Review: Grimm Audio MU2 Music Player

If you want to hear the best digital music reproduction I’ve heard by an obvious and distinct margin, you’ll need to find a Grimm MU2 to listen through.

That’s it, that’s my conclusion—the Grimm MU2 acting as Roon server, Roon endpoint, and DAC made music sound at once less processed and more fully fleshed out than other digital solution(s) I’ve had the pleasure of hearing. What’s more, the MU2’s analog volume control and line level inputs turned it into a wonderful sounding preamplifier to boot. All in one.

The Grimm MU2 can act as a Roon Core (server), Roon Endpoint (streamer), DAC (digital to analog converter), and analog preamp all in one, which is the way I used it for most of the serious listening part of this review. The internal SSD storage is optional and comes in two sizes: 2TB or 8TB and adds $235 or $630 to the MU2’s price respectively. Money well spent as far as I’m concerned. Now I know some people wonder if (or pretend to know that) having a server, streamer, and DAC all in one box may compromise sound quality and I can tell you that is just not the case with the Grimm MU2. No way, no how. How do I know? Because of how it makes music sent through it sound.

The comparisons used for this review included the Barn resident Auralic ARIES G1.1 (review) streaming to with the review sample totaldac d1-triunity (more info) or the Barn resident Mola Mola Tambaqui (review) through a length of AudioQuest Diamond AES cable. The larger systems pictures included the Audionet HUMBOLDT integrated amplifier (more info) driving the recently reviewed Vivid GIYA G3 Series 2 speakers (review), the Treehaus Audiolab ‘Phantom of Luxury’ Field Coil Loudspeakers (more info) paired with a few different amps, the Barn resident DeVore O/96 powered by the Barn resident Leben CS-600X or the Triode Evolution 300 Integrated Amplifier (more info) with everything wired by cables from AudioQuest (full system and Barn details).

Listening took place over a 2-month period with the MU2 seeing play time on the Barn’s A- and B-Sides. Lots of different gear/systems, lots of music, and loads of cursing, that’s a NJ-native’s highest form of praise, and head-shaking at how deeply the MU2 digs into digital music and pulls out a fully formed fleshy humanness better than any other digital I’ve heard in Barn.

The MU2 includes both RCA and XLR outputs and perhaps less expected RCA and XLR inputs which means you can connect your phono stage to the MU2 and use its relay based analog volume control turning the Music Player into an analog preamp to boot! There are also 3 digital inputs (AES, Coax S/PDIF, Optical), an Ethernet input (no WiFi here), a USB Type-A slot for adding USB (music) storage, and a headphone jack. Full fun(ction).

Grimm offers a very nicely written explanation of their Major DAC on the website. Here’s a taste:

…The implemented solution in the Major DAC results in a zero error operation of the noise shaper. Moreover, the 1.5 bit DAC choice offers such a stable noise shaping operation that it allows for a highly optimized, unique 11th (!) order noise shaper.

To filter the resulting strong high frequency noise before it enters the analog signal path a so-called FIR DAC topology is employed, using 16 DAC cells per channel. And while we are on the topic of filtering: worth noting is that the input of the noise shaper is fed from our extreme precision “Pure Nyquist” digital FPGA filter, running at 128 times the base rate. All these measures enable the Major DAC to reproduce micro-details in the audio that have never been heard before.

I’ll repeat that last bit because it’s relevant to what follows—All these measures enable the Major DAC to reproduce micro-details in the audio that have never been heard before. And I recommend reading the full explanation here.

But who really needs micro-details. Isn’t that some audiophile obsessive amusical stuff like hearing chairs creak and bassoonists burp? On the contrary—micro-details are the place where music’s soul lives. More on that in a minute.

That silver wheel up top offers a number of functions including volume control, mute, input selection, Line / Headphones out toggling, and access to the MU2’s menu system. For anyone interested in the fine print, I recommend reading both the Hardware and Software Manuals for the MU2. I preferred controlling all playback-related functions using Roon on my aging iPad or iPhone with an occasional peek at the MU2’s rudimentary browser-based interface.

While I try to avoid potentially divisive topics, I am a fan of consolidation when it comes to digital—when done right. The Grimm MU1 (review) is one great example as it combines a Roon server and endpoint in one box (and more) while offering superb performance sonically. A win win win. The MU2 takes that a few steps further adding a DAC, analog preamp, and headphone amp while also offering superb sonic performance. I believe that’s a win win win win win win. I also like the way both Grimm units look and feel. Another win.

I’ve been hearing, for decades, people say something along the lines of, “It doesn’t make sense to spend too much on a DAC or invest in an all-in-one solution because digital changes and evolves all the time.” The thing is, it really doesn’t. A good sounding DAC from 10 or so years ago, like the totaldac d1-tube MK2 (which I reviewed for Stereophile in 2015), is still a good sounding DAC today. Besides, the notion that I should put off today’s enjoyment because there may be something even more enjoyable tomorrow strikes me as waiting not living. No thanks.

All that being said, I usually end the consolidating before a preamplifier and have said on many occasions how I prefer a preamp, or integrated amp, in my system. In my experience, using a digital source to control volume and eliminating or bypassing a preamp or integrated amp’s own preamp section generally made music sound thinner and less fully formed. Kinda bleached or undernourished generally speaking. Nearly anemic in the worst of cases. But the Grimm MU2 has proven my generalization wrong. I let its internal analog preamp take over for the internal preamps in the review Triode Evolution 300 and my beloved Leben CS600 and I didn’t feel as if I, or the music, lost anything. In fact there was an added clarity and transient speed that I preferred with the MU2 in charge.

South-Asian vocalist, multi-instrumentalist and composer ganavya’s like the sky I’ve been too quiet, released on Shabaka Hutchings’ Native Rebel Recordings earlier this month, is a study in quiet, intense beauty.

From an interview with ganavya on Headliner Magazine:

“I trained in Carnatic music,” she nods, using the background noise in her apartment during the interview as an example: “I can hear two separate planes that are running; there’s one car, there’s a fridge motor and a small fan that I can hear from one story below. The bathroom on the left side also has a small fan, and even though I don’t have perfect pitch, all the notes are forming a song in my head. The ability to relate very quickly to the intervals is something that Carnatic music and that my mother and my grandmothers have taught me.”

The sonic strengths of the Grimm MU2 perfectly capture and reveal all of the notes on like the sky I’ve been too quiet from ganavya’s hushed vocals to birdsong to bass, electronics and more brought into play by guests artists including Kofi Flexxx, Floating Points, Carlos Niño, Leafcutter John and bassist Tom Herbert. This is peaceful, ruminative music that lives and breathes in subtlety, the delicate interplay of layered sounds and sitting on the Barn’s B-Side with the Grimm feeding the Leben CS600X’s Pre In driving the DeVore O/96 I was completely transported, held aloft by the gentle breezy beauty of like the sky I’ve been too quiet. Subtle yet stunning.

I’m reminded of and was inspired to play my LP of Alice Coltrane’s Kirtan: Turiya Sings that features only Coltrane’s voice and Wurlitzer electric organ. Released in 2021 on Impulse!, I let the Barn resident Michell Gyro SE Turntable/Sorane SA1.2 Tonearm mounted with the EMT HSD 006 MM cartridge dig into the grooves, sending the signal out to the Manley Chinook SE Phono Stage and into the Grimm MU2’s analog input and out to the Leben CS600X.

This is devotional music pared down to the intimate, songs of praise, and this system brought me into deep communion with its otherworldly beauty. While the initial intent was to ‘test’ the Grimm as analog preamp with an analog source, I never got to the ‘test’ bit as the MU2 passed with flying colors a few notes in as I was once again taken away by the music in play where the MU2’s delicate precision was readily apparent even when run as preamp playing the infinitely lovely music of Alice Coltrane on vinyl. Bravo!

I let Niecy Blues, Mary Lattimore and the Meze Audio 109 Pro headphones sing to me about the MU2’s headphone amp and it, unsurprisingly, sang a very similar sweetly refined song. I admit I did not spend a lot of time listening through the Meze ‘phones even though the sound was perfectly captivating because I was having way too much fun letting music flow in the space of the Barn.

Natural Wonder Beauty Concept is the self-titled debut from the duo Ana Roxanne and DJ Python (Brian Piñeyro), released in July of this year on Mexican Summer.

From the liner notes:

Brian and Ana converged on Kranky label manager Brian Foote’s home studio in Los Angeles in the summer of 2022. The songs were taking shape. Dreamy, densely layered drum programming and atmosphere, redolent of Seefeel and Boards Of Canada, washed against jungle and oddball ambient landscapes. They listened to tracks-in-progress while driving through the hills at night, lights flickering out in the expanse. The writing process was entirely collaborative. Ana sang, Brian sang. They dashed off lyrics together, reflecting an increasingly shared mental state. “You me you / falling in deeper blue / running through a circle that surrounds you / mango jelly flowers all around you.”

One the biggest of the MU2’s many surprises was just how expert it was at getting out of music’s way while leaving behind the most finely refined and revealing re-production in its wake. The music contained on Natural Wonder Beauty Concept stutters, stops and starts as if made by some elaborate soulful automaton with electronic sounds emerging from silence in reach out and touch it dimensional form feeling as real as bubbles floating in air. The review system comprised of the Vivid GIYA G3 Series 2 speakers driven by the Audionet HUMBOLDT integrated amp was, along with other things, a master of purity in sound, extra especially so when paired with the MU2 making this rich dense dance of a record come to stunning life in Barn.

Part of my review routine is running systems 24/7 with Roon Radio in charge of the overnight playlist. And I get a real kick out of coming into the Barn in the morning to hear where Roon Radio has gone in my absence, the further from the familiar the better. But it was in listening to the familiar that highlighted the Grimm MU2’s exceptional performance as I heard more deeply and more fully into the sounds of familiar music than I’ve ever experienced in Barn. And the degree to which the Grimm’s ultra-clarity, dimensional wholeness, and superlative resolution had me cursing in delight and shaking my head in wonder at the new sounds from familiar music even after more than a month of listening. That, in and of itself, is remarkable as the ‘new’ sounds of a review component typically fade after days.

I ran through countless familiar ‘test tracks’ with the MU2 acting as Roon Server/Endpoint/DAC/Preamp and the connection to the intricate workings of the whatever music was in play made the listener/music bond immediate, deep and endlessly delightful whether that music was the Indonesian blues of “Kabau” from Alkisah by Senyawa, the soulful stirrings of Nina Simone’s “I Loves You, Porgy”, “Faint Heart” from Hee Haw by The Birthday Party, “Sugar Bee” from Swampland Jewels by Cleveland Crochet & Jay Stutes, or Martha Agerich’s take on Bach and on and on. From the most dense electronic mass of sound to solo piano and everything in between, the Grimm MU2 pulled out the richest and most fully resolved sounds of music I’ve had the pleasure to live with.

I know what some of you are thinking—Did you try the MU2’s digital inputs with an outboard streamer to see if that’s even better? Or—Is the Grimm MU1 paired with some other DAC and a real high-end server even better than the MU2 package? And my answer is you haven’t heard what I’ve been saying…

If you want to hear the best digital music reproduction I’ve heard by an obvious and distinct margin, you’ll need to find a Grimm MU2 to listen through.