Cees Ruijtenberg knows digital. Under the Metrum Acoustics banner, he was responsible for such highly regarded DACs as the Octave, Hex and Pavane – designs which I refer to as “keepers” for their tendency to find lasting homes, often in systems which had until then been in steady flux. And while Ruijtenberg has also brought amplifiers and pre-amplifiers to market – quality gear by all accounts – he remains most notable for his NOS R2R DAC products.
This isn’t a review of a Metrum Acoustics product, but rather the Morpheus DAC from Sonnet Digital Audio. Those who don’t follow forum chatter may not yet be up to speed, so I’ll give a quick recap on the situation before we move forward: an outside investor came on board with Metrum, which led to some conflict and customer service issues, and eventually resulted in Ruijtenberg moving on to form a new company called Sonnet Digital Audio. Metrum soon thereafter went bankrupt and, one way or another, Ruijtenberg was able to regain control, putting him and us back at square one – with the minor wrinkle of Ruijtenberg having a second lineup of gear under the Sonnet banner. How he intends to differentiate the two remains to be seen, but both are slated to move forward with upcoming products.
Having established the back story, let’s talk Morpheus.
Design and Functionality
The US$3399 D/A conveter uses a quartet of Ruijtenberg’s proprietary SDA-2 ladder DAC modules (two per channel) stitched together by custom code running on an FPGA. Each SDA-2 module actually contains four internal resistor ladders, putting the cumulative total at sixteen; or twice that of previous flagship designs from Metrum. Going beyond strict D-to-A duties, the Morpheus also sports volume adjustment by way of variable voltage straight from the DAC chips themselves rather than digital attenuation. This results in a true lossless output and provides a compelling argument for feeding your amplifier of choice directly – though I’m sure Cees would prefer that amplifier to be one of his designs.
The feature set is respectable if not quite mind-blowing. Upfront, simplicity rules the day. Morpheus has two buttons (source and power) plus a single rotary knob for volume control which can be pressed for mute. A simple display gives us the basics in a straight-ahead fashion without much concern for wiz-bang aesthetics. I find it perfectly adequate if not as fashionable as some others. On the other hand, the stylish remote control has that all-metal “audiophile heft” yet still manages to be quite intuitive to use – not something every brand can pull off.
Analog outputs come in both single-ended RCA and balanced XLR flavors. Standard digital inputs are optical, RCA, and AES, with the fourth spot being modular. Most users will likely opt for the USB input, but Sonnet also has an I2S option (for no additional charge) which I would highly recommend. It uses an RJ45 format rather than the somewhat more common I2S over HDMI (favored by PS Audio, Wyred4Sound, etc) and is thus intended for use with the matching Sonnet Hermes streaming player. Beyond that, we get a set of power trigger connectors, useful when integrating the matching Kratos monoblock amplifiers into a Sonnet-oriented system.
The modular theme extends further into Sonnet’s design language. The Morpheus’ SDA-2 modules can be replaced if/when Cees comes up with a next-gen solution. This has been a hallmark of his philosophy since the earlier Metrum days. We also get the ability to add an optional MQA card which gives interested parties full MQA support without forcing all buyers to subsidize that niche format.
Whilst we’re talking niche appeal: as with DACs from Schiit Audio and Metrum Acoustics, the Sonnet’s Morpheus does not handle DSD playback. At all. That may sound shocking for a modern device, and stands in stark contrast to most competitors which commonly offer support for DSD256, DSD512 and beyond. When I consider the vanishingly small amount of actual content available in DSD, and then filter out music that doesn’t really appeal to me, I don’t consider this a huge loss – but some readers certainly might. For those folks, Roon does a very credible job of converting DSD to hi-res PCM (which the Morpheus can handle, up to 24-bit/192KHz), losing very little fidelity along the way. But it’s still something for readers to take into consideration based on their music library and preferences.
Cees Ruijtenberg kindly sent over the matching Sonnet Hermes network streamer (US$1199) to be used in tandem with the Morpheus. The Hermes works as a Roon endpoint, pulling music from my Euphony Summus (US$3300 with PSU upgrade) running in Roon server mode. I also compared the Hermes to the Nativ Vita (US$2200) which also acts as a Roon endpoint. Monitoring came by way of the ravishingly transparent Stax SR-009 electrostatic “earspeakers” (US$3825) being fed by a prototype version of the new Corsonus Kodachi amplifier (US$3600). I also switched over to the Cayin HA-6A (US$2499) for a second opinion, driving various headphones including the Kennerton Thekk (US$3299) and Audeze LCD-24 Limited Edition (US$3500). Audio Art (who happens to be an authorized Sonnet dealer for North America) supplied their power1 ePlus AC cables as well as SE2 interconnects and digital cables, and the whole rig was fed balanced power from an Equi=Core 1800 (US$2199) line conditioner.
I’ll admit to having entered this assignment a little biased towards the Morpheus. First, it’s a Non-Oversampling design. While not true in every case, NOS DACs have generally earned the reputation of sounding lush, rich, and sometimes a little darker than delta-sigma implementations. However, these designs aren’t usually the first choice one seeks when chasing ‘high pixel count’ resolution. Secondly, prior to this project, my chief experience with Ruijtenberg’s designs had been the Metrum Hex (US$3500) and Onyx (US$2500) DACs, both of which did fit the NOS stereotype to some degree. I deliberately chose the extremely revealing Stax/Corsonus duo for the bulk of my listening as I knew the combo would very plainly show any such colorations.
Digging into Wolfgang Muthspiel’s Where The River Goes in 24-bit/88.2KHz courtesy of Qobuz, I was not greeted by the expected lush/rich tonality at all. Instead, Morpheus gave an airy, open presentation with a surprisingly vivid display of low-level resolution. Not to be confused with a lean, tipped-up signature (incisive detail retrieval doesn’t always equate to thin sound), I’d call it very well-balanced and even-handed, which, again, is not the way NOS DACs are typically described, even by their most vocal proponents. Here was a more universally appealing presentation, one which would sit well in most any system.
I then switched to The Gleaners by Larry Grenadier, who had provided double bass on the previously mentioned Muthspiel release. This is one of my favorites for testing tonal richness – many components just fall flat when tasked with reproducing the heft and body of the largest member of the string family. But not the Morpheus. In a suitably capable system, it unleashes a reach-out-and-grab-it picture of the big wood instrument. And it does so without artificial enhancement or overcooked warmth. The Morpheus also feels fast enough to reproduce the intricacies of Grenadier’s masterful playing. Other high-quality DACs can give the illusion that they are teasing out one aspect or the other, but it’s not so common to find one equally capable in both fullness and articulation.
It was then that I locked onto the larger-than-average sonic landscape painted by the Morpheus. NOS DACs I’ve owned or auditioned in the past tended to be generally underwhelming in this particular area. Even the Metrum devices, which I felt were better than most NOS alternatives, weren’t particularly noteworthy compared to their more “traditional” competitors. Morpheus felt different – more open, fluid, unobstructed. This finding came via more predictable audiophile fare (Pink Floyd and Count Basie and Amber Rubarth etc) but also some unexpected selections from Yosi Horikawa and Social Distortion’s Live At The Roxy. These albums (and more) left me with the impression that the Morpheus could lay out a large stage ready for its more precise imaging skills, thus approaching the very best I’ve heard from any DAC in my rig. I had certainly not expected this from a NOS design.
While focusing on the DAC’s specificity, a broader quality made itself known to me. I realized I had been listening at higher volume settings than usual. The clean, unforced presentation, utterly composed and free of treble glare, had me goosing the volume knob without even noticing. Over the years I’ve learned that I’m generally more of a low-volume listener compared to most folks, and I usually only find myself cranking the volume when trying to reclaim some lost dynamic impact from a reticent component (an endeavor which typically proves futile). That was certainly not the case here though. The Morpheus gave such a poised, confident performance that it practically demanded higher levels so I could hear more of what it had to offer.
It was at this point that I moved out the electrostatic gear in favour of the Cayin HA-6A tube amplifier driving various planar magnetic headphones. In all cases I got a very pleasing if slightly less transparent result – it’s hard to match Stax in that aspect. I was again struck by the Morpheus’ tendency to play it straight down the middle – without sounding the least bit analytical or sterile – and how it excelled with a variety of differently-voiced headphone options. From the muscular Meze Empyrean to the ethereal Kennerton Thekk to the protean Audeze LCD-24 Limited, the Morpheus has universal appeal sewn up. It’s full-bodied, open, extended, and very dynamic, yet not solely defined by any one of those attributes.
Prior to Morpheus, I had been running the same Stax system with Chord’s Hugo TT2, in what must be at least my fourth attempt to enjoy that particular DAC. While admittedly doing certain things extremely well, the TT2 lacked the Sonnet’s audible agreeability. The contrast was quite easy to hear and can be summarized by the fact that I often found myself turning the volume down when using the Chord device. Even after establishing a comfortable setting, dynamic peaks could often feel so sharp as to offend the ears. Switching to the Morpheus was a welcome relief that didn’t merely temper that sharpness but completely fixed it on a fundamental level – increased quality rather than diminished quantity. Beyond that I found the Morpheus to be more convincing with music’s timbre, whereas the TT2 lent certain instruments an artificial aftertaste. Swapping the electrostatic setup for the Cayin plus Meze combo made a more copacetic pairing with Chord’s device, but my preference remains firmly with the more natural and texturally pleasing Morpheus.
A more worthy challenger would be my Oppo UDP-205 with extensive upgrades made by Dan (Mod)Wright Instruments. In stock form the Sabre-equipped Oppo is a detail monster but its overall presentation lacks a bit of weight. Dan Wright’s treatment, complete with a quad of Lundahl transformers, reworked and tube-augmented output stage, and a massive tube-rectified outboard PSU, turns up the tactility factor to eleven. Paired with an embarrassingly costly pair of Valvo CCa tubes from the late 1950’s and a Philips 5R4GYS rectifier tube recommended by Wright himself, this enhanced 205 sounds like Morpheus’ bigger, bolder sibling – a sibling who should, once in a while, hit the library instead of the gym. It gives us increased fluidity, richer tonal colors, and more obvious saturation, in exchange for some top-end delicacy and overall nuance. The ModWright Oppo is voiced closer to what I recall from Metrum’s flagship Pavane Level 3, which I believe went for about double the price of the Morpheus. Factoring in these expensive tubes puts the ModWright in that same ballpark as well, making Sonnet’s latest converter a relative bargain when we note just how well it plays in the same league. I’m honestly not sure I would peg one as better than the other – it comes down to system matching and mood as much as actual sonic performance. Alas, Oppo’s exit from the audio/video market has seen the UDP-205 going for absurd prices second hand (to say nothing of those Valvo tubes) which makes recreating this machine far more costly than it was a few years ago. The Sonnet Morpheus is the far more affordable and accessible choice, likely to synergize nicely in a greater number of systems.
Thoughts on Hermes
While this is primarily a review of the Morpheus DAC, I do feel it useful to mention the matching Hermes transport (US$1199) which Sonnet refers to as an “advanced network streamer”. Using an internal Raspberry Pi 4 for data processing, the Hermes builds upon the Pi architecture with an all-new, built-from-the-ground-up platform using audio-specific components. This gives users what they need from a quality transport; extremely low noise along with high signal purity. Hermes offers outputs in AES, coaxial, optical, and the Sonnet/Metrum specific I2S format, whilst the sole input is hard-wired Ethernet – no WiFi here.
Hermes is primarily intended for use as a Roon bridge. The instructions do make mention of the rear-panel SD-card slot which enables users to roll their own OS, but further details aren’t readily given. Methinks anything from DietPi to Volumio would be fine choices, but I did not go down either of those paths so I really can’t comment. Besides, Roon is by far my favorite playback solution, so I’m satisfied with Hermes right out of the box.
After pairing Hermes with Morpheus using all available connection types, my clear preference is with the I2S. It makes its case by a clear margin to leave all other inputs asking “how close to I2S can we get?”. AES comes the closest, followed by coaxial, and then TOSLINK. It’s not that they sound “bad” but rather that I2S is just so good, and since my Morpheus review unit has the corresponding input, it makes sense to stick with the superior transmission method.
Comparing the Hermes to the Nativ Vita music server/streamer (also running as a Roon bridge) means we have to put I2S to one side. In this A/B, I hear nearly identical results when using the same connection type to feed the Morpheus. Which is to say; both devices make superb transports. AES is particularly satisfying in both cases, though coaxial and TOSLINK are both quite capable as well. Vita and Hermes are focused very differently, so with sound being equal, it would come down to pricing, features, and form factor…until we recall the Hermes I2S’s advantage. With that connection in play, the Hermes gives better fluidity and superior illumination of instruments and the spaces in between. Image specificity is clicked up a notch. As much as I love the Vita and the tactile experience offered by its 11.6″ touchscreen, the Hermes via I2S just takes things further in terms of fidelity.
Conspicuously missing from Hermes is a USB output. With Morpheus’ standard configuration being USB rather than I2S, is that an oversight? I’d argue not. For starters, the chief benefit of USB typically revolves around DSD support, where most other devices are stuck at either single-rate DSD64 or no DSD at all via their “legacy” inputs. Since Sonnet’s devices omit DSD playback altogether, the issue becomes moot.
More importantly, I just don’t feel the Morpheus’ USB input is all that great. It has a somewhat homogenized feel to it, lacking the separation and texture I hear from the other inputs. I would sympathize with this sort of result when using a basic laptop or NUC as transport, given their general-purpose designs and associated electrically noisy outputs, but to get this same impression when using the Nativ Vita, Cayin iDAP-6, or Euphony Summus – all high-class USB transports – tells us the transport isn’t to blame. I even tried tweaks like the iFi iPurifier3 and BMC PureUSB but with no significant improvement.
My recommendation for Morpheus buyers is to grab the (free) I2S option instead, even if you won’t initially be using the matching Hermes transport. Those who rely on USB output and don’t have options for alternatives should look to digital-to-digital converters. I like the Matrix X-SPDIF II but there are many other worthy choices. These convert USB to AES/coax/optical to bring audible improvements (over the Morpheus’ USB input) to the table. Those users could later grab a Hermes for additional sonic gains via I2S.
I’ve already mentioned my initial bias going into this review, and how thoroughly wrong it ended up being. This non-oversampling, R2R DAC design is wonderfully balanced and in a way that I’d not heard from Metrum DACs. The interesting part is that I consider this a good thing; it’s not just a departure of an existing “house sound”, but rather a breakthrough in what can be achieved using the same(ish) technology. Morpheus extends its capabilities for a well-rounded, universally enjoyable device. I happen to know several former owners of the Metrum Pavane (in both original and Level 3 status) who switched to the newer Morpheus and consider it a worthy upgrade — and I can totally understand why. Despite a lower cost (thanks to a more efficient power supply and more utilitarian casework), the Morpheus really does offer more without discarding that Metrum appeal.
It’s no big secret that Cees Ruijtenberg does have another Sonnet DAC in the works, likely shipping before the year is out. As such, it’s tempting to advise prospective Morpheus customers to wait until that drops. Counteracting that temptation is the realisation that the forthcoming Sonnet DAC will sell for nearly double the asking of the Morpheus. That makes it another beast entirely, and probably not appropriate to be cross-shopped with its less expensive sibling. Meanwhile, available at this very moment, the Morpheus offers a staggering level of performance for the price. And that’s not even counting its usage as a pre-amplifier (which my headphone-based systems can’t really utilize). While I’ve always enjoyed the Metrum products, and hope to hear further good things of theirs in the future, I’ll boldly assert that the Sonnet Morpheus is the most significant DAC Cees Ruijtenberg has brought us to date.
Further information: Sonnet