SOtM Digital Stack: A Deep Dive Into High-End Digital Audio Playback

Explore how the SOtM digital stack transforms streaming with superior sound quality and modular upgrades for audiophiles.

From CD Players to Streaming: The Digital Audio Evolution

Digital audio has traveled a fascinating journey, and I still vividly recall my first quality CD player by Mission. That player stood out because it avoided that harsh, edgy grain in the highs that often leads to listening fatigue—a common issue with many devices back then. Even today, I'm reminded of a few DACs and players that chase detail in the upper frequencies but at the cost of a touch of sharpness that wears on the ears.

Fast forward to today, and CDs are nearly extinct. Streaming has taken the spotlight, and services like Roon, Qobuz, and Tidal have become my daily go-to. With innovations like Qobuz Connect and Tidal Connect, the music streams directly to your DAC or streamer, bypassing intermediate servers often used with Roon. This direct path elevates sound quality, now surpassing even traditional Red Book CDs in resolution and richness.

Back in February 2023, I had the pleasure of reviewing Rose 150B streaming DAC. Rose, a fellow Korean brand like SOtM, impressed me with its excellent build, sound, and user-friendly design. I was so taken by the 150B that I ended up buying the review sample, and it remains part of my setup today.

Discovering SOtM: Soul Of The Music

When Robert Harley invited me to review the SOtM sMS-2000, I dove right into research. SOtM, which stands for Soul Of the Music, was new to me. Founded in 2008 in Korea and available in the U.S. since 2010, SOtM originally rooted itself in PC audiophile playback. The sMS-2000, unveiled at High End Munich 2024 but only widely distributed about a year later, intrigued me immediately with its unique design.

This device isn’t just a Roon Server (previously called Roon Core); it's also an audiophile-grade USB digital output streamer. By combining the server and streamer in a single box, SOtM achieves lower jitter and better sound purity—a core philosophy of their design.

Because I lacked a DAC with a USB input, I also requested the accompanying SOtM sDP-1000EX DAC. But SOtM’s generosity didn’t stop there—they sent along their modular USB filters tX-USBultra, the master clock sCLK-OCX10, and four separate power supplies. I began with the DAC and gradually added pieces, exploring the upgrade path rather than reviewing a single product. This journey proved fascinating.

The Starting Point: The sDP-1000EX DAC

The sDP-1000EX is a high-end DAC supporting 32-bit/384kHz PCM and DSD formats. It features USB inputs and can double as a preamp, though I didn’t delve into that. I initially paired it with a Wattson Audio Madison LE streamer using an AES/EBU balanced connection.

At $3,630 plus the mandatory SOtM sPS-500 power supply at $650, the package totals roughly $4,300. The sound was surprisingly good for the price—the playback was clean, with only a touch of grain. The bass was notably impressive, an area where many DACs stumble. The soundstage width excelled, though depth was a bit shy of ideal. Smaller ensembles sounded clear, but large groups like big bands brought some challenges. Still, orchestral recordings exhibited exceptional clarity and definition. While not the most formidable DAC I've ever heard, it proved strong competition in its range.

Revisiting PC Audiophile Roots

Knowing SOtM’s PC audio origins, the architecture of the sMS-2000 is essentially a custom Linux PC optimized for audio. Fifteen years ago, I experimented with a quiet Windows PC dedicated to audio playback, using a separate USB card and power supply feeding digital signals to my DAC. Though a neat experiment, it lacked the seamless integration and sonic finesse I crave.

One major limitation was J.River’s lack of support for Qobuz and Tidal. Enter Roon, with its brilliant ability to unify your ripped CDs and streaming libraries into one seamless interface. It’s a dream come true for music lovers who want effortless access to everything without worrying about the source. Plus, Roon’s rich artist notes and connection graphs add a delightful layer of discovery.

SOtM sMS-2000: Where Digital Audio Magic Happens

SOtM’s proprietary Linux-based OS, Eunhasu, is tailor-made for high-end audio. It offers playback customization options, including CPU speed adjustments. The sMS-2000 is packed with custom boards designed to minimize noise and jitter, especially in its dedicated USB and network cards powered by an external sPS-500 power supply.

Priced at $10,350 (including USB and network cards), the sMS-2000 paired with the SOtM dCBL-UF USB cable ($1,020) completely transformed the listening experience on the sDP-1000EX DAC.

The first thing I noticed? The upper-frequency grain vanished while preserving all the delicate detail. Next, the soundstage depth was something I’d never achieved with digital playback before—approaching the immersive feel of my analog rig. Finally, the instruments came alive with remarkable dimensionality and texture—drums, saxophones, cellos, even vocals felt palpably real, bursting with micro-harmonics that give live music its soul. This was a genuine leap in digital fidelity.

Pushing Boundaries: Adding Filters and Clocks

With four of nine components now installed, I still had the tX-USBultra USB filters, sCLK-OCX10 master clock, and extra power supplies to test. The first USB filter upgrade, at $1,400, smoothed the overall sound presentation and slightly enhanced micro-harmonics and bass richness. It was subtle but meaningful.

Adding the $3,900 master clock (plus $820 cables) was another game-changer. The clock anchored each instrument solidly in space, improved bass, and maintained clarity without harshness—a level of polish that was unmistakably higher.

Curious about the second USB filter, I was surprised to find it provided improvements on par with the first—though not essential, it further refined the soundstage and textures.

Tweaking the System: CPU Speed and Tuning

One of the coolest features of the sMS-2000’s OS is the ability to adjust CPU speed. Founder Sean Lee suggests slower speeds reduce noise but may introduce latency. At default 3.6GHz, the soundstage width matched speaker placement, but dropping to 1.2GHz expanded the soundstage dramatically, adding a surreal scale to orchestral works.

That lower frequency also magnified micro-harmonics in small jazz combos—almost like an X-ray into the music. I found that a bit too intense for everyday listening. Settling on 2.2GHz offered a balanced sound for both classical and jazz, striking a sweet spot.

Tuning options also allowed subtle tonal shifts, with latency performance mode emerging as my preferred setting.

Final Upgrade: The Network Switch and Clock

Network quality is vital in streaming setups. In my system, a Luxul router fed audio gear directly, bypassing some switches. Previously, I used a Trendnet switch paired with an EtherREGEN filter before the sMS-2000.

SOtM’s sNH-10G network switch ($1,900) promised improvements. Without its 10MHz clock, the switch offered a smoother, deeper bass but tamed the attack and highs a bit too much for my taste.

Installing the 10MHz clock with power supply and BNC cables was nothing short of magical. The entire system's fidelity surged—bass extended naturally, highs became crisp without harshness, soundstage depth broadened, and instrument textures blossomed with lifelike authenticity. Aside from the sMS-2000 itself, this was the single most profound upgrade.

Conclusion: A Tour de Force in Digital Playback

The SOtM digital stack, starting with the sMS-2000, offers an innovative architecture that invites audiophiles to build an exceptional digital playback system piece by piece. This modular approach is a joy for those who love to chase incremental sonic improvements.

The combined performance of these products challenged—and in many ways surpassed—my analog front end. The standout achievement was capturing the natural, textural essence of instruments, something I’d always leaned on analog playback to experience.

SOtM’s suite represents some of the finest in digital audio today and might very well reshape my serious listening habits moving forward.

If you desire streaming digital excellence with a realistic upgrade path and stellar sound quality, SOtM’s offerings come highly recommended.

Specs & Pricing Overview

• sMS-2000 Server: Linux-based high-end audio Eunhasu OS, Roon Server, DLNA, UPnP, network streamer, storage up to 48TB, USB output
  Price: $10,250
• tX-USBx10G USB Card: Included with sMS-2000, also sold separately
  Price: $550
• sNI-1G Network Card: Included with sMS-2000, also sold separately
  Price: $550
• sDP-1000EX DAC: 32-bit/384kHz PCM, DSDx64/128, USB, BNC, AES/EBU inputs, balanced/unbalanced outputs
  Price: $3,630
• tX-USBUltra USB Filter: USB input with two outputs, requires separate power supply
  Price: $1,400
• sCLK-OCX10 Master Clock: 10MHz clock generator
  Price: $3,900
• sPS-500 Power Supply: Various DC voltages
  Price: $650
• sNH-10G Network Switch: 8x RJ-45 ports, 2x SFP ports, supports 10/100/1G Ethernet
  Price: $1,900
• dCBL-UF USB Cable
  Price: $920–$1,020
• dCBL-BNC Cable
  Price: $820

Total system price as reviewed with all upgrades: $35,940

Associated System Components

• Loudspeakers: Talon Phoenix
• Subwoofers: 2x Talon Thunderbird (with Rives sub-PARCs)
• Amplifier: VAC 30/30 (300B-based)
• Preamplifier: Mark Levinson 380S
• Turntable: VPI TNT MkII (modified)
• Tonearm: Graham Phantom B
• Cartridge: Air Tight PC-1 Coda
• Phonostage: Aesthetix Rhea Signature (Telefunken tubes)
• Digital: Wattson Audio Madison LE Streamer
• Cables: Kubala-Sosna Emotion Series

"I could hardly believe I was listening to the same digital-to-analog converter. This was a refined, super-high-end digital playback."

— Reflecting on SOtM sMS-2000's impact on sound quality

FAQ

• What makes the SOtM sMS-2000 unique compared to other digital servers?
  It combines a Roon Server and audiophile USB digital output in one unit, reducing jitter and improving sound quality by integrating server and streamer functions.
• Can the SOtM system be upgraded over time?
  Absolutely! The modular nature lets you add USB filters, master clocks, and power supplies to enhance performance step-by-step.
• Is the sDP-1000EX DAC suitable for all music genres?
  Yes, it handles everything from small jazz ensembles to large orchestras well, with excellent bass and clarity, especially when paired with the sMS-2000.
• Does adjusting CPU speed on the sMS-2000 affect sound?
  Yes, lower CPU speeds tend to widen soundstage and enhance micro-harmonics but may increase latency, allowing tailoring to your listening preferences.
• How important is the SOtM network switch and clock?
  Very important. The network switch smooths and deepens the sound, while the clock dramatically improves overall fidelity and instrument clarity.

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