Soulnote D-2 DAC
Soulnote is Japanese brand that has been around for a lot longer than recent events would suggest. They first made an impact on me at the High End show, Munich in 2022 but a quick web search reveals that their products go back considerably further, to 2004 in fact when it was founded by former Marantz employees. The brand had a change of approach in 2016 when Hideki Kato became Chief Sound Manager, this was when the current range started its development. The offering now consists of three series with Series 1 being the entry level and Series 3 the flagship, which puts the D-2 DAC in the middle with a price that is around a third of that asked for the D-3. The other Series 2 components are the A-2 integrated amplifier and E-2 phono equalizer, only Series 3 contains a wider range of components including pre/power amps and a streamer.
What pricked my interest at that High End show was that loudspeaker guru Karl-Heinz Fink was using Soulnote electronics to launch the Epos ES-14n loudspeaker, he usually has a good ear for electronics and both his system and Soulnote’s own sounded particularly good at that event.
Soulnote is an interesting company, bigger than the majority of those in the high end but not in the mainstream league it is able to build products like the D-2 at what is a competitive price for a Japanese DAC with high build quality and cutting edge tech. It can do this because it has the benefits of scale rarely found in this sector. At 17 kilos the D-2 is as substantial as many integrated amplifiers at this price, not that mass equates to quality but it usually equates to higher prices. It’s also a superbly executed piece of kit with more features than most, some of which can be confusing nuisance, but more of that later. You only have to look at the open lid shot to realise how much more there is in this DAC than usual; it doesn’t just weigh as much as an amplifier it has the sort of power supply usually found in an amplifier.
Unusual choices in the parts department include a Texas Instruments LMX2594 synthesizer rather than a standard DDS (direct digital synthesizer) because it provides far lower jitter of 45 femtoseconds. While the internal clock “boasts stunning [ly low] phase noise” there is the option of adding a separate 10MHz word clock to the D-2, and doing so turns off the internal clock power supply which further enhances performance. I tried this with a third party clock and can confirm that it is indeed highly beneficial.
The digital to analogue converter within the Soulnote D-2 consists of four ESS ES9038PRO DAC chips used in a differential arrangement with two per channel creating a true balanced output. These are coupled with a discrete amplification output stage that is free of negative feedback and allows for “extremely simple” IV circuits (the current to voltage conversion that exists in every DAC). Soulnote are very keen on NOS or non-oversampling digital filters because, as others have observed, such filters deliver better timing because they don’t have the pre- and post-impulse echo or ringing that is found in typical oversampling filters. NOS DACs are made by a few companies but tend to be in the minority, largely, one suspects, because the big numbers quoted for oversampling systems look so impressive, and these can also sound very good of course.
Soulnote go to considerable lengths to eliminate noise wherever possible in the D-2, for instance they wrap the circuit boards in copper foil; the differential amplifiers mentioned above are arranged dual-mono style in order to isolate the two channels; and connecting cables have been eliminated wherever possible in order to reduce the potential for noise pick up. The reason that the D-2 looks and feels like an amplifier is that it uses a 400 VA toroidal transformer as the basis for its power supplies, such transformers are typically used in amps rather than source components like this. They minimise mechanical noise by fixing the transformer to the third foot (for which a spike is supplied) at the front of the box.
Another unusual feature is that the grilles that are inset into the case top are not fully fixed but rattle if tapped, this is because Soulnote believe in decoupling rather than damping when it comes to combatting the problems associated with metal casework. They are the only company in my experience to suggest that enclosures change the sound but others have clearly discovered as much, the existence of acrylic and wooden cases being clear attempts to deal with the problems associated with metal boxes. It’s worth reading Soulnote’s philosophy on this, they have clearly done a lot of work in this and other rarely considered areas.
Connections
The D-2 has more sockets and switches on its behind than most converters I have encountered, there are the usual RCA or XLR outputs alongside two lots of AES/EBU and coaxial inputs with USB being the fifth and highest resolution option. It’s the tiny switches that are different, on the periphery are alternative pin settings for XLR/deselecting RCA, and in the middle is a stereo or L/R mono switch so that you can use two D-2 DACs in one system. There are even switches for oversampling settings, FIR 1 or 2, and low pass filtering for DSD. Finally we have the word clock BNC and associated switch. I was twice caught out by accidental knocks to these switches (easily done whilst moving the box about it seems) that left me scratching my head about the change in sound, but they provide a degree of flexibility and upgradability that is rare.
Sound quality
Hooked up to my Longdog Audio power supplied Lumin U2 Mini streamer I used the D-2 in NOS mode exclusively because past experience has taught me that DACs which offer this facility always time best that way. Oversampling adds a degree of finesse that is appealing but doesn’t necessarily make the music as immediate and engaging. The tonal balance is more open and eager than usual albeit with a vaguely tubey quality that stops leading edges from being sharp and brings a shade more richness to tonal shadings. But only a shade, this is not a richly balanced converter it’s a groove machine, so when you put on Lou McDonald’s horn and keyboard powered One Cylinder you know all about it, and that’s mainly because your leg won’t sit still, nor your head. In this instance the drums and guitar are forward of the organ, and the horns have an immediacy that is gripping.
I came across a track called Chains (William S Fisher) on one of the Late Night Tales compilations (Floating Points), this is a slow burn piece that can easily pass you by but here the build was more obvious and the crescendo particularly rewarding. The Soulnote D-2 clearly has a good handle on small scale dynamics, it tracks the way that instruments and voices change in volume and their relationship to the mix as a whole rather better than most. It has a leanness of tonal balance that is more obvious with some tracks than others so I experimented with USB cables, switching from the warts and all muon2 to CAD USB II-R which is a little more forgiving, and this enriched the tone rather nicely. Ali Farka Toure’s Ai Du (Talking Timbuktu) delivering its lovely lilting groove, body and slam in unusually clean fashion, Ry Cooder’s steel strings really zinging and the mandolin playing standing out to entertaining effect.
There is no thickener in the D-2’s balance, no smoothing to mask the signal and this makes it less forgiving of heavily compressed or overly ‘hot’ recordings but put on something well put together and you get the undiluted energy from the studio or stage. One example I tried was Bermuda Blues by the Henry Threadgill Sextett (You Know The Number), this is a two drummer, multi horn blast that can easily spill into raucousness, the Soulnote delivers that raw power but keeps everything coherent so that it doesn’t sound screechy or ‘loud’. This is largely down to timing, many sources sound aggressive because of timing problems rather than an intrinsic tonal imbalance, the D-2 is clearly not among that number. It is also very capable when it comes to reproducing space and reverb, the production on Triage by Erik Honoré helps in this respect but I have not encountered sounds moving around the room to this degree before, it’s quite uncanny.
I also combined the D-2 with a Mutec Ref10 Nano clock just to see what benefit that would accrue. Clocks don’t always have a significant effect in my experience and this is a relatively affordable example of the breed, yet the change was not subtle. The depth of image gained in three dimensionality by a significant margin and it wasn’t shabby to begin with. Likewise timing which is a clear strongpoint went up a few notches and made Massive Attack’s Protection far more rounded and involving. Colour of the Rain by Oisin Leech (Cold Sea) is a fairly simple voice and guitar production but the Soulnote brings out depth that is do die for, it feels like you’re in the presence of a living, breathing musician, albeit one who has better sound than most achieve in the flesh. The more music I played the better this pairing sounded, clearly what Soulnote have done to take the internal clock out of the equation when an external one is used is helping.
Conclusion
The Soulnote D-2 is an exceptionally good digital to analogue converter, one that truly does bridge the gap between analogue and digital sources. It is superbly built, has features found hardly anywhere else and makes digital streams sound like real music in a way that is rare. Add to this the ability to upgrade it with a word clock and you have a converter that should er, convert, many a digital sceptic.