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Gain. Nelson Pass' favored Jfets are super suave power devices but not muscle-bound gorillas. They provide sufficient not excess gain. With the push/pull FirstWatt F6 this had the SOtM at minus 25dB to match the Job's minus ~40dB. Depending on mood and material, I could listen as high as minus 10dB. If the control were a rotary type the F6 was between 3 - 4:30 o'clock. This too gets certain folks jittery. Here it's for no good reason. That's because the ideal system would require no attenuation at all. You'd connect source to amp without any volume control and enjoy perfect loudness. Shy of that you'd want to throw away as little precious signal as possible. The closer your volume control sits to max the less resistance blocks the signal. If max got as loud as you'd ever want, it'd be mission accomplished with zero casualties. End of detour. But on this subject the sDP-1000's range of 10dB gain above its nearly 4V of unity gain accommodates even rare power amplifiers of lower than 4V input sensitivity where the designer counted on high preamp gain. So SOtM gauged things just right.
With FirstWatt F6
If we presume the sDP-1000 to be mostly neutral—properly designed digital should be—final sonics become a function of the amp/speaker interface. There's no added upstream flavor. With the sDP-1000 those who'd usually reach for a valve preamp to inject extra body or textures from a strategic THD shift lack that perfume dispenser. Unless they tossed SOtM's core functionality to the wolves. They could run at 00.0dB unity gain to follow up with an active linestage. But that'd defeat the purpose so we won't go there. Though one could. No law forbids it. To isolate sonics versus my well-regarded Metrum Hex, I handled USB-to-S/PDIF conversion externally. My dX-USB HD & mBPS-d2s are what's inside the sDP-1000 and superior even to Metrum's own implementation of 24/192 asynchronous USB without PC power. Now I connected both DACs to this USB bridge. The Hex then tapped into the sDP-1000 via XLR analog to suffer through one extra interconnect. Because of SOtM's ultra-convenient volume memory for each input, I only had to match loudness once per track. Afterwards I could shuttle back and forth with a single wand click and not mess with reseating the USB cable and pointing PureMusic 1.89g at a new source.


As it should have been with well-executed recent digital gear priced within spitting distance, this was a close call primarily distinguished by texture or sheen. The Hex played it drier, its surfaces were matter. The SOtM was wetter and glossier. On material with generous or gratuitous reverb, this attribute became more difficult to nail. On material recorded in less reverberant environs (or not seasoned afterwards with electronic reverb by the mastering engineer) it became easy to pick out once I knew where to focus.


The Hex drilled down deeper into multi-tracked affairs where for example the lead singer was recorded elsewhere to be spliced in later. With the Hex the reflective halo around the vocals then was more clearly different from or other than what surrounded the instrumentalists as audible space. Not one virtual venue but two. The sDP-1000's innate shift deeper into decays which create wetness in the first place meant that this type of difference shrunk and became harder to detect.


In mundane terms we all know this effect from moving. So UHaul alert. Whilst our absorptive or diffractive furnishings are still in the van, the hard reflective surfaces of an empty flat or bungalow create longer reverb and our so very familiar voice becomes richer particularly in the shower. Once our overstuffed sofa, carpets, pillows, curtain, bookshelves and plants move in, this wet acoustic dries out. Decays shorten, our voice returns to normal. Dilute this effect from heavy to feather light. What remains is the core distinction between Hex and sDP-1000. It's directly related to how valve gear tends to differ from transistors. Talking in generalities, transistors are drier and better separated, valves wetter and slightly fuzzier. Given how the vast majority of hifi systems runs on transistors, this voicing is clever and compensatory. It anticipates a potential shortcoming with a sound that's too damped to build in a very mild antidote.

To extrapolate, this compensation affects tone richness (+), connective tissue (+), separation (-) and intelligibility (-). To visualize the two minuses, play piano for a few seconds with the damper pedal depressed. Until you release the pedal, all notes linger, mix and run into each other like water colors. The extent to which SOtM lifts this damper is minuscule. It's less than a fraction of a milli second. Yet it's there and in an all-transistor context a very attractive bonus. If we spin out this observation, extremely rapid arpeggios will obviously blur just a tick just as a drum roll would in a church. The more complex and quickly changing music becomes, the more separation is needed to keep it pristinely clear. By the same token your average audiophile vocal Jazz trio is comparatively sparse. That sparsity gets a little fuller when we dial up the reverb.

Before we take things too literal, the kind of difference one hears with these converters obviously isn't really about longer or shorter decay times or hidden damper pedals. It's about a different weighting of THD. Our brains simply interpret that as related to these familiar effects. The upshot here is to think of the sDP-1000 as containing an invisible tube of the ultra-linear C3m type. It's invisible because it's not there, period. It's also not there as any noise or curtailed bandwidth. The only footprint our non-existent tube leaves is this subtle wetness which will never wear out or need replacing. And that's sweet!

Having spilt many a pixel on the Metrum Hex and AURALiC Vega, I get those interested in greater detail to refer to their reviews. That's because sonically the SOtM sDP-1000 sits right between them! It also does on DSD where the Hex goes none, the Vega double. On vital features meanwhile the SOtM is the only one to act as a true analog preamp with three non-digital inputs and analog-domain volume. The only competition here I've heard comes from Igor Levin's Antelope Audio with their Zodiac Gold model (Platinum forthcoming). But sonically the Gold does away with the virtual tube. Its calling card is airiness instead which adds a virtual super tweeter.

My few nits about the SOtM other than its oddly spelled model name aren't about sonics or features but two small items. There's the remote's very narrow angle of acceptance which renders it useless should your source stack sit on the side rather than front wall and necessitate greater than 45° angles. That needs to be improved. In our age of playlists where one track recorded at one level is followed by one from another album with a different median value, endless volume trims during a single listening session are perfectly normal. Hence it ought to be executed from the seat. Nagra's wand is a perfect example for a very broad acceptance window. Finally the display can't be extinguished. It'd be nice if it could. And that's it. On options, the sPS-1000 is overkill for just charging the sDP-1000's two batteries. It does however eliminate a nasty switcher on your power line. If you had a digital-direct iPod dock or small phonostage that runs off a 5, 5.5, 6 or 7V wall wart, the third socket nets you a proper linear supply. That should make for a noticeable sonic improvement just as Antelope's Voltikus supply does for their DACs with stock switchers. Once someone adds SOtM's sMS-1000 server to this picture, the big PSU becomes a no-brainer. Now it simultaneously powers three devices and in one fell swoop nixes three sucky wall warts and two power cables. In this it mirrors Nagra's new 4-in-1 MPS power supply which can drive up to four of their components. Except that the SOtM will cost a mere fraction of the MPS.

Conclusion. The €3.000 DAC sector is getting awfully crowded. And mature. What your money buys here today makes it most dubious for anyone to advocate spending more unless everything else in your rig had already been dialled to a mirror polish. Where our smart contender from South Korea advances what to expect or get in this class is that it really does replace an analog preamp without excuses.* Going off-grid then wraps that elimination with a bow by making performance independent of utility power vagaries. The sDP-1000 always sounds the same no matter what. Have you gone knackered over your system suddenly sounding lots worse only to mysteriously resurrect days or just a few hours later? Then you'll appreciate if just one component escaped the moody e-morph's clutches. That escape is the primary benefit of battery power. Stable AC-invariant performance.
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*Does that mean a €11.000 preamp of Nagra Jazz caliber belongs on the endangered species list? Nope. At that level of the game there still are fine benefits as I confirmed in a separate session. But those benefits in soundstage layering, depth and dynamic swing cost dearly, aren't that massive and on top of that complexificate everything. Unless you think that's a pretty word, you probably shouldn't go there.


Sonically the DC-coupled sDP-1000 performs on the same level as the Metrum Hex and AURALiC Vega. Not as dry as the Hex, not as glossy or wet as the Vega, it sets up camp between them. Anyone into realsization—the hip concept of getting equivalent or better results from downsizing and simplifying—should welcome SOtM's retirement of the separate preamp. That box is no longer required. That's key. For the low-fat sDP-1000 to be its best only requires an amp/speaker combo which already provides you with 95% of the tone density and image heft you crave. Doing this at the low levels I often listen to, the Vega's digital volume gets lean and lossy. The Hex has no variable output of any sort. If I were to simplify my hifi life, stick with the sound quality I've grown accustomed to from owning the Hex and Vega and not suddenly played a very different money game, the SOtM sDP-1000 really would be my first choice!
SOtM website