer/Server and that price is without an internal SSD drive included. No DAC is included here and that will also be needed for this to work within your system and make beautiful music.

We can get a music streamer for a couple hundred dollars. We can buy really nice ones made for audiophiles for around $2k and up. Heck, my last streamer lasted me two years and cost me $1800. That was my Lumin U1 mini and it did a great job of sending those digital bits to my DAC. In fact many feel all streamers are the same and make zero changes to the sound. I used to think streamers made a small difference, but not one big enough to warrant a five figure price tag.

So the Grimm MU1 was a learning experience for me as well as I learned what I used to think was not quite right.

So if my last streamer did a great job and cost me $1,800.00 then why would I ever consider a streamer that sells for over $10,000? Yea, exactly. That was my dilemma. Even so, the more I listened to my system with the Grimm MU1 installed, the more I understood “The Why”.

In fact, I have never heard digital music sound quite like this, and I have heard some pretty snazzy setups that cost much more than the Grimm does. In fact, the more I listened and the longer it stayed, the more I was trying to talk myself out of buying one for my system!

I have learned one thing for sure and this is that the Grimm makes a real and very true “Holy Wow” kind of change to my digital music enjoyment. It’s not a shocking night and day thing initially but it is one of those pieces that you appreciate more and more over time. If you take it out of your system after a few weeks or months of using it, YOU WILL NOTICE it is gone! YOU WILL miss it!

So why is this the case? Well, it’s all about the clock and the scaling that is done through the AES and S/PDIF output. Yes, with this unit one must use the AES or S/PDIF output only as this is where this machine weaves its magic. I will note that my review unit was made before S/PDIF was implemented with the scaling. So I will be using the AES output with a Cardas AES cable on this unit going into various DACs.

So out of the gate this is not your every day streamer as it will actually upsample/upscale the music before it hits your DAC. I have actually found that this streamer dramatically improves the sound of any DAC hooked up to that AES output as well. This means you may not need a crazy high end DAC to appreciate what the Grimm is doing. The better the DAC the better the sound of course  but the Grimm is doing some of the work that DACs normally do.

This in turn makes the DAC have to work less as the Grimm is doing more of the heavy lifting here. This may be why.

The MU1 is FOR ROON USERS ONLY! 

The Grimm MU1 is a music streamer/server made only for those who use ROON and for those who want a streamer that is as good as it gets in mid 2022 for sound quality. It’s for the audiophile, the perfectionist. For those who crave that last 15% of performance from their system. Let’s face it, no one else is going to plunk down this kind of cash on a streamer/server besides those of us entrenched deep into this audio hobby/passion of ours.

If you do not know what ROON is, you can check it out HERE. Basically it is a music management system that allows all of your music to be indexed and organized in a very nice and graphical way. It allows us to stream from Tidal or Qobuz as well. There’s a lot to it, but many consider it the best music software on the market. I love ROON and have been a user for years.

For me ROON is the best all around music management system and a great way to discover new music and stream Qobuz or Tidal. It’s solid. Rock solid. It’s the one music management and discovery app/software/hardware that is adored by thousands of music lovers all over the world.

The Grimm unit (or Roon) doesn’t do Spotify at all though, and therefore you can not stream Spotify to the Grimm. I feel this is a con, at least for me, because yes, even Spotify can sound deliciously good with the right gear. I do see on the Grimm website for the MU1 that Spotify Connect is coming soon and I did confirm this with Grimm. One thing is for sure, updates are always being worked on it seems as the MU1 has had quite a few updates already. These updates happen direct from the unit itself (when hooked up to your network).

As for ROON, while not everyone has a ROON subscription, this is the first device I have ever used that makes a very strong case for getting one and enjoying all it has to offer.

Not only does this streamer change the game when it cones to the sound quality coming from my system (and ROON itself which can be lackluster in sound with some gear) it is hands down the easiest way to get setup with ROON that I have ever experienced. In fact, this streamer is so easy to set up and use and I love it for this reason alone.

But ease of use and setup alone is not a reason to spend five figures on a music streamer. No, this must have it all for these ears and wallet.

If I were to spend this kind of cash on just a streamer it would have to have certain qualities. 

It must look good (The Grimm looks beautiful)

It must be made well (it is)

It must be glitch free (so far so good)

It must be easy to setup (it is, very)

It must sound amazing (this streamer is different from the rest in sound)

It must come from a passionate designer and company (The MU1 was created by Eelco Grimm and Guido Tent and the rest of their passionate team)

I asked myself…CAN A STREAMER REALLY BE A GAME CHANGER within a System? 

There is no app for this streamer or a way to control it other than the ROON software and the big brass looking dial up on top of the Mu1. But that is cool to me as ROON is as good as it gets for software and app control.

The MU1 is unlike other streamers on the market today and can only be compared to something like the Innuos Statement Streamer, which is $13,500 and also does not include a DAC. Then there are others that go into the $50k price range. When you look at these pieces then the Grimm doesn’t look so ridiculously priced, especially when users and owners are claiming the Grimm can and in some cases does best the rest.

The Inside doesn’t look too Fancy

The Grimm MU1 streamer uses an off the shelf NUC inside with an i3 processor (Basically a small form factor mini PC) . In fact, the inside of the Grimm doesn’t scream “This is a $11k streamer to me” at all. But the magic of the Grimm does not lie in the NUC.

Rather it lies in the CLOCK and the AES/S/PDIF output, which as stated earlier is the only output you want to use on the Grimm.

It is this output that brings the magic, the analog like sound and the rich deep reproduction of the music that brings on the major goosebumps. It is this output that brings the magic and the price tag to this HiFi music streamer and server.

There is also a customized FPGA board made by Grimm that is at the heart of the Mu1.

The MU1 is fully custom when it comes to the upsampling from the AES and S/PDIF outputs.

Before I go further, let me talk about another company that is doing something similar (though not the same). Anyone who is interested in HiFi is most likely aware of the CHORD brand. Chord makes some amazing DAC’s with the DAVE, QUTEST and Hugo series. They also have something called an M Scaler that upsamples the music to a level that literally changes the presentation and makes digital sound much more human, rich, analog and real.

The Hugo 2 DAC and M Scaler will set you back over $11k and neither has a streamer built in. Even so, add a streamer and you can get some gorgeous sound from an M Scaler and Hugo/DAVE/Qutest.

The Grimm MU1 is not a DAC but does something similar to the $6k M Scaler BEFORE the music is sent to your DAC. In fact, I feel that the Grimm does best with NOS DACs or DACs that do not upsample (this is from my findings and tastes but you can use ANY DAC with the Grimm). The Grimm is upsampling before it hits the DAC so going right into a DAC with its oversampling turned OFF should yield the best results. But your ears and brain nay vary : )

The way the Grimm does what it does is rather amazing as the result is a sound so refined, so beautiful, so complete…it’s indescribable. I mean, I can not really describe what I hear as it is well above the usual intimate and emotional sound I am used to in this room. I will try to describe what I hear though as it is extremely rich, grand, alive, exciting and the scale is massive with the Fleetwood Deville SQ Speakers. It has that human touch and there is absolutely zero indications that I am listening to digital music when the Grimm is serving up the sounds.

When I go to other streamers I have on hand (Lumin U1 Mini, Rose 150b, Bluesound Node) they in fact do exhibit a flatter sound. A less fluid sound. A sound that does sound digital to me when compared to what comes from the Grimm. The sound from the Rose and the Node are without question duller and less exciting than the Grimm, even when just used as streamers. It’s absolutely incredible to experience this as it truly allows my system to be at its best with digital music.

The Grimm seems to have upgraded the sound of my DAC, my AMP and  my Speakers. The sound coming from the Grimm into a Denafrips Terminator Plus DAC is without question the best I have ever heard digital music sound, and better than any Analog I have ever heard as well. This is stunning to me.

It puzzles me as so many have always said “bits are bits’ but while this may be the case, what a streamer does to those bits before leaving does in fact seem to make a pretty drastic difference in the sound. 

One thing I can say is that with the Grimm in place of my Lumin U1 Mini or Rose 150b, the sound of my system went from incredible to something that sounded like a much more expensive and resolved/refined system. I mean, my system is very expensive as it sits with around a $40k price tag. The Grimm makes it sound like a $100k system, and that is just crazy.

Again, this is JUST a streamer/server I am taking about.

Before I sat down to write this, I researched others who have heard this piece as I wanted to make sure I wasn’t hypnotized or hallucinating, lol. After reading all I could find about the Grimm I learned A LOT.

I learned that just about anyone who heard one in their system, they have similar thoughts as I do. Reviews all claim this as the be all end all streamer and many reviewers have bought the review units for themselves. That right there will tell you many things. Reviewers get to hear A LOT of gear so when a reviewer buys a review unit, it has to be good.

THE MAGIC

The Grimm weaves its magic in very intricate ways. So much so, the technical details are beyond what my brain can handle. But it is all about the filters, low or no jitter/CLOCK, the FPGA card, a high power CPU and the ever so important resampling. The Grimm has all in place to do all of this with ease and accuracy.

The clock design is world class here and Grimm has gone to great lengths to customize and code their own chip, and while it is extremely expensive to do, it performs at another level vs off the shelf chips as we would expect.

THE GRIMM EXPERIENCE.

When the Grimm arrived I was very delighted with the build and design. It’s a sweet looking piece with the all matte black casing that is shaped and formed nicely. There is a big bronze/copper colored dial up top that changes volume and is used for pausing and getting through the very small and easy to understand setup menu.

This is not an overbuilt piece as it doesn’t weigh 80lbs nor does it appear to be chiseled from a solid slab of steel, lol. The inside looks basic but I can assure you that this streamer is anything but basic in its performance. There is a small screen on the front. No, it’s not a huge screen and it is nothing too fancy. There is a LED light that dots the “I” on the Grimm name. This light is bright.

When I paced it within my system I loved the looks. It’s basically a square box but the top really makes this streamer pop and scream UNIQUE. The dial up top is beautiful, feels weighted and while I doubt I would ever use it beyond initial setup it sure does add to the aesthetic of the Grimm MU1.

I simply took an AES cable, attached it to the AES out on the Mu1 and sent that to the AES in on the DAC. I attached one of my generic ethernet cables from my router to the input on the Grimm as well. I finally added two Cardas Clear Reflection RCA’s from the DAC outs to my integrated amplifier. Most of my listening here was using a Denafrips Terminator PLUS DAC, a Rose 150b DAC and a Weiss 501 DAC. I also tested it against a Lumin U1 mini streamer and my Bluesound Node (as a streamer only to the same DAC’s).

Going from the Lumin U1 Mini to the Grimm ($2k vs $11k). 

I have had the Lumin U1 mini for the last two years. I just sold it before writing this review as once I heard the Grimm I knew there was room for improvement in my digital front end. I loved my U1 mini and for what it cost ($2k) it has served my system well. It delivered music from Tidal, Spotify and Qobuz to my system with ease and without issues. In fact, I questioned why I would ever want more. The Lumin was an upgrade for me as I came from the Bluesound Node before that and the Node is the $600 all in one streamer and DAC that most of us start off with in HiFi.

A streamer is a streamer, right? 

So in goes the Grimm MU1 and I connect it to Roon within 2 minutes. It was simple to do. I setup the AES output for oversampling X4 (the recommended setting) and I set the Denafrips Terminator PLUS to NOS mode (NON Oversampling).

There was a much better flow to the music with the MU1. It sounded smoother, bigger, wider and more organic. It sounded somewhat like the Chord DAVE and M Scaler did with that ever so tangible presence and delicate, real and supple energy. It did not have the DAVE snap and pop though but the music had immense LIFE to it. The speakers were speaking truth in such a lovely way. The way the details flow sound like real music and nothing ever sounds out of place or off kilter.

Sometimes I listen to music and it just sounds off but never with the Grimm. No matter what I play it just does what it does and it does this so well.

The details are all here but they are delicate, airy and so present with some texture and foundation to each detail. The sound for sure sounds more “analog” which to me means richer, deeper, and more soul touching. There is absolutely zero sign of digital hash, strain or constriction with the Grimm in place. Wow.

It has allowed me to hear this hash and strain much easier though when I go back to other streamers. This is pretty cool as I didn’t notice it before I heard the Grimm in my system.

Going from the ROSE 150B as Streamer and DAC to the Grimm. 

The ROSE 150b is a stunning all in one DAC and Streamer for under $5k. It has beauty, brawn and features that are pretty impressive for the price point. While it is my fave all in one right now, it is not the best sounding or most refined as the DAC inside of the Rose is excellent but not up to the Denafrips or Weiss. Even so, I wanted to see what would happen if I sent the music from the Grimm to the 150b DAC and then compare the streamer in the 150b to the Grimm by sending both to the Denafrips.

The Rose 150b

Phew. OK.

So listening to the ROSE all in one was pleasant as an all in one. Worth the $5k for sure if this is what you need.

When I used the Grimm as a streamer INTO the ROSE, using the 150b DAC it improved the sound of the ROSE DAC and this was impressive. I turned off oversampling in the ROSE DAC and let the Grimm take over in that area. The sound, again, was smoother, bigger, more refined and without any digital gain. With the Rose on its own the sound is somewhat flatter and duller compared to using the Grimm as the streamer.

So the Grimm wins this battle, as it should. 

So now I test the streamer of the 150b into the Terminator PLUS DAC and I get an immediate improvement to the sound vs the 150b alone. I hear the Terminator PLUS character here which is gorgeous. Smooth, big, organic with weight but with amazing detail and such a quiet smooth sound. Much nicer than the 150b alone.

With the ROSE streaming into the Terminator I asked what more would ANYONE need?!?!? Well, I then attached the Grimm and replaced the ROSE for streaming and there it was again. Even more expansion in the soundstage and even more refined. More air, and more beef to the instruments. There was more texture and beauty to all of the music with the Grimm in place and all signs of these tunes being digital vanished.

So the Grimm wins this battle as well. 

With that said, we are talking that last 10-15% of sound improvement here. The Grimm delivers that for sure.

Compared to the Bluesound NODE

The Bluesound NODE is the streamer and DAC for almost everyone. If you are not obsessed with forever tweaking your system it the NODE is the streamer for you. It brings solid performance for $600 and includes a streamer and DAC with a wonderful APP. It streams Tidal, Qobuz and Spotify. It does it all, and its priced right. You can even buy them on Amazon.

How would a $600 all in one compare to the combo of Grimm MU1 and the Denafrips T Plus? I am talking a $600 all in one vs a duo that will set one back $17k.

Not fair? Well, no, so this is just for fun.

With the Node performing streaming and DAC duties the sound was very nice. Pleasant. Fat. Bass heavy and almost too much bass as it started to sound sloppy. This brings a nice big sound but listen closely and you may hear those digital artifacts as well. A treble that is more metallic than realistic. You may hear mids that are more sunken in than into the room Even so, it sounds great. Big, and yes I am swaying to the beat.

When I switch to the dynamic duo of Grimm and Terminator PLUS the sound changes in a big way. So much smoother, more analog sounding, more correct sounding, the bass is better and tighter with no boom. The magic is here in full effect as the music sounds less direct and more “in the room” and around my body. It sounds natural and there is an ease about it all.

Is this experience worth $16k extra (For the MU1 and DAC)? For most of us, no way. For some of us, without question it is.

The Grimm showed me it was the real deal, and that the hype owners have been gushing about is absolutely real.

HOOKED UP TO THE WEISS 501

The Weiss 501 is a true reference studio quality DAC. It has become one of my references this year due to the way it made music sound like reel to reel tape. With the Grimm attached to the Weiss the sound was very detailed, crispy and electric. It sounded alive. While I slightly preferred the Grimm and the Terminator PLUS combo more in this system and room, the Weiss was fantastic as usual with the Grimm.

WHO IS THE Grimm MU1 for?

This is not a piece for someone who has a $5k, $10k or even $15k system. For the Grimm to show you what it is made of, you must have some pretty high end and revealing gear after it. Your speakers must speak the truth. Your amp must be up to task. Your DAC should be world class. Only them would a piece like the Grimm MU1 make sense.

For someone like me, it makes sense. I have $20k speakers. I have a $10k power solution. I have a couple of world class DACs on hand. I have nice cables (they do make a difference with high end systems). I have a ROON subscription for life. I stream with Qobuz most of all and do have some local files I could store on an internal drive inside of the Mu1.

For me, the MU1 makes sense and after having it in my system for a while I have become accustomed to the sound it brings. It also seems to improve almost any DAC I hook up to it. Compared to the 150b, the U1 mini and even the Node it surpasses them as a streamer only into high end DACs due to the magic it is weaving through those selected outputs.

CONCLUSION

I was very skeptical of the Grimm MU1 due to the price tag. Then I remembered the Innuos Statement that is also just a streamer without a DAC and it costs more. I then researched and found more streamers that cost much more than the Grimm. So no, the Grimm is far from the most expensive streamer made today. It’s for sure the most expensive one I have ever tested or tried but this was because I always thought streamers were almost all the same. Minimal differences at best I said!

The Grimm changes those thoughts for me. After experiencing this streamer I now know what my system CAN sound like. As good as it is with other streaming solutions, it just is not as refined, smooth, expansive or organic without the Grimm in place.

Whatever supernatural goodness that the Grimm is doing with that upscaling on the AES and S/PDIF output, it’s really bringing in a big change within my system, for the better. I do not believe I could hear or bring digital music into my space with my gear that gets any better for me than what this MU1 is delivering.

It never breaks a sweat, no natter how complex the music gets. It stays composed, sweet, detailed, transparent, dynamic yet also places weight on the instruments and sound ensuring the music is never ever lifeless, sharp or fatiguing.

Do not take my word for it though. Read owners opinions. Read reviews from people who were just as surprised as I was when this little black box entered into their listening rooms.

While I do not feel an $11k+ streamer is for everyone, for those who are deep into this audio thing, well, it may be for you. If you have been wondering about what a world class streamer can do within your high end system I can tell you that the Grimm is absolutely fantastic and you should audition one if you can.

If I had a spare $10k I would own this streamer without question as my system truly benefits from it. It has brought big changes, and I have bought pieces in the past that have done this for my system. The Fleetwood Deville’s, The Enleum AMP 23R, the PS Audio PP20 were all pieces that blew me away moreso than competing products. So much so I bought them after review.

This Grimm is doing the same and while I have heard big time five figure digital front ends from DCS, CHORD, LINN and others none have sounded quite as delicious and complete as the Grimm (no matter the DAC I pair with it). 

It’s an end game streamer but wether it is worth it to you or for you is 100% up to you. All I can recommend is that you at least audition it if this review sounded like it was written for you ; ) Be aware though, if you do audition it be prepared to buy it as you will not want it out of your system once you have it in for a few days.

It may take a few days to really understand this Mu1 and let all it does for your music soak in. I know I have been stalling writing this review as I do not want to see it leave my room. The longer it is here, the more likely it is to stay put (and the more likely my savings account will dwindle more).

The Grimm MU1 is the real deal. A special piece made with love, care and passion in the Netherlands. For me, this is as good as digital gets.

See more at the Grimm Audio website HERE. 

PROS AND CONS

PROS

1. Beautiful Design. Looks beautiful.
2. Easiest ROON setup I have ever experienced and ROON is really top notch software.
3. Has digital INPUTS so you can hook up a CD transport as well. This means a boost to your CD performance as well.
4. You can purchase with an internal SSD to store and play your own music.
5. This is a streamer, a re-clocker and an upscaler all in one.
6. The best sound I have heard from a Streamer. Rich, fluid, free of all digital hash, noise, junk. Silent in operation. Sounds sublime into most DAC’s I have tried.

So with all of this goodness coming from the Grimm MU1, there has to be cons right? Well, here are the cons I found to be cons to me. 

CONS

1. It is expensive but we do get what we pay for in performance with this one. But this can induce sticker shock when looking at the price tag.
2. Only two outputs can be used for the scaling to happen, and this is what makes everything sound so good. Only the AES and S/PDIF outputs can be used going into your DAC.
3. Without the upsampling, this would probably be equal to the Lumin U1 which is half the cost. With the Grimm it is that 4X upscaling that creates the magic. It’s not so much different from adding a Chord M Scaler into the Mix but this is all inclusive with the Grimm.
4. At this time (Though updates are coming down the road) you can only use the Mu1 for streaming from Tidal and Qobuz and serving up music from the internal drives (if you have one installed) using ROON. Tidal Connect and Spotify connect are on the way via updates.
5. May be hard to find a dealer, locally.
6. The internals do not look like $10k and it includes a NUC with an i3 processor. I would have liked to see something like an i7 inside. Even so, I can not argue with performance.

Listening Notes 

So for this review I listened to an entire album through the Grimm as well as the other products I was comparing it against. The album I chose is the new release from Alanis Morrisette. It’s actually a meditation album with some incredible sounds, rhythms and instrument choices that will suck you into the music.

The Storm Before the Calm is an album that can easily show the differences between the Grimm, the Lumin and the Bluesound Node.

With the Grimm into the Terminator Plus the clarity, the depth and the realism was striking. At the same time, it was as effortless as it gets without any strain or edge to the music. It almost sounded as if the band was here, playing so gently, softly and intimately. I was wrapped in beauty for the almost two hours that the album lasts. The scale is also mighty impressive. This combo sounds large, lifelike, open and has that life and sparkle that connects us to the music.

This Alanis Morisette album is a purely instrumental affair filled with deep sonic landscapes. There is texture here as well and the album can sound anywhere from “wow, that was awesome” to “that was unbelievable”. How it sounds will depend on how your system decodes the bits. With the T+ and the Grimm, the sound is absolutely sublime.

The same can be said with the MU1 going into the Weiss 501 but instead of the warmer wider presentation I was now getting the same smooth detail but with a more impactful presentation. The soundstage was not as wide as with the T+ but the sound was cleaner still and had a bigger bass impact. There was also more of that studio sound that the 501 brings. With the Grimm I preferred the Denafrips within my system.

When I switched to the Node being used as a streamer into these DACs the sound flattened up some, became warmer and more bass heavy. This in turn took away some of the transparency, clarity and realism.

Do not get me wrong though. The Node sounds great here when going into the same DACs but it’s not quite the same. I can easily hear the improvement and yes it does seem substantial.

Using the Node all on its own with its internal DAC makes things worse for the $700 box. Now the sound is darker still and the top end more subdued. The mids are more sunken in vs going into the external DACs and the bass has some boom, losing a little control. The music from the album now sounded like a recording that was being reproduced in my room.

With the Grimm the music just sounds alive, as if it is a living breathing life force. The Node shrunk the music to some degree when used as one box solution. I noticed that by track two I started to get a little bored the using just the Node. Hmmmm.

With what I have on hand, for me and my system, the Terminator PLUS with the Grimm rules the day. A great combo but the Grimm sounds wonderful with every DAC I have thrown at it. In fact, I believe spending more on the Grimm and a little less on the DAC may make sense in this case. I believe the Grimm may add more to your digital streaming than just a DAC as it will make almost any capable DAC sound beautiful. It will improve the DAC you have but it will also show you more of what it can do when you attach a world class DAC to the MU1.

The Bottom Line

If you want to just enjoy the music and never think about what streamer can improve your music further, take a look at the Grimm my friends. The MU1 is the finest music streamer I have ever encountered when it comes to sound quality and it is also quite striking in design. It is expensive but it does deliver the goods if your system is up to the same level as the Grimm.