review by Andrew Ballew (Click here for DAC specifications) When the S.M.S.L D400 PRO DAC arrived here seemingly an eternity ago, I was quite excited to hear a different implementation of the latest state-of-the-art AKM dual chip AK4191+AK4499EX DAC silicon. I had first encountered it in the Topping E70V Velvet DAC, and was intrigued by its potential. Something wasn’t quite right with the sound though. (Click here for that review.) Overall it sounded very, very good, but there was a slight graininess in the sound that didn’t sit well with me, that wasn’t present in other AKM implementations I have heard. At the time of review I chalked it up to being over-revealing. Also, the Topping (despite what some well-known online reviewers claimed) did NOT take advantage of the native DSD ‘Bypass’ mode. Bypass does more than just fix the volume control at 100 percent; it bypasses the delta-sigma converter altogether and uses the output switches as a 1-bit (DSD) FIR output filter. It is a digital filter realized by analog means(sort of a digital/analog hybrid) with shift registers and resistors, operating in unary code as a simple “moving average” filter. Previous AKM implementations of native ‘Bypass’ mode have sounded quite good. I wanted the chance to hear it as implemented in their latest and greatest chip, which moved from switched capacitor filters to resistor-based filters. Little did I know exactly what was in it for me- that seeming eternity of measuring and reviewing. Starting with the basics, the D400 PRO arrives as a well-built piece of kit. It is solidly put together, its display is quite crisp and of high quality. It is easy to use and the controls feel solid. The remote is the same generic remote I have seen with other S.M.S.L products. It does the job, and that is really all that can be or need be said about it. Some months earlier when I reviewed the S.M.S.L D300 I was stunned by how cheaply that DAC was constructed. (Click here for review.) No such issues with the D400 PRO. It is a properly built component as I would expect for its price. To evaluate the D400 PRO, I paired it with two different headphone amps, those being the iFi ZEN Can, and the S.M.S.L SP400. Headphones used in the evaluation were my trusty Sennheiser HD650, the Hifiman HE-560, and the Focal Clear MG Pro edition. Software for playback was Roon via standard windows PC. The DAC was galvanically isolated from the PC at all times via the Intona USB 3.0 SuperSpeed Isolator. The DAC was always evaluated via the balanced outputs, and all cabling from USB to XLR consisted of a variety, mostly from AudioQuest and WireWorld. I began my evaluation of the DAC with the Elgar Cello Concerto in E minor Op. 85 via TIDAL (16bit 44.1k PCM). Alisa Weilerstein, performing with Staatskapelle Berline under the baton of Daniel Barenboim, shows absolute mastery of the Adagio-Moderato opening movement, with breathtaking subtle musical movements of what might be the most beautiful Cello melody ever written. The incredible technical dynamic range of the S.M.S.L D400 PRO powered by the latest AKM chip really allows the finest of low level details to become present, offering up a stunningly ethereal, nearly live sounding performance. Fine details float in space both left and right, making me forget for a moment I am listening via Sennheiser HD650 headphones, briefly fooling my ears that I am listening via my reference Martin-Logan ESL speakers. Yet no crosstalk is turned on in the digital realm; neither is the iFi ZEN Can being used with any of its onboard analog signal processing active. Very impressive. Unfortunately as beautiful as the S.M.S.L resolution is a low levels, things begin to sound more flat and compressed at higher volume levels. All evaluation to this point had been with the ‘Low Dispersion’ filter. For the "fun of it" I listened to the same sample of music with every available PCM filter. In ‘Super Slow’ (non-oversampling), the cello tones and overtones sounded quite glorious. Even a bit more engaging than the ‘Low Dispersion’ filter. However, the background took on a bit of graininess and the deep pure black experienced in ‘Low Dispersion’ was no longer present. Once again, louder passages sound much less tonally controlled and retreat a bit from the strong stereo imaging. After much mind-numbing comparison, I decided the most balanced filter that provided excellent low-end control along with high-mid to treble sparkle and “freedom to sing” was the ‘Short-Slow’ filter, which is a low tap minimum phase filter. You will find this kind of filter used on MQA material. Note, I am not suggesting this is the MQA filter; only that its impulse response looks similar. Cursory looks can be deceiving. The bottom line is, by some margin this is the favorite D400 filter evaluated at Euphonic Review. Unfortunately, even the most optimal filtering cannot overcome the slightly flat, spatially indistinct sound at higher volume levels that seems to be characteristic of the DAC with PCM material, in spite of state-of-the-art measurements. Moving onto MQA, which I personally find to be my favorite delivery format these days, I “virtually” stayed in Berlin, but switched over to the Philharmonic, still under the direction of Daniel Barenboim, for a fine performance of the Allegretto movement in the A Major Beethoven Symphony, Op. 92. For the most part until one reaches the end, this is a low-level, highly detailed masterclass of classical music reproduction. The acoustics of the hall and stage are firmly entrenched and allow one to close their eyes and see in the mind each detail that must be taking place. The imaging is quite astonishing. An individual violin just ever so slightly stands out as out of conformity for a mere microsecond. I was surprised to hear that kind of resolution here. When the viola section begins to sing a melody in one accord, its richness of tone and musicality brought goosebumps. But, just as before, when things got a bit busy at higher output levels, the soundstage flattened, the imaging collapses somewhat, and one is pulled out of the illusion of ‘being there.’ I took a break and cued up “The Ayoub Sisters” self-titled album and was left with a large smile after the track, "Uptown Funk". The percussion here is so subtly detailed and nothing in the mix is missed. Each sister’s virtuosity with their respective instruments Cello and Violin was sharp in a good way and cut through the mix. This was also the first time I felt like the overall dynamics were not compromised. The 24/96 track was very nicely rendered by this DAC. At this time, I felt excited to check out the DAC’s DSD performance; specifically, the 'Bypass' mode that allows for native DSD conversion. The previous iteration I reviewed of the AK4191 + AK4499EX in the Topping E70V ‘Velvet’ did NOT offer access to the DSD ‘Bypass’ mode that allows DSD files to be filtered via the analog FIR filter in the output stage of the AK4499EX. Several review sites errantly equated the fixed volume output feature with this ‘Bypass’ mode. I already was aware of this error, but just to be on the safe side, I personally confirmed with Topping that there was no DSD bypass available on that product. The fact that the S.M.S.L DAC under review here does indeed provide access to this bypass mode was a big, big deal for me personally, as this is how I prefer DSD conversion. ‘Native’ DSD, which I would describe as meaning as little DSP and filtering as possible. In the menu there are three choices under ‘Pre-Mode’, those being ‘Variable’, ‘Fixed’, and ‘Fixed DSD Bypass’. I began my DSD playback reviewing via the 'Bypass' mode with the 'Wide' filter activated. In 'Bypass' mode both 'Narrow' and 'Wide' filters seem to cutoff at around 70khz on DSD64 material. The significant difference between the two is a much slower roll-off in 'Wide' mode. The SACD/DSD album I settled on was “Torme’, A New Album” re-released by Audio Fidelity in 2002 re-mastered by Steve Hoffman. Wow. This was DSD as its best. Just a stunning transfer from the original analog tapes to DSD64 with Hoffman’s legendary touch. On the opening track "Send in the Clowns", the brass cuts through with such a thick, natural wall of sound that one might be tricked into believing they were there during the recording. On the second track "New York State of Mind", Torme’s voice was reproduced with truly stunning harmonics that gave such an open, rich yet light tone that truly must be heard to understand any description. None of the “flatness” I heard with PCM files was present here. It was just an outstanding presentation, and the native DSD 'Bypass' was living up to its billing, sounding like other known native DSD DACs I have here in the lab such as those made by iFi (Burr-Brown), RME (AKM), and Signalyst (32 tap/33 level discrete FIR filter). And right about here, is where things went crazy and why this review took way longer than usual. Going any higher than DSD64 in 'Bypass' mode could be a total disaster of white background noise; or it might not be. Taking measurements was maddeningly inconsistent. I couldn’t put my finger on the problem. And my finger still isn’t completely on the problem. But at least I know I am looking in the right place and these gremlins are on the run. There is a feature (non-defeatable) in the D400 called ‘ND Color’ in the menu structure and ‘Sound Color’ in the user manual. Sound Color is an AKM feature for which I can find no actual technical explanation, other than it is supposed to be some kind of tone control. ESS has something similar, so I suppose this is a case of “keeping up with the Jone’s”. I really felt like I had chased down my problem when I discovered that this feature is implemented in the AK4499EX chip, NOT in the AK4191 chip where the digital modulation is found. The reason this is important is the DSD ‘Bypass’ mode filter is located on the AK4499EX chip, implemented in the shift registers and resistors/switches. Changing the ‘ND/Sound Color’ from default to ANY of the other three choices is STEP ONE in eliminating the issue with native DSD, all the way to DSD512. More guessing and speculation on my part says that the ‘ND/Sound Color’ “feature” is affecting the sound at the analog output itself, and while it may work just fine for Multi-bit Delta Sigma delivered from the AK4191, it is causing problems with the output filter in 1-bit mode. Whatever the case may be, the problem seemed to be solved by changing the ‘Sound Color’. At least to the point of inaudibility. Unfortunately, a month of measurements documenting the noise issue with DSD are now useless. Time would have been better spent measuring exactly how each of ‘Sound Color’ modes affects the signal. I will provide this later as an addendum to this review. But what about STEP 2?? I thought the problem was solved? Oh no, not just yet. Your choice of “Sound Color” will interact with your choice of either 'Narrow' or 'Wide' filter, for better or worse. This further seems to confirm my hypothesis that the ‘Sound Color’ feature, while working fine with Multi-Bit Delta Sigma content, when presented with 1-bit content, works havoc on the analog filter now configured for DSD. What I WILL say about DSD via the ‘Bypass’ mode- once sorted out- sounds amazing. I will also say it is an absolute shame that anyone would have to go through this bug-ridden mess to find that amazing sound. It is some of the very best DSD sound I have ever heard, and coming from an approximately $650 product, is saying something. Again, that endorsement is for the 'Bypass' mode when you have sorted the gremlins. DSD via the DSP/remodulation route sounds very much like PCM as I initially described-excellent low level performance and detail, but a bit flat and lacking in high level dynamics. However, with DSD via 'Bypass', in its simplest conversion mode, the sound approaches if not matches the very best I have heard, no matter what the measurements say or will eventually say. Further thoughts? When all the bugs are worked around, DSD played back via the ‘Bypass’ mode sounds so good (regardless of whatever the measurements may show when I have the chance to remeasure and share) that for a time I considered placing the D400 in my primary headphone system so I could move my current reference headphone DAC, the iFi iDSD PRO to my new reference speaker system. But even still I can’t help but be so annoyed by the truly unacceptable bugs that had me pulling out whatever hair I have left. One final ‘bug’ I discovered, since we have been on the subject for quite a while, is that in ‘Variable’ and ‘Fixed’ modes, even though there are ‘Wide’ and ‘Narrow’ DSD filters present in the DAC operating system and advertised in the AK4191 datasheet, there really is no ‘Wide’ filter in these modes. Both cutoff at 19khz and have identical roll-offs. This may offer some insight into why Topping with the same chipset in their E70V Velvet didn’t bother to offer any DSD filter choices. The conspiracy theorist in me tends to believe all the bugs I experienced is why Topping didn't offer access to the 'Bypass mode' with their E70V Velvet DAC in the first place. As for you and my recommendations? If you pay attention to the ‘ND Color/Sound Color’ modes and how they interact with the ‘Bypass’ mode filters, you should have a lovely experience with this DAC. Sounds like a true ringing endorsement. But truly, if you can live with the issues, DSD playback using the ‘Bypass’ mode is just outstanding and is as good as anything at the price and more. In summary there is no doubt the S.M.S.L D400 PRO measurements are state-of-the-art. Having a true native DSD Bypass mode is a major, major plus. If you have a large collection of DSD files as I do, there will be nothing at this price that sounds better. Final opinion? It reminds me of Italian supercars. When they work, which is rare, they are like nothing else. With ownership of the D400 PRO, you may find yourself in a similar stressful conundrum, or merely experience minor annoyances, all depending on your perspective. OUR RATING: (0-10 scale. 8 or higher numbers represent best of industry. For the final score calculation, each category is given a (undisclosed) weighting and is tallied for final score. Although perfect 'fairness' is unlikely, our system tries to be as unbiased as possible. sound quality: 9.3 build quality: 9.6 ease of use: 9.2 measurements: 10.0 value: 8 TOTAL RATING: 92.0 In the Euphonic Review rating system, how are things like 'bugs', annoyances, and intangibles accounted for? The place where that makes a difference in the rating is at the VALUE line. Considering the price of the D400 PRO, combined with the headaches, well, frequently expounded on in the review, lowers its value score. We end up with the cheaper S.M.S.L D300 DAC actually coming out ahead of the D400 PRO. Yes the D300 had its issues, to the point I couldn't recommend it unless one was using ASIO drivers. But on some reflection, I don't consider that as big an issue as the D400 PRO DSD problems. The D400 PRO issues will affect everyone; the D300 issues will not. Plus the value proposition gives the D300 a real significant boost, given it comes in considerably less expensive than the D400 PRO. MEASUREMENTS For now, I have included as many of the measurements I feel confident in displaying. Thanks to E1DA for all the work they do. We could not even begin to make measurements of this quality just a couple years ago, short of buying $20,000 Audio Precision gear. Not for us. Well, not Yet.... The test results were truly astonishing. Both in how crazy good they are, and that E1DA now has a suite of measurement devices that can actually resolve at this level. Dynamic Range = 128.9db THD = -132.2db or 0.000025% THD+N = -123.6db or 0.000066% IM Distortion 19khz+20khz = -134.1 db (this is nuts) Jitter = 75ps peak / 5ps RMS (this was slightly disappointing. see graph below) Linearity = essentially perfect to -115db, finally 1db of error at -120db
0 Comments
Leave a Reply. |