Anyone jump from Nucleus to Grimm MU1?

I have a chance to get a MU1 for my Roon duties - could replace my Nucleus.
Did one here take that step already and if so, please what are your thoughts SQ wise! The Grimm is almost 10x more expensive- so I hope :wink: there is a SQ improvementā€¦
Many thanks!

I have not but I know the Grimm gets a lot of respect. I think the MU2 may have been Stereophileā€™s digital component of the year (or there was a tie).

FWIW I moved away from Roon after my Nucleus+ died. I just gave up on Roon and focused on other options. That said, the Grimm could both improve SQ and be more reliable.

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Just one caveat to keep in mind, IINM, the Grimm MU1 is relatively underpowered for a Roon server and has an upper limit of supporting only 100K tracks.

IMHO, the MU1 only makes sense if youā€™re intending to use itā€™s AES outputs and upsampling. Otherwise stick to a COTS Roon Server instead.

Thanks Anup, never thought about that- my guess was that MU1 is ā€œbuild for roonā€!

Not really.

As I understand it, the MU1ā€™s primary focus is as a digital signal processor (up/down sampling, with dedicated FPGAs) & re-Clocker, with AES/EBU as its preferred output.

For Roon duties, apparently it uses a stock Intel NUC Core i3 & 8GB RAM - in order to keep the unit fanless. As most Roon users would know, an Intel Core i3/8GB only just meets Roonā€™s most basic hardware requirement. Generally speaking, I donā€™t think Roon on the MU1 is going to be a good user-experience.

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It actually depends on the i3 generation.
A gen 14 i3 can totally outperform an gen 7 i7 for example.
Where the cpu is the more solicited with Roon is regarding its DSP feature, but as I understand it thereā€™s some hardware dedicated to it in the mu1, so an i3, even old gen, may suffice.
Iā€™ve been using an old i3 on a Mac mini to run Roon for 5+ years with no real performance issue.
I ended up migrating to a Roon ROCK NUC with a gen 14 i3, because I was mainly fed up with constant OSX updates and maintenance.
The only difference is the interface is slightly more responsive but itā€™s not night and day difference whereas there is twice more RAM and the CPU is at least twice faster on the NUCā€¦

Unfortunately, according to the Grimm Manual, recent MU1s are Kaby-Lake Core i3-8109Us; if Iā€™m not mistaken thats 7th or 8th Gen Intel Processors. It also runs on 4GB of RAM (not 8GB as I stated previously). This thing will be a bit of a dog with most Roon collections :laughing:

Ok, then safer to keep the MU1 as a Roon endpoint only rather than a Roon server+endpoint.

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I use an MU1 simply because itā€™s easily the best sounding Roon implementation Iā€™ve heard. Iā€™ve had it it for about two years or so. Had no problems at all, but then Iā€™m not using any downloaded files on disk. I use it mostly for Qobuz streaming.

Thanks Martin,
so youā€™re streaming from MU1 via LAN to dCS?
Or do you use MU1 direct attached (AES/SPDIF) to dCS then?

  • and what Roon server did you use before please?
    Thanks!

The MU1 is directly connected via AES. I didnā€™t use Roon prior to owning the MU1 as sound quality seemed to suffer with each system my dealer demonstrated. Ethernet radio does sound better using Mosaic though.

Thanks, so you prefer music over MU1-AES-Rossini and radio with Rossiniā€™s internal streaming capability. Thatā€™s interesting and confuses me even more :wink:
I really thought that MU1 is the best roon server out there but all comments here say no :slight_smile:

Iā€™m chiming in as Iā€™ve been using the MU1 as a Roon Nucleus Plus replacement for a couple of years. Itā€™s far better sonically. Mine runs an i3 with 8 GB memory. Having used an early Nucleus with only 4 GB memory, I discovered that bumping up memory made the Nucleus far more responsive, and though I use no DSP functions, less likely to crash.

However, since my library has grown to well over 100k tracks, I decided to offload the Roon Server burden from the MU1, by using a MacMini M1. Not only did it make the overall experience of playback faster, mostly in its operation with my iPad Pro, but surprisingly - sonically better. No clue as to why this might be the case, though Roonā€™s implementation on MacOS is likely different than using Tiny Linux on the MU1. Iā€™ve also found in my testing that though quite good, the MU1ā€™s upsampling cannot best that of the dCS.

As for the signal path all roads lead to the Uptone etherREGEN switch. All music resides on a Synology NAS. From there to the MacMini ā†’ MU1 ā†’ AES/EBU to Vivaldi Upsampler ā†’ Vivaldi APEX DAC, etc.

Happy to share any other details of MU1 endpoint implementation or system bits.

I will say, having recently listened to the new dCS VarĆØse stack compared to the the Vivaldi, itā€™s quite a step up, even if the associated system components, especially the preamp/amp used, could be bested by other equipment. Iā€™m hoping for a future audition using Spectral gear and maybe a Grimm MU1.

Returning home soon after to my system, it was surprisingly not as big a let down as Iā€™d expected. Considering the replacement cost, Iā€™m inclined to await further ā€œtrickle downā€ upgrades from David, Andy and Chris.

Thanks Steve, thatā€™s really interesting!
So reading your findings, you rate the MacMini roon SQ better than MU1 and itā€™s better than Roon Nucleus as well (some may say thatā€™s impossible to spot any SQ differenceā€¦)
Would you get better SQ if the MU1 was pimped up (more CPU power, more memory) then?
And why do you use the MU1 then if you can stream directly from M1 with roon to the upsampler?

No. Sorry for any confusion. What Iā€™d hoped to convey is that moving the Roon Server function off of the MU1 was intended to relieve the MU1 of the i3ā€™s work in dealing with Roon. As an FYI, the existing Roon Server in the MU1 still is ā€œrunningā€ but performs a sort of ā€œbridgeā€ to the FPGA, where the real magic happens.

I have not tested using the MacMini M1 bypassing the M1. That would alter things a bit. Instead of the AES/EBU connection Iā€™d be using a network connection. And years ago I found that using a Mac of any kind as a Roon server less sonically competitive with alternatives.

Thereā€™s much more going on in the MU1. The hardware is seemingly immune to outside influences - testing with better/different power or Ethernet cables show little impact, though the output benefits in using AES/EBU and, at least with my HRS racks, using after market feet, helps sonically. So, Iā€™d say the MU1 is more than a sum of its parts. Best to find a dealer who can lend one to you for a trial.

Meanwhile, Iā€™d suggest you visit this forum which has much more focus on the Grimm servers, lately their MU2: https://audiophilestyle.com/forums/topic/58754-grimm-audio-mu1-and-mu2-music-players/
As you can see itā€™s been around for quite some time. My recent post on offloading the Roon Server starts here: https://audiophilestyle.com/forums/topic/58754-grimm-audio-mu1-and-mu2-music-players/page/88/#comment-1294095

Thanks Steve,
the MU1 sounds very promising, think Iā€™ll put it on my ā€œnext upgrade stepsā€ list :wink: !