Further Analysis: the Gustard X16 and Stellar GainCell DACs, and is Roon Really All That?

Further Analysis: the Gustard X16 and Stellar GainCell DACs, and is Roon Really All That?

Written by Tom Gibbs

In Copper Issue 150, I shared my review of the Gustard X16 digital-to-analog converter as used in my main audio system, and the results were nothing less than spectacular. My intent was to next focus on the X16 in a much less costly system like one that might include the AudioEngine HD4 powered loudspeakers I reviewed in Copper Issue 149. Just to bring everyone up to speed, I’ve been contemplating seriously downsizing my large-scale audio system for a more manageable one, which might be necessary due to possible upcoming lifestyle changes. Or maybe because I might just be ready to chuck it all, and fully embrace my impending retirement in sixteen months with a much less costly and less elaborate audio system.

However, my ever-evolving circumstances ended up temporarily shelving my good intentions. When the X16 arrived mid-November, my main system had been down since early August. That’s because my PS Audio Stellar GainCell DAC/Preamplifier (SGCD) had been at the manufacturer for repairs, waiting for a new main circuit board. Without it, I didn’t have a preamplifier or a high-resolution DAC, which made it almost impossible to do anything other than spin LPs with my PrimaLuna tube integrated amp inserted into my playback chain. But when the repaired SGCD magically appeared a day after the arrival of the X16, that created a crush on my part to complete my review of the Euphony Audio Summus Endpoint streamer. The review was already in progress, but had been seriously delayed while my system was down. Now that I was suddenly back up and running, it was imperative that I focus my attention on this long-overdue review. Pretty much simultaneously, I was immersed in the Euphony review, the Gustard X16 review, and in determining whether the renewed SGCD was actually functioning normally. Added to all that, my daughter was about to give birth any day, which meant that my wife and I might have to drop everything at a moment’s notice to care for my three-year-old grandson (he’s a bruiser!), two dogs, and a pair of guinea pigs. I had a challenging November-into-December, to say the least!

The dual-unit Euphony Summus Server and Endpoint offer remarkably refined digital music streaming.
With regard to the Euphony Summus Endpoint streamer review: my contact at Euphony Audio, Dalibor Kasac, has always insisted that Euphony’s own streaming music player application, Stylus, possesses a remarkable degree of musicality, transparency, and detail retrieval. However, in today’s audiophile world, the Roon suite of music software has become de rigueur in high-end digital systems for music playing and library organization. Despite his enthusiasm for Stylus, Dalibor is a very practical man, so he understands the importance of having his equipment play nicely with industry standard applications that many audiophiles have fully embraced – like Roon. The Euphony Summus equipment arrives from the manufacturer with a Roon core built in, and Dalibor had requested that my upcoming review of the Summus Endpoint highlight the seamless nature of its interaction with Roon. And I’m certain my review accomplished that, while also remaining objective about the quality of Euphony’s own turnkey software solutions. So, for months, I’d been deeply focused on how the Euphony equipment interacted with Roon, and had been listening with Roon almost exclusively. But near the end of the review period, I returned to Euphony’s own Stylus player, and was pretty astonished by the contrast in sound quality between Roon and Stylus. I also did some serious listening comparisons between the Gustard X16 and my own Stellar GainCell DAC, in combination with the Euphony Summus equipment. More on that later. I’ll start with a bit of a continued exploration with the Gustard X16 that was inspired by several exchanges I had with Copper contributing editor David Snyder.
Oversampling Options With the X16

Some additional information about the X16 was brought to my attention by David. He also has an X16, and kindly shared some of his experiences, including adjustments he made to his playback regimen. Apparently David has access to test equipment (hardware, and/or software), and has taken measurements of the X16 as used in certain conditions. He also uses Roon for library management and music playback. My recent system has been using Roon for library management, and the Euphony OS takes advantage of an HQ Player open source protocol that allows for better integration between the Euphony Summus equipment and Roon. David agreed with my thoughts about the superiority of the NOS (No Over Sampling) mode of the X16, and all my critical listening through the X16 was with the NOS mode enabled for playback. Enabling NOS results in fully-native file playback; otherwise, the X16 employs 8X oversampling with every digital signal you present to it. In David’s experience with the X16, he perceived that during playback of Red Book CD-quality files, the sound he was hearing was a bit dull in the treble area. And his measurements showed that when playing 16/44.1 files with NOS enabled, the high frequencies were significantly rolled off. By using the oversampling functions of either Roon or HQ Player, the new NOS curves were almost perfectly flat, resulting in his perception of greatly improved sound quality both in the frequency and time domains.


I used Roon's DSP function to upsample 44.1 kHz files 4X for use with the Gustard X16.

David also uses Roon to upsample PCM sources prior to sending the signal to the DAC; with Roon, you use the DSP function to upsample the signal by whatever modifier you choose. That would typically be 4X-oversampling, or perhaps 8X-oversampling; it’s up to you to decide which you think sounds better to your ears. In my system, since I’m not actually using a full version of HQ Player, I have no access to any of HQ Player’s oversampling options, so I must rely on Roon’s DSP options. They are surprisingly robust, although I’ve heard a lot of people grumble about possible negative results when using Roon’s DSP. I did play about with using Roon to convert everything to DSD several years ago (when I got my first DSD-enabled PS Audio DAC), but I was honestly less than impressed with the results, and have avoided Roon’s DSP with anything since. But I followed David’s instructions, and used Roon’s DSP to increase the sample-rate of my Red Book CD rips and downloads by 4X, while leaving everything else, including higher-resolution PCM, DSD, and DXD at their default (native) playback settings. With 4X oversampling engaged through Roon, I heard a significant amount of high-frequency sparkle in the sound that was previously absent. Now, I’m not a measurements first kind of guy, so I can’t quantify whether what I was hearing was an actual improvement in the sound or not. I didn’t hate it, but I wasn’t certain my ears were telling me that it sounded more correct than playback without upsampling.


Roon's excellent GUI provides tons of information about the provenance of the files you're streaming, and whether any upsampling is being employed. Roon's excellent GUI provides tons of information about the provenance of the files you're streaming, and whether any upsampling is being employed.

In my home system, most of my listening is done with my Magneplanar LRS quasi-ribbon loudspeakers, which can tend to sound, perhaps, a bit bright with certain material. My other go-to loudspeakers, the Zu Audio Omens, use compression drivers in what is essentially a treble horn arrangement, and they also tend to sound a bit bright. So, there’s that dynamic I must deal with in trying to make an objective decision on how oversampling might be affecting what I’m hearing through the Gustard X16. That tendency towards brightness of both of my loudspeaker choices might be impacting what I’m hearing with oversampling engaged in Roon when played through the X16. I might feel (or hear) differently if the oversampling was done by HQ Player rather than Roon, but I don’t currently have full access, so for now, it’s a moot point. I plan on doing more serious listening in the near future, and try to reach some sort of consensus on how I feel about using oversampling with Roon and the X16.


MQA via the USB input With the X16

One of the aspects I listed as a negative for me personally with the X16 was the lack of full Master Quality Authenticated (MQA) decoding via the I²S input, which is my preferred digital input in my home system. Full MQA decoding is only possible via the X16’s USB input. However, I also mentioned that I’m still on the fence regarding MQA, so it was ultimately not a dealbreaker for me. However, should I actually go through with serious system downsizing, the level of equipment occupying my system would most likely preclude anything with an I²S connection. So, a good USB connection would very likely become the input du jour for any given situation in my new reality.


Roon's integration of Tidal makes it really easy to access Tidal's now-vast library of MQA titles

While I was taking the time to explore oversampling via Roon, I thought it might be instructive to take a listen to some MQA titles with the X16, which is made easy by Roon’s built-in access to Tidal. After switching everything in the Euphony System to the Gustard’s USB protocol, I proceeded to sample from a number of MQA offerings. The available selection of MQA titles has recently exploded on Tidal – there’s a boatload of both mainstream and obscure albums across many musical genres. I mostly chose albums I’m very familiar with in either strictly CD-quality versions or higher-resolution PCM versions. I won’t go into detail here, but right out of the gate, 1) I wasn’t completely blown away by any MQA titles I listened to, and 2) I sensed that something in the overall sound quality wasn’t quite right – I can’t put my finger on it, but it didn’t sound completely natural to me. This is going to require much more exploration in the very near future, but suffice it to say, for now, I’m still on the fence regarding MQA.


Making Comparisons With my Renewed SGCD and the Gustard X16

In my initial listening tests with the X16, I have to admit, I was blown away by the sound quality. I still am – I think it’s a remarkable piece of kit, especially at its low $499 USD price point. But in the last week or so, as part of the ongoing review with the Euphony equipment, I’ve taken a really hard listen to the recently-returned Stellar GainCell DAC. And I’ll be darned if it isn’t sounding better than ever! On paper, the Gustard X16 has a vastly superior complement of top-of-the-line 2-channel ESS Sabre ES9068AS DAC chips, compared to the specified ESS Sabre 9010 DAC chips in the SGCD. The 9010s are near the bottom of the line, although they match most of the specified capabilities (with the exception of MQA decoding) of the 9068 chips within certain tolerances. PS Audio’s philosophy is that the DAC chips are only a part of the overall picture, and the SGCD has been voiced to provide a significant amount of trickle-down sound quality and goodness from their much more expensive DirectStream family of DACs. After my four-plus years with the SGCD, I can’t argue with that assessment. And the renewed SGCD is sounding better than ever!


The Stellar GainCell DAC and the Gustard X16 both offer superb sound quality.

Now, this is just entirely speculation on my part, and I haven’t gotten a definitive answer from PS Audio yet, but at the time when the SGCD was there awaiting a new circuit board, it wasn’t alone. I was told that there were multiple units waiting for boards, which were in short supply due to the pandemic. I was offered the option – which they didn’t really recommend – of getting a repair of the existing board. That would have involved basically stripping elements from the existing board to isolate the problem, then replacing them with new parts in an attempt to restore the board to its previous condition. My alternative was to wait for a fully-assembled replacement board, which was definitely my first choice. And after hearing such a marked improvement in the sound quality of my renewed SGCD, I’m beginning to wonder if perhaps my new board came equipped with an upgraded ESS DAC chipset – or possible other improvements.

I plan on removing the outer cover to examine the board and check that out soon, I just didn’t want to go through the hassle of doing it prior to the publication of this article. I’ll update the results of my explorations in an upcoming issue. My initial listening experiences with the Gustard X16 were superb, and my opinion of it hasn’t changed at all – it’s an astonishingly good DAC at any price, and especially at its ridiculously low price. But my recent listening to the SGCD has also altered my opinion of it; it’s a much better sounding DAC than I might have previously given it credit for. I actually think the X16 and the SGCD share many more similarities than differences – especially when both are connected via the excellent I²S connection.


The Euphony Summus Endpoint has elevated my enjoyment of digital music to a much higher level.

My Euphony Review, and Changes to my Ongoing Implementation of Roon I’ve been using Roon on and off for over five years now, and for about the first three years, I was given a complimentary reviewer’s subscription. That was a godsend at that point in time, because I was then constantly trying to cobble together a digital file streaming system from DLNA and UPnP open source applications, which were often buggy and frustrating to use. Even with really superb streaming equipment like the Sonore Rendu line of streamers, trying to use freeware to get glitch-free, bit-perfect streaming was quite simply maddening, to say the least! Roon worked, plain and simple, and it sounded better than anything else I had access to at the time. When my reviewer’s subscription ended, I chose to continue to pay the $12 monthly fee – partially, because I was still pretty high on Roon, and I really loved their file management. But also, as an audiophile reviewer, it’s pretty much expected of me to have access to industry-standard music software for many of the reviews I engage in.


Roon's GUI is the slickest in the industry.

As part of the Euphony review (you can read that here), I suspended my use of Roon and started using Euphony’s own Stylus application again for the first time in months. Stylus handles the library organization and music playing aspects of the Euphony system that an outboard program like Roon might otherwise have managed. Stylus has an acceptably good graphical user interface (GUI), and really good functionality as a music server and library organizer, if perhaps not possessing the same level of refinement as Roon, especially in terms of visual appeal. But after spending the last few weeks listening to digital files over the Euphony system via Stylus – and that’s whether with the X16 or the SGCD – it’s become abundantly clear to me how much better Euphony Stylus sounds in this implementation. Stylus gives loads of air, delicacy, transparency, and simply gobs of detail. Whereas, any of the Euphony modes featuring Roon sounded, quite simply, somewhat pedestrian, relatively lifeless, and more mid-fi – especially in comparison to Stylus. The Euphony Stylus playback mode utilizes a "ramroot" function that allows the user to insert the files selected for playback into the Summus Server's RAM cache, which is massive at 16 GB. The files are then spooled directly from the Server's RAM to the Endpoint streamer, which results in the files being played with zero latency. This essentially means that there's no appreciable transfer function lag that might otherwise be encountered by playback from disk storage to the Endpoint. I know that some may scoff that any appreciable improvement in sound quality could be offered by this arrangement, but the proof is readily apparent during playback. It’s much more nuanced, detailed, and musical than anything I'm hearing from Roon; Stylus definitely has a technological edge in terms of playback sound quality over Roon.


The Stylus GUI might not match Roon's level of sophistication, but its functionality is excellent.

I’m definitely at a crossroads with all this; whether or not I decide to continue to remain heavily involved as an audio reviewer will probably determine whether I keep my Roon subscription or not. At this moment, I could probably walk away from it with no regrets. Maybe it’s time I caved and dropped the bucks for that full HQ Player license – but then, if I downsize drastically, that money would probably be wasted!


Finneas has finally arrived!

By the way, my new grandson, Finneas, arrived December 10th (he’s great!), and the five days I spent away from my system gave me even more time to contemplate walking away from it all. After days on end of being Hulk-hammered senseless by my Marvel-Universe-loving three-year-old grandson Henry, and being constantly nuzzled by needy dogs, do I need the headaches of the high-end?

All images courtesy of Gustard, PS Audio, Euphony Audio and the author.

Header image: Gustard X16 DAC.

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