Friday 30 May 2014

The PS Audio DirectStream DAC - Part III.

When seeking to convey what the DirectStream achieves with high resolution source material you can never afford to ignore the garbage-in garbage-out principal.  High resolution implies that we are talking about source material which rises above and beyond the performance delivered by lower-resolution source material, by which we must assume in turn we are referring to Red Book CD program material.  Extending this argument further, it means that we are obliged to confine ourselves to source material of impeccable pedigree.  It also follows that, unless we spend most of our time listening to DACs of the highest possible pedigree (which I have at times had the opportunity to do), when we hear exceptional playback of an exceptional recording we generally don’t have a context in which to place a qualitative assessment of what we hear.  So in my description of what follows, bear that in mind.

First up, “Quiet Winter Night”, a folk-jazz album by the Hoff Ensemble, from Morton Lindberg at 2L in Norway.  This is a 24-bit 352.8kHz (so-called DXD) recording, which is the format in which the original recording was made.  2L makes all of their recordings available in this format if that is what you want.  I know of nowhere else where you can purchase the entire catalog of a no-compromise audiophile label in what is truly the Original Studio Master format.  They also make available a huge selection of free downloads in a bewildering array of formats, including multi-channel, DSD, and original studio master DXD.  Since the DirectStream does not support 352.8kHz PCM, BitPerfect downsamples it to 176.4kHz.  The sound is effortless and spacious, having been made in the reverberant soundstage of a small church in Oslo.  The instruments are all acoustic, apart from a Strat, and are grouped tightly together.  The recording has a “live” feel, although there is no audience.  It has a slightly bass-heavy ambience, which to my ears is typical of 2L.  Perhaps bass-heavy is wrong.  Maybe I mean bass-weighty.  Because the microphones are very close to the instruments, and there is little in the way of studio adulteration going on, I think they naturally pick up more of the “weight” of the bass drum and double bass than you would normally hear from a typical listening position.  But in any case the DirectStream does a terrific job of presenting the individual instruments and voices, locating them precisely in space.  The percussion in particular is presented with a lightness of touch and clarity of texture, but with appropriate weight in the bass.

"RĂ©sonance" is a recording of solo Viola Da Gamba music by Nima Ben David, from Todd Garfinkel’s MA Recordings.  I believe the original master recording was made in DSD, and what I have is a 24-bit 176.4kHz conversion.  This recording is quite honestly like being in an intimate highly reverberant studio space with the performer.  Ms Ben David is right in front of you, so much so that getting the volume absolutely correct within 0.5dB is crucial to making it sound right.  The scrape of the bow across the strings is captured cleanly.  The tonality of the instrument is wonderfully present, and, try as I might to listen analytically to the sound, I find myself being drawn inexorably into the music.  The Viola Da Gamba is a predecessor of the ‘cello but with a sound which is at once less refined, with some of the weighty tone of a double-bass, but in the hands of Ms Ben David ethereally expressive.  And in the hands of the DirectStream, there is little to want for in the sound.  The DirectStream’s magical bass was made for music like this.

Meet Me In London” by Antonio Forcione & Sabina Sciubba, produced back in 1998 by Naim Records, is probably the one “Audiophile” record that truly stands up on its own two feet as a musical experience.  It is a collection of covers and standards that showcase Sciubba’s poised and controlled vocal, with Forcione’s dexterous acoustic guitar work, backed up by delicious bass, and occasional other musicians as required.  The recording was magnificently captured by Naim, and remastered specially for the 24-bit 192kHz digital download which I have.  The DirectStream reproduces this recording beautifully, with the texture and dynamics of Forcione’s guitar work a particular joy to listen to.  The bass is wonderfully tasty, with real presence and weight.  Sciubba’s vocal is easy on the ear and shows remarkable restraint in terms of dynamic compression, but some compression is inevitably there, and the DirectStream makes it plain if you want to go to the trouble of listening for it.  I feel I want to use the word “presence” here again.  This is emerging as one of the core characteristics of the DirectStream - it has consistently great “presence”.

I have an odd track - I have no idea where it came from, or who the performers are - but it is a beauty.  It is an excerpt from Copland’s “Fanfare For The Common Man”, and was recorded by someone who had a wonderful idea:  “Why don’t we do a proper job of capturing those drums?”.  Both bass drum and tympani are prominently featured on this recording, and the DirectStream gives free rein to both, limited only by the bass response of my speakers which doesn’t go down much below 28Hz (and neither does my room, for that matter).  But when the bass drum strikes, it has an enthrallingly accurate and detectable pitch, something that I have previously only heard before on seriously good headphones, such as Tim’s Stax SR009s.  The bloom and decay are wonderfully accurate.

Moving on to DSD.  In terms of its specifications, what the DirectStream offers that its predecessors did not, is DSD support.  I have left this aspect until last, because I don’t want to over-emphasize its importance.  While DSD is at the core of how the DirectStream functions, I would not wish to suggest that it should only be of interest to those with a DSD collection.  Far from it - it is a high-performance DAC that happens to do DSD.  But its DSD performance still needs to be examined.

Let me review what I think of DSD at this point in time, recognizing that this a moving, evolving target.  For me, the bottom line is that the best sounds I have ever heard have been produced by DSD.  At BitPerfect we are quite involved in format conversions between DSD and PCM.  We have found that the very best DSD-to-PCM conversions we know of - those produced by our DSD Master product - can be very, very close to their DSD originals.  The differences are really quite subtle.  We can also do it the other way round - make conversions from PCM originals to DSD - but the best quality PCM-to-DSD conversions are still those made by professional third party software such as Weiss Saracon.

An interesting thing happens when we make PCM conversions from two types of DSD recordings.  The first type are original DSD recordings that have never seen PCM, while the second type are DSD conversions from a PCM master.  What we have found in the past is that PCM conversions made from “pure” DSD masters (i.e. the first type) are not quite as good as the DSD originals, whereas those made from “impure” DSD masters (i.e. the second type) can be much harder to distinguish from the DSD master.  This suggests that a certain “PCM-ness” may be imprinted upon a recording whenever it enters a PCM format, and that once having acquired this “PCM-ness”, it can never again regain what you might call its “DSD-ness”.  All very wishy-washy, I know, and not at all scientific (although I do have a rational basis for making that argument).  And given that all this was determined exclusively using the Light Harmonic Da Vinci Dual DAC, it is far from conclusive either.  But I wanted to mention it, because one of the things I want to accomplish with the DirectStream is to see if the same sort of behaviour can be evinced using it.  And just to be clear, I am only going to report preliminary findings in this post.  We’ll be doing a lot more work with the DirectStream in this area down the road, and may report on that later if I come up with anything interesting.

In comparing PCM and DSD versions of the same track, how can you avoid comparing Apples and Oranges at some point?  Unless you have access to detailed information concerning how the different versions were mastered, how do you know that what you are hearing is not ultimately a difference in the mastering that you end up ascribing to a component in the review system?  To attempt to minimize these issues, I set about using DSD Master to make a number of PCM conversions from a selection of DSD tracks that I have, and comparing what I heard from them.  That way, the only differences inherent in the source material are those arising from DSD Master’s ministrations, which, if nothing else, are at least known.  In each case the PCM versions were 16-bit 44.1kHz, 24-bit 88.2kHz, and 24-bit 176.4kHz, and all were in Apple Lossless format.  The DSD tracks were a mixture of “first-type” and “second-type” DSD64 recordings; mostly the latter since the true provenance of a DSD recording is actually desperately hard to establish conclusively.

I don’t have the time to go into details but the results were all remarkably consistent.  First of all, the differences - from CD all the way up to DSD - were much smaller than I expected them to be, and the most noticeable of these differences was moving up from CD to 24/88.2, which is probably due to the step up in bit depth.  With each upward step in format resolution the same two general things were observed to happen.  The bass got cleaner and firmer, and the detail resolution of instruments across the spectrum improved.  The soundstage imaging got crisper, and everything just seemed to acquire that extra smidgeon of presence.  However, the difference between 24/176.4 PCM and DSD was most often too difficult to reliably detect.  I suppose I should be making a big deal of that - how DSD Master produces PCM conversions which are close to indistinguishable from DSD - and yes these conversions are good, but I don’t think that’s the whole story here.

The bottom line is that the DirectStream produces exceptionally good sounds playing DSD material, but it also produces virtually indistinguishable sounds playing DSD Master’s PCM conversions of the same material.  If pushed to get off the fence here, I would suggest that the DirectStream’s DSD processing may be at the root of this.  Using the terminology I introduced earlier, it sounds to my ears as though the DSD processing in the DirectStream may be introducing “PCM-ness” into the DSD data stream.  We should not lose sight of the fact that there is a lot of signal processing going on in the DirectStream, just as there is in other DACs built using common commercial DAC chipsets.  Each of those chipsets uses its own proprietary implementations of those signal processing algorithms, and DirectStream merely has its own.  This signal processing is wickedly complex, and does not yield to a few pithy sentences.  It is also an area in which great progress will continue to be made, aided by the inexorable advancements which will continue to be made in signal processing technology.

In summary, the DirectStream is very nearly the best DAC that has ever passed through my system, yielding only to the Light Harmonic Da Vinci Dual DAC.  At $6,000 it is far from cheap.  But if you are willing to consider spending that kind of moolah, the DirectStream handily outperforms anything I have heard for anything short of seriously silly money.  And since PS Audio has a pretty comprehensive worldwide dealer network, the prospects of being able to audition one locally are better than for a lot of its serious competition.

As a kind of coda to this review, I have implied that the Light Harmonic Da Vinci Dual DAC is better than the DirectStream, and indeed it is.  I lived with one for the best part of a year.  But it comes in at $31,000 last time I looked.  What do you get for the extra $25,000?  Simply put, the Da Vinci places the performers right there in the room with you.  Sonic textures are so convincingly real.  If you can describe the DirectStream's sense of presence as exceptional, then that of the Da Vinci is quite uncanny.  It can make you stop and turn your head when you are elsewhere in the house, which is something you have to experience to believe, and is a party trick the DirectStream cannot quite pull off.  It is possible, though, that the DirectStream’s bass might be even better than that of the Da Vinci.  Listening to DSD on the Da Vinci can be heartbreakingly good, just as the Linn Sondek LP12 was, in its way, when it burst on the scene nearly 40 years ago.  The Da Vinci Dual DAC illuminates differences between PCM and DSD which the DirectStream apparently cannot.  Granted, those differences probe deeply into the realm of diminishing returns.  So if a Da Vinci Dual DAC costs $31,000 how much is a DirectStream worth?  I would suggest that $6,000 sounds more and more like an absolute steal.

Read my follow-up review on the important 1.2.1 firmware update.