PS Audio DirectStream (DS) DAC

by Karl Sigman on May 16, 2014 · 20 comments

in Digital

PS Audio recently released (March 2014) a new DAC to replace their already top-notch, high-end PerfectWave DAC (PWD), which I reviewed about a year ago, with a follow up review using it with the PerfectWave Bridge which enables using an ethernet cable to stream the digital files from computer to DAC instead of USB. The PWD, using ethernet, has become my reference DAC ever since. So, when I heard about this new one, I licked my chops at a chance to try it out on my system and review it.

PS Audio was kind enough to make this possible. This is its first review. The new one is called the DirectStream DAC (DS), the name referring to ‘direct stream digital’ (DSD), the digital encoding format for Super Audio CD (SACD) discs that lost out long ago commercially to the PCM (pulse-code modulation) format that is used in today’s ‘Red Book’ CDs (16/44.1 resolution), and in all higher-resolution files like 24/96 or 24/192.1. 1 PS Audio linked up with an eccentric and extraordinary engineer, Ted Smith, who is the lead designer and original prototype builder to create this ‘revolutionary’ DAC.

1. [The PCM notation x/y is short for x bits per sample of the amplitude of the analog signal at a sampling rate of y kHz. DSD uses a delta-sigma modulation method instead, in which samples of the delta (∆) (difference between successive samples) of the amplitude are measured and converted to a 1 bit per sample stream (of 0s or 1s) at a very high rate of 2.8224 MHz (denoted by DSD64), or at twice that rate, 5.6MHz (denoted by DSD128). The DS converts all fed to it into DSD128. 1]

The DS operates on an entirely different basis from the PWD or any DAC that I know of, and I point out right away that its main selling point is not to encourage people to go out and buy (waste money on?) expensive DSD high-resolution audio files: It’s to demonstrate that even CD 16/44.1 resolution PCM files can reveal extraordinary new details/harmonics when played properly, that is, in this new way. It is not about what format the audio is recorded in or converted to before it hits the DAC, it is about how you play it back: Whatever digital format you throw at the DS (PCM/DSD) gets converted by the DS to a 1-bit DSD digital stream, converted to analog and played bit perfect as such. This requires upsampling/processing the digital input into DSD format, and even DSD files too get upsampled to 30 bits at 10 times DSD rate then, for noise shaping, filtered/downsampled to twice the native DSD rate (yielding 5.6MHz) as the final 1 bit DSD product. The DS uses no off-the-shelf IC DAC chip such as the PWD’s superb Wolfson WM8741, or the very highly regarded ESS Sabre ES9018 used in many recent DACs that currently can handle/play DSD as input. In fact it uses no traditional such chip at all: Instead, it uses a field programmable gate array (FPGA); a Xilinx Spartan 6 FPGA.

This allows PS Audio to run proprietary software that does all the switching, digital conversion and filtering throughout. They are not unique by using FPGA in a DAC unit; but they are unique in the way they are using it, and for what purpose: to process (entirely) the digital signal to yield what is their ultimate goal—1 bit DSD format as output for anything originally handed to it and with no jitter. But, to accomplish this, they also (of course) have to deal with power supply and clock issues which involve other highly proprietary components/methods within the DS. The DS uses only one master clock, for example, PS Audio arguing that this reduces jitter even further. It is a very serious, very important and very expensive component of the DS: it is a voltage-controlled crystal oscillator (VCXO) made by Crystek Corporation. And, no, it is not an ‘atomic clock’—which quite frankly would be as silly as using Einstein’s General Theory of Relativity to ensure that one arrives on time to an 11:00AM meeting in room 311, when walking from one’s own office in room 310 next door at 10:59AM. Of particular note is that the path from digital input to analog output on the DS is much simpler and elegant than for the path required when using the very finest of PCM based processors; check out the diagram ‘Liberation from a Chip and Complexity’, under ‘Overview’ on the website.

One advantage of DSD as a format is that it is simple to just low pass filter it for conversion to analog. But, of course, this is easier said than done: PS Audio’s method of conversion at the end is very sophisticated involving the use of a passive (versus active) low pass filter via a passive audio output transformer. This results in another notable change from the PWD: the volume control is no longer a digital volume control built inside an IC DAC chip. This is actually a very important new feature. I have lately been using a passive preamp/attenuator for my PWD (instead of going directly from PWD to amps) since it sounds better (cleaner and more transparent) on my system than ‘direct to amps’: The volume level of the PWD is only bit perfect when at 100%, which is how it can (and should) be set when using an attenuator. DS volume control is bit perfect at any volume level. Thus, plugging directly into your amps and using the DAC’s volume control is now an even better justified option than it was for the PWD.

In any case, PS Audio claims that the increase of details and harmonics revealed/unmasked by the DS is a major improvement over traditional high-end DACs, and that this improvement is very significant even for CD rips, which are of course PCM at 16/44.1, and are the foundation for most people’s digital audio libraries. On the PS Audio website it states: ‘True DSD core engines (compared to the standard multibit Sigma-Delta converters followed by random lower quality multibit converters) offer advantages in simplicity, linearity, and in analog-like overload characteristics that avoid PCM’s hard clipping potential and a PCM processor’s propensity to mask subtle details.’

Intriguing indeed. I was intensely eager to carefully assess such claims—soundwise.

How does it look? How much does it cost?

The DS is hand made in Boulder Colorado USA and uses the identical chassis as the PWD (thus comes in either black or silver), complete with a top cover that is a beautiful hand-painted, hand-polished piano black. Its weight, 22 pounds, is identical to that of the PWD as well. I chose the silver model for the DS versus my black PWD so that visually I could tell them apart during various cable connection changes while testing; they look identical otherwise.

When it arrived, the DS came with a small card hand-signed by PS Audio CEO Paul McGowan stating that he had personally ‘Auditioned and Sound Quality Certified’ the DS, boldly displaying McGowan’s devotion for his products and to his customers. Owners of a PWD can buy a DirectStream Upgrade Kit at about $3000 that allows them to replace the inside of their PWD with new DS innards converting the PWD into a DS. A new DS on the other hand costs about $6000, which goes down to $4000 if you trade in your PWD towards it. The PWD itself is no longer being manufactured; it’s cost before the release of the DS had been $3995.00. The optional PerfectWave Bridge remains at about $800.00.

The back panel of the DS is also identical to that of the PWD; it has 7 different digital inputs (even including I2S via a HDMI cable) as well as ethernet if you install the PerfectWave Bridge, which is identical to that used for the PWD. In fact, the owner of a PWD with bridge can remove the bridge and install it into a new DS—no need to buy a new bridge; only a firmware update is required for its use. Both XLR and RCA analog output options are there as before too, and no external preamplifier is necessary—you can go direct to amps if you wish and use the DS internal volume control and balance control.

rear panel

rear panel

Changes in the touchscreen and filter options

Although the remote control looks identical to that for the PWD, the touch screen on the front of the DS is a little different looking, displaying different options and information than the PWD because of the dramatic internal changes in the way the DS works. For example, ‘Native X’ or other related filter modes no longer exist because they are now irrelevant: All files sent to the DS automatically get interpreted exactly as what they are and get automatically converted to a bit-perfect DSD end product as is. Bravo. The panel displays the type of file sent to it: PCM or DSD. For the PCM it shows the bit/rate details (16/44.1, 24/96, etc.). For DSD it displays whether the file is DSD64 or DS128.

The general approach of this review

The main purpose of this review is to report on the sound quality of the DS; in particular at first as compared against my reference PWD, using my reference Mojo Audio upgraded Mac Mini as music server using JRiver Media Center. Since I already use ethernet instead of USB for my PWD because it yields superior sound quality than USB on my system with the PWD, I performed extensive testing as follows:

1. USB on the DS versus ethernet on the PWD
2. Ethernet on the DS versus ethernet on the PWD; this requires having the PS Audio PefectWave Bridge installed on both units.
3. Ethernet on the DS versus USB on the DS
4. Connecting the DS directly to the amps versus using my attenuator—for volume control comparison.

The ‘A/B’ testing for (1) and (2) were made easier by using my attennuator which has two pairs of XLR inputs for handling two separate sources. PS Audio kindly lent me a second bridge so that both units had the bridge so as to make (2) simple to implement.

When the DS arrived, I installed the bridge right away so that a transition to the testing method of (2) would be easy—but of course I could not resist: I eagerly set up the ethernet connection and did so as follows: I manually assigned the DS the same IP address as the PWD, and just pulled out the crossover ethernet cable from the PWD and snapped it into the DS. JRiver Media Center 19 on my Mac Mini quickly showed the DS as a new device option, but very funny it was—it had a name: ‘Teds DAC’. Well done Mr. Smith. (The PWD shows up as ‘PerfectWave DAC’.) At this point I clicked on some music and out it came right away, so I kept clicking around to make sure all was working well; it was. The first thing I noticed was that the volume was lower than for the PWD. I needed about 3 steps more volume (on my attenuator) to equal that of the PWD. This was confirmed as normal by PS Audio; the volume control of the PWD was set higher (more gain) by design.

Although the sound of the new DS was somewhat edgy and thin indicating (as is normal) that it needed some burn in, it was already apparent from the start that something special was there: new details exposed (at the high and midrange frequencies in particular) and with exceptional imaging. My brother Nick, himself an audiophile, came by for some hours of listening after only 24 hours of continuous burn, and it took only about 30 minutes of A/B testing to conclude that we should just leave the DS connected and enjoy. So we did. He also helped me rearrange my entire system set up—taking advantage of the absence of my wife and young kids over the next 2/3 hours—so as to make it easier to see and change cables and such. We discarded my clumsy two-shelf piece behind the main system cabinet; it had been used for holding power strips, an internet hub and such. I offered it later that day (as a joke) to my wife as a great new modern piece of furniture; a potential gift from me and our daughters for upcoming Mother’s Day—she was not amused. Not even a chuckle; my credit card was to suffer an executive wallop later to make up for this faux pas.

Meanwhile, we put on a variety of CD rips —what a treat to hear them in this new way. I thus left the DS continuously playing 24 hours a day for the next 7 days by which time the sound became downright stunning.

Testing mode (2) done: DS is superior in sound quality to the PWD over ethernet. No contest. Ditto for (1); DS is superior yet again. The most surprising result to me was (3): I could not tell the difference in sound quality on the DS between USB (using a good cable) and ethernet. Now for the details.

Sound Quality

From the DS, cymbals, bells, blocks and other percussion had a rich and noble, long, natural lingering decay, and voices revealed a kind of resonating halo surrounding the singer offering extraordinary natural acoustics such as reverb. In general, individual instruments of any kind seemed to have more space and air surrounding them with the natural acoustics of their venue on display. Subtle details including external noises in live performances, such as clapping, breathing and tapping, were apparent more often and in a much stronger way. The imaging and transparency alone were mind-boggling. All of this was very noticeable. A sizzler cymbal, for example, sizzled away with a beautiful lingering decay.

Here is a cool example: While visiting my Audiophila colleague Martin Appel earlier in the week before I had the DS, he treated me to a listen on his truly outstanding vinyl set up of an album from 1972: War, ‘The World is a Ghetto’. The sound quality from his system was out of this world, so natural and earthy sounding; clearly an exceptional recording; the track ‘Four Cornered Room’ stuck out in particular. And, of course, it brought back great memories of the 1970s decade (and late 1960s) which is my heyday of learning, listening and playing (as a drummer) rock music. I sensed a dash of Pink Floyd, Jimi Hendrix and other giants of that time era in this music. I became very excited when I searched around and found out that a 40th Anniversary Edition CD had recently been released of the War album, so I purchased it immediately. I was let down. It did not sound so earthy and alive on my system as did Marty’s vinyl rig. It sounded somewhat compressed and dull. So, I obtained a 24/96 version hoping that might solve the problem. It did not; no better. On the DS, however, the sound of the CD rip came back to life. A cymbal bell’s ‘ding’ became a lingering ‘DING’, for example, and a wonderful psychedelic echo from the voices was there, ‘zoom, zoom zoom!’. The 24/96 version was also outstanding now. Interesting: When Appel and other audiophile friends came by to listen, they thought the CD version had a slightly warmer sound than the 24/96.

Having mentioned Jimi Hendrix, a really fascinating CD I recently acquired is by the guitarist Prasanna, ‘Electric Ganesha Land (tribute to Jimi Hendrix)’ - Susila Music, 2006. It sounds extraordinary on the DS. Track 4 ‘Dark Sundae in Tripiclane’ has startling imaging from the DS, for example. Prasanna plays electric guitar and electric fretted bass on the tracks but it contains a wonderful mix of influences involving jazz-rock fusion, and traditional Indian music including the playing of ancient Indian percussion instruments such as the Kanjira and Mridangam drums and the Morsing and Ghatam. The last track ‘Bowling for Peace’ is electric guitar with Kanjira, Mridangam and Ghatam and indeed is peaceful, but also exotic. I am lucky to have heard him play live several times with a variety of musicians in New York City. Most recently, at the Irridium, he played with a remarkable Tabla player (Nitin Mitta) as well as an amazing drummer Mauricio Zottarelli, who after the show kindly allowed me to get on stage and inspect his drum kit while peppering him with questions.

When I had my PWD, and not yet the DS, Prasanna had come by my apartment for some listening of music in general, and was very pleased and impressed at the sound quality. He has perfect pitch and strolled around my apartment to carefully listen to my system from different angles while commenting on the acoustics and offering critical advice. He went so far as to complain that it is a pity that most musicians today do not listen to their own music through a high-end system; they are as wound up in MP3, headphones and convenience as most others. The problem was that I had none of his music on hand; I had assumed he would bring me some—but he did not. Instead he brought me as a gift a Steely Dan CD ‘Two Against Nature’, because it was digitally recorded by Steely Dan instead of analog, and he wanted to hear it on a fine DAC. (In return, I gave him to take home the CD ‘Nu Made(Remixes)’ by The Balkan Beatbox because he found it fascinating when I had played it for him). I’ll have to have him come over again and hear his ‘Electric Ganesha Land’ CD on the DS.

As another example, the CD ‘Beethoven: Complete Works for Piano and Cello’ (Simone Dinnerstein on piano, Zuill Bailey on cello) which I have listened to so many times, and on different systems and DACs, took on a whole new life; I could now easily hear the cellist breathing on almost every track, as opposed to occasionally so—and only with careful listening effort—before. The richness and clarity of both instruments was so damn lifelike; mind-boggling yet again.

Drums/percussion on the following CD rips, which I have listened to so many times before now became truly exceptional in sound quality from the DS: Bill Bruford’s live Earthworks album ‘Random Acts of Happiness’, tracks 8 (‘With Friends Like These…’) and 9 (‘Speaking With Wooden Tongues’), in particular, and Patricia Barber’s ‘Cafe Blue’ album, tracks 4 (‘Mourning Grace’), and 5 (‘Nardis’). The sound from the DS truly made me believe that the percussionists were in my apartment. As another beautiful example, I recommend listening to the cymbal work on ‘Jazz in the Key of Blue’ by the Jimmy Cobb Quartet—through the DS. I even sat at my kitchen table, way to the side of my system, and yet, the gorgeous and delicate cymbal work came through with just amazing realism.

More on Cymbals

I had read online that some listeners of the DS had commented that ‘Just a Little Lovin’ from Shelby Lynne’s album of the same name now displayed remarkable life-like cymbal sounds; that the cymbal that is hit right at the beginning (once, and then occasionally later on) must be a ‘Zildjian’ cymbal, the famous company that originated in the 1600s near Constantinople (Instanbul) in the Ottoman (Turkish) Empire. The history itself of Zildjian cymbals is fascinating: The word ‘Zildjian’ means ‘son of cymbal maker’ in Armenian and was bestowed upon the Armenian alchemist named Avedis as his new name by the Sultan in the early 1600s who was enraptured by the extraordinary sound of Avedis’ cymbals created by using various mixtures of metals. The same family (many generations later) still owns and runs the business which is now located in Massachusetts, USA since 1929.

I decided I would take a listen myself to take a stab at assessing such claims of a Zildjian cymbal being used in ‘Just a Little Lovin’. I own three Zildjian cymbals, all made in the early 1970s when Avedis III was still the owner of the company; he is the one who opened the business in Massachusetts in 1929—he even became friends with Gene Krupa who helped him develop new models of cymbals such as the ‘swish’, and he got the company through the great depression. In the 1970s I played drums a great deal. But I had not used the cymbals for many years; I sold my drums long ago. These cymbals are probably worth a lot of money (they are in superb condition), but I have never had the heart to rid myself of them; for old times’ sake in the closet they have stayed. I could not resist: I took them out of the closet and hit them in various ways, with hands, sticks with plastic tips, sticks without plastic tips—startling my wife and kids. My young daughters were fascinated, which made the ‘testing’ even more fun. Meanwhile I acquired the ‘Just a Little Lovin’ CD and ripped it. The cymbal certainly did sound remarkable on the DS, with a powerful long decay and extraordinary clarity; and the lingering echo of the block was exceptional. (It’s a great recording in any case, stunning sounding from the DS.) I conjectured that the drummer was probably using a Zildjian ‘medium ride’ cymbal, and that his high-hats too were Zildjian. But then I Googled around a bit about the drummer, Gregg Field: What came up was the current Zildjian website with a whole page on Gregg Field mentioning that he is a ‘Representitive for Zildjian cymbals’. All his cymbals are Zildjian. Everyone knows that—except me apparently. I thus contemplated just selling my cymbals after all and buying my wife some jewels from the Sultan’s crown for next year’s Mother’s Day.

Using USB versus Ethernet

Unlike using ethernet cables, the use of USB cables—similar to the use of analog interconnect cables—can be very sensitive to choice of cable and length of cable if you have a high-end very transparent audio system. High-end USB cables, however, are expensive: roughly 100 times the expense of a 1 meter $4 − $6 ethernet cable. I had 3 of my favorite USB cables to play around with to compare with my ethernet set up. Conclusion for the DS: USB sounds as good as ethernet on the DS. In fact I think that now I have USB sounding better (slightly warmer, more natural). But, please decide for yourself—both inputs from my experiments yielded outstanding results.

One practical advantage of ethernet is that you can use very long cables and the sound quality does not deteriorate. As an experiment, I acquired a 50 foot long crossover ethernet cable (only $11.00) to replace my standard 6 foot one and I could not hear any sonic differences between the two—try doing that with USB! To use ethernet on the DS, however, just as for the PWD, requires the PerfectWave Bridge installed 2.

2. [A current problem is that the PerfectWave Bridge generally does not allow gapless play. But PS Audio is coming out with a ‘Bridge II’ that will allow that and much more. If gapless is really important to you, then by all means use USB.]

Playing DSD files

There are two methods of sending a DSD file to the DS, with the main one—widely available and used by essentially any DSD DAC—called DoP (‘DSD over PCM’). Various music server software support DoP by turning that function on in settings. For a Mac version of JRiver Media Center 19, for example, this merely requires turning on the ‘bit streaming’ setting to ‘DSD’. The DS can then play DSD files using USB, S/PDIF, among others, or even ethernet. But the DS also has in a limited way, the ability to receive DSD files directly as is. The way the DS can do this is via I2S (Integrated Interchip Sound) using an HDMI cable. But, this is not standard HDMI cable use, so you can’t just do this from your computer to the DAC using a HDMI cable. You need to have a I2S compatible device such as PS Audio’s NewWave Phono Converter (it converts vinyl analog to digital) to use this method. As a fascinating example: You can play vinyl on your turntable, have its analog sent out to the NewWave Phono Converter which then can convert it to DSD on the fly and send it digitally out I2S using an HDMI cable to the DS to play it.

DoP is widely accepted as sonically equivalent, and in fact on the DS there is no difference at all (explained later) so we will not dwell on this here. Suffice to say that I decided for fun and good measure to try out a handful of DSD files to compare sound quality on the DS when stacked next to high resolution PCM files. A DSD download currently typically costs about $25.00 for an album, which is expensive but similar in price to 24/192 PCM files that are widely available in comparison. Their size is large, about the same as a 24/192 PCM file; 2GB for an album is not unusual. I chose two DSD albums to acquire: ‘Come Away With Me’ by Norah Jones which I already had as PCM at 24/192 and ‘Kind of Blue’ by Miles Davis which I already had as PCM at 24/96 (both FLAC and really outstanding they are). Note, trying to compare the sound quality between PCM and DSD also involves how the recording on the file you have was mixed/remastered. If one sounds better to you than another, it might be for reasons that have nothing to do with DSD versus PCM. For example, both my 24/192 ‘Come Away With Me’ and DSD versions were made from the original analog master tape but with the 24/192 labeling by Blue Note Records in 2012 and remastered at Sterling Sound by engineer Greg Calbi and he DSD one labeled by Analouge Productions and remastered at Cohearent Audio by engineer Kevin Gray. The 24/96 ‘Kind of Blue’ was made from the original analog master tape by Sony Music Entertainment in 2013 and was remastered by their own Mark Wilder while the DSD one was taken from the original SACD DSD cuts. Apples and oranges?

First of all, the DSD played flawlessly right away on the DS; no different than when trying to play a PCM file. The touchscreen showed them as DSD64. I played Miles Davis first. Although the DS presented both with extraordinary details and such, the DSD was lower in volume than the PCM version and sounded a dash thinner and harsher. I liked the PCM best, a true masterpiece. Most likely it was because of the remastering/mix. As for the Norah Jones: Both sounded truly amazing from the DS, much closer to each other than for the Miles Davis, but once again I preferred the PCM, it had more air, resonance and the cymbals were more apparent and lingering. Her soothing voice had a wonderful natural resonance from the DS that I have never heard before on my system. And in the track ‘Shoot the Moon’, for example, the cymbal that occasionally gets hit (coming from the left channel), has that same kind of astonishing life-like lingering sound as I had confirmed in the Shelby Lynne CD rip ‘Just a Little Lovin’. (Is it a Zildjian? No comment.)

Direct to Amps

The use of my attenuator between the DAC and amps for volume control sounded outstanding. I had acquired it for the PWD mainly so that I could compare two sources side by side on my system, but found that I liked the resulting sound better as well. But I wanted to eliminate it for comparison with the DS. This is not an easy test to do: The attenuator requires two sets of analog interconnects, while the ‘direct to amps’ requires only one. The desired mix of two sets of interconnects that I had spent plenty of time choosing for sound was not possible to use: I had to choose only one set of the two. I chose at first the pair used for going from attenuator to amps; that made the most sense to me. The sound agreed, too: All the benefits that I had gained using the attenuator (exceptionally transparency, cleanliness and clarity) were still there. Great. I switched to different cables to try out for comparison; same basic result. Well done. I am not sure what method I will ultimately use, each one has advantages, with the most glaring one for the ‘direct to amps’ being the ability to use the remote control of the DS for volume instead of turning a knob on the attenuator. On the other hand, the attenuator makes it possible to compare two sources side by side, and allows having fun fiddling around with interconnects.

Paul McGowan (left) and Ted Smith of PS Audio. photo: PS Audio.

Paul McGowan (left) and Ted Smith of PS Audio. photo: PS Audio.

From The Horse’s Mouth

Paul McGowan was kind enough to get me in direct contact with lead designer of the DS, Ted Smith, who in turn was kind enough to directly answer questions via email that I had for him about the DS. I include here some of his answers and some of our back and forth.

I asked Smith how unique was the DS method of using a FPGA to do everything in a DAC (versus a traditional IC DAC chip) and its use of a single clock versus many clocks.

Smith: ‘I do not believe there are other DACs that use the FPGA for everything from “parsing” the input bits to outputting single bit DSD. There are a few other DACs that use sample rate conversion of all inputs to a single output frequency, but they use asynchronous sample rate conversion to convert from the incoming clock to the local clock or use a phase-lock loop (PLL) to drive the local clock. We use no input PLLs or FLLs (frequency-locked loops) and we use one master clock (and derive all other needed clock rates synchronously from that). As far as I know we are the only ones that do that.’

Because I was perplexed by my observations that the DS (unlike the PWD) was insensitive to USB versus ethernet (for sound quality), I asked him about such things.

Smith: ‘I’ve tried to make the DirectStream as input agnostic as I can: the FPGA knows no difference between the HDMI socket I2S inputs, USB or the Bridge (all are I2S to the FPGA). Any differences that are left are things like ground loops and radiation from high speed signals that might interfere with the rest of an audio system.’

I asked Smith about the differences (if any) of using DoP versus the possibility of sending DSD files directly in DSD format to the DS using I2S with an HDMI cable.

Smith:‘We can’t tell any difference in the DirectStream, in fact the I2S input routine encodes DSD as DoP so it doesn’t need to be treated specially downstream :).’

Finally, I asked Smith the following question: ‘Ted, because I was a drummer long ago, I use percussion (cymbals, drums, etc.) to listen carefully (for testing purposes) because I know personally how they really sound live. My father played piano throughout my childhood so that instrument too I tend to use. What instruments (if any) do you find helpful in assessing sound quality, and did you use any in “fine-tuning” the DS?’

Smith: ‘Howdy Karl: I agree that of the sounds we can hear (and process) the best are the ones we have large amounts of experience with. I’ve played clarinet, trombone in bands, played piano, sung in choirs, and hence the instruments in a band, piano and voice are very useful for me personally. But in truth, after a while I just see whether a potential hardware or software change makes me want to tap my feet. When I have friends over I pay less attention to what they say than to their expressions while listening. In the last few months before production Paul and some of his associates listened to the DAC carefully and made suggestions to me as to what they thought it might be missing or how it could be improved. I translated that into potential technical changes and if those changes lead to a more technically correct DAC and kept my feet tapping I was happy to implement them: e.g. removing capacitors that were just there for EMI protection that weren’t actually needed for that or laying things out in the FPGA a little more carefully to avoid crosstalk with the output signals, etc.’


The DS is a game changer; I think it has caused the ‘war’ between DSD and PCM to be on hold or mute for most of us, and above all hold your horses before buying expensive high-resolution PCM files or DSD. That alone is a major accomplishment. McGowan, on one of his recent daily posts, stated in words the following as PS Audio’s core values/principles: ‘At our core we give the middle finger to the impossible. When someone tells me it’s impossible to make a $6K DAC sound better than a $30K DAC, or a $700 integrated as good as a multi-thousand dollar one, that’s the reaction I get; although I refrain from that gesture. The impossible becomes possible when someone achieves it.’

PS Audio has perhaps achieved the impossible with the DS. Besides, one can now listen to a CD rip of War’s ‘Four Cornered Room’ without having to be high wearing bell-bottoms in order to appreciate it. The DS gets my highest recommendation; hats off and a bow to PS Audio.

[It is with great pleasure that we award the Audiophilia Star Component Award to the PS Audio DirectStream (DS) DAC. Congratulations! - Ed]

PS Audio DirectStream DAC

Manufactured by PS Audio
4826 Sterling Drive, Boulder, Colorado 80301
Phone: (720) 406-8946
Fax: (720) 406-8967


Price: $5999.95
Source: Manufacturer loan


Unit Weight 22 lbs [13.5 kg]
Unit Dimensions 14 x 17 x 4 [ 36cm x 43cm x 10cm]
Shipping Weight 31 lbs [19 kg]
Shipping Dimensions 20.5x 24 x 10 [52cm x 61cm x 25cm]

Power requirements:
Input Power Model specific 100VAC, 120VAC, or 230VAC 50 or 60Hz
Power Consumption 30W

Digital audio inputs:
I2S(2), Coax, XLR Balanced, TOSLINK, USB, Network Bridge slot

Sample Rates:
I2S,S/PDIF, and USB — 44.1kHz to 192kHz 16bit, 24bit, DSD 64, DSD 128
TOSLINK 44.1kHz to 96kHz 16bit, 24bit

Analog Audio Output:
Connector RCA/XLR Unbalanced /Balanced (X2)
Output level, low 1.41 Vrms(+5BV)/3.15
Output level high, maximum 2.81 Vrms (+8dBV)/5.3 Vrms (+12dBV)
Output Impedance 100/200
Frequency Response 20-20KHz +/- 0.25dB
THD+N @ 1KHz (full scale) <0.03%
Output Stage Passive audio transformer, fed by high current, high speed analog amps producing d

Data Handling:
Format PCM or DSD
Sample rate (PCM) 44.1kHz, 48.0kHz, 88.2kHz, 96.0kHz, 176.4kHz, 192kHz
Word length (PCM) 16b, 18b, 20b, 24b
Data rate (DSD) Standard (2.8MHz) or Double (5.6MHz) DoP on all inputs as well as raw DSD on I2
Input jitter reduction effectively 100%, residual immeasurable. No input PLLs, FLLs.
Input Processing 170MHz
Signal Processing 50MHz
Synchronous Upsampling, all inputs 28.224MHz
Digital Processing S/N ration >146 dB
Digital Volume Control Zero loss of precision
Analog Conversion method Delta Sigma (DSD) Single-bit double rate

I2S Digital Input:
Connector HDMI
Format PCM or DSD. DoP on all inputs as well as raw DSD on I2S inputs

USB Digital Input:
Connector USB B Type
Format PCM or DoP v1.1 (DSD over PCM)
Transfer mode Asynchronous

Associated Equipment

Music Server: Mojo Audio upgraded Mac-Mini with Joule III Power supply and powerless
firewire cable
Speakers: Alta Audio FRM-2
DAC: PS Audio PerfectWave MKII DAC with Bridge using a crossover ethernet cable from
Mac-Mini to DAC (no USB used)
USB cables (from Mac-Mini to DS): Wireworld Platinum Starlight, Silnote Audio Poseidon,
Audioquest Diamond
Amplifiers: 2 Hephaestus Audio Harpocrates Monoblocks (Special Edition)
Passive preamplifier (between DAC and amps): Goldpoint SA2X-I Balanced Stereo
Mini-V Precision Stepped Level Control
Power Conditioner: PS Audio P3 Power Plant
Speaker cables (with jumpers) and all power cords: Waveform Fidelity GSIII
(formerly known as Kaplan Cable)
XLR Interconnect cables: Waveform Fidelity GSIII, Morrow Audio MA7 Grand Reference,
Mojo Audio Lucent SE (Signature Edition)

{ 2 trackbacks }

PS Audio DirectStream DAC - Page 15
05.17.14 at 3:33 am
Review: PS Audio Directstream DSD DAC | Confessions of a Part-Time Audiophile
04.11.15 at 7:00 am

{ 18 comments… read them below or add one }

admin 05.16.14 at 12:17 pm

Congratulations, Karl, on the first review of this obviously exceptional DAC. Your review was incredibly detailed and captured the sound essence of the DAC. I’m looking forward to hearing against the Bel Canto 3.5 Mk II.

Great job.

Cheers, a

Karl Sigman 05.16.14 at 12:51 pm

Thanks Anthony, you are most welcome.

marvin fox 05.17.14 at 6:25 pm

You used a cheap mac mini with this fine piece of equipment incredible indeed.

Karl Sigman 05.17.14 at 8:11 pm

Sorry to hear that you think money=good sound.
One of PS Audio’s most admirable qualities is its emphasis on extraordinary high-end quality at relatively low prices.
Even its CEO Paul McGowan now uses a “cheap” Mac Mini at times to show case this very same DS DAC.
Anyhow, you might want to read up on how to make
a Mac Mini into an outstanding music server here:

admin 05.17.14 at 8:19 pm

Mr. Fox. Would you please elaborate. Thx.

Mike Norton 05.18.14 at 3:20 am

Hi Karl
Great and accurate review.
Received our Psd Friday ,customers that have heard it so far are blown away.
In my opinion it opens the door on a whole new world of digital audio.A totally ground breaking product that gives life to the musical time machine

Brodie 05.18.14 at 3:21 am

Curious whether the DS was powered by the Power Plant P3 for the review? And whether there has been any assessment of DS sonics when powered from P3 compared with un-regulated power. Does the DS have a volume limiter setting configurable in the software?

AGB 05.18.14 at 9:27 am

RE: marvin fox 05.17.14 at 6:25 pm
“You used a cheap mac mini with this fine piece of equipment incredible indeed.”

The reviewer could have used a toilet plunger or a soda straw. The FPGA with properly implemented USB input is relatively insensitive to the source device. Fancy power supplies for the mini will make little difference if any. Sure, nice to have. Bespoke shoes are nice to have too, but you’ll probably walk just as well in John Kerry-branded flip flops.

From my relatively little experience, let me state this belief:

FPGA-based DACS have the potential to outperform by miles custom made DAC chips simply because even custom DAC chips made from individual resistors have only so many ladders and figurative “step” with which the designer can work. All a custom made DAC array can provide over off the shelf is superior precision.

The Spartan-6 FPGA has tens of thousands. Not dozens. The Spartan is programmable. The custom DAC needs external chips of minimal programing capacity. The Spartan has many cores around which a good engineer can surround it with other cores, memory, regulation. A custom made DAC has no core, and external supporting techniques cannot make of the sow’s ear a silk purse - no matter what the designer wants out of his design. I’ll appreciate any corrections to my understanding as stated here.

Correctly implemented an FPGA DAC has unlimited potential, and in a few years we’ll have FPGAs of orders of magnitude more taps…that’ll be interesting. The FPGA DAC (subject to correct implementation) is itself an order of magnitude improvement over off the shelf chip-based DACs because their noise shaping - the essence of digital design and necessary for conversion - is far, far, better than off the shelf chip-based DACs. The FPGA DAC eliminates jitter better at the very beginning and in addition to other reasons, because its noise performance is far better. Noise causes jitter. Eliminate jitter with buffers and clocking is one thing. Eliminate it with lower noise is another.

Lastly I think, considering the processing advantages inherent in the FPGA architecture, and that PS is but one company among very few capable of designing FPGA DACs, the competition is in serious trouble. What I mean by that statement is that the competition using very expensive platinum or gold cased custom DACs, Rings or what have you, still cannot achieve the best FPGA-based designs, even though their cost is multiples of the FPGA-design.

What I hear with FPGA design is information density and the correct arrangement of the music’s fundamental texture and tone.

It now appears that all of us (especially us analogphiles) were wrong - I MEAN DEAD WRONG - about the limitations of the CD medium (ripped CDs to be specific.) CD’s are capable of holding substantially most of the information recorded (admittedly in some cases hi rez is better provided it is played back in its native format.) It is just that it took FPGA technology to realize in reality what the theoreticians insisted in theory about the 44.1/16.

Your CD libraries listened through capable FPGA-based DACs will blow your minds.

rexp 05.19.14 at 12:43 am

Very well written review! Covered all the bases, i guess mr fox just wanted to know what it sounds like with a dedicated transport. Personally i think even vlc media player sounds better than jriver, would be interested to hear your thoughts.

Rorie 05.19.14 at 7:40 am

Thank you for pointing out that ultimately mastering is the most important part of the process not the format type! Another online zine trumpets DSD as the be all and end all…NOT!

However i would contend your review on one point:

DSD albums are $25? …..sure if they are samplers you can get them for even less $20…but the overwhelming majority that i have looked at today form several sites are from $36 to $50…that is at least ON AVERAGE 60% more then you suggest

Karl Sigman 05.19.14 at 7:45 am

Dear Rorie,

Wow! Thanks. Now that is expensive. But the two I mentioned in the review indeed were $25. I also have Steely Dan `Gaucho’ at $25 too. Your prices suggest further that we should be careful in buying such things in general.

Cookie Marenco 05.19.14 at 10:29 am

Excellent article! I appreciate that you went into some detail about the difference that a mastering session can make on the outcome of a recording. It’s a very difficult subject for most people to understand. I’m curious if you had a chance to compare the same recording (maybe Norah Jones) at the same sample rate from different mastering sessions.

I heard the Blue Note remastering of Kind of Blue maybe 10 years ago in DSD (at Gus Skinas’ place). This had been one of my favorite recordings as a jazz player that I had listened to on vinyl regularly. I was pretty horrified at the remastering of the SACD. Did they remaster again? I haven’t kept track.

That happened to a lot of great analog recordings when remastered for CD or SACD. It wasn’t the fault of the medium. It was the re-mastering engineer thinking they were ‘improving’ the sound. Ouch! Remastering will make more difference than format many times over. I’m thankful you’ve pointed that out.

At Blue Coast we do all of our mastering for digital in house and are careful to add the provenance/heritage of the recording. Some engineers willfully create a different sound for the CD, SACD, downloads and vinyl recordings to optimize each format. If you need files that have not been altered for each format (except for conversion) please let us know. We can provide ‘trusted tracks’ from source recording to download for comparing gear.

By the way, drums are my favorite instrument to record. Like snowflakes, no drum set is ever the same when recording. :) Piano is my instrument (since I was 4 years old). It was the cymbals and the piano sound recorded in PCM that moved me to return to analog and DSD. The clickity clack of stick hitting cymbal drove me crazy in PCM.

Thank you again for your insightful and detailed descriptions!
Cookie Marenco
Blue Coast Records

Karl Sigman 05.19.14 at 10:31 am

RE: rexp 05.19.14 at 12:43 am
`Personally i think even vlc media player sounds better than jriver, would be interested to hear your thoughts.’

Since I have the Bridge installed enabling me to stream my files directly from computer to DAC using an ethernet cable (instead of USB), I can only use
player software that supports Portable Universal Plug and Play (UPnP). JRiver Media Center supports UPnP. Most other player softwares do not.
I certainly do plan now to explore other (non PPnP) options since I am back to enjoying USB.

alan 05.19.14 at 3:06 pm

RE: rexp 05.19.14 at 12:43 am
`Personally i think even vlc media player sounds better than jriver, would be interested to hear your thoughts.’

I tried JRiver extensively for sound quality and potential operating glitches; I really liked some of its features. The only reason I did not buy it then is that when I compared its sound quality to the free PSaudio eLyric’s, there was a clear nod to eLyric in the upper mid frequencies: the presentation was clearer and more lifelike. Since both media players supposedly presented the same bits to the DAC (PWD), my only conclusion was that they didn’t. possibly eLyric somehow equalizes its output in a way that is more favorable to my system and personal preference. Beyond that, I won’t speculate.

bmoura 05.19.14 at 4:12 pm

$25 may sound expensive for a Stereo DSD Download. But when you consider that used copies of Stereo SACDs like Thriller start at $365 (new) and $100 (used copies) on Amazon.Com, it’s quite a bargain for some albums!

Karl Sigman 05.21.14 at 10:14 am

re: Cookie Marenco 05.19.14 at 10:29 am

Dear Cookie, thank you very much for your kind words; it is a pleasure to hear from you. And since I will not be letting the DS out of my sight, I will need advice (from you/Blue Coast) over the next weeks for some excellent DSD examples.
Best wishes, and some great sounds of piano and cymbals,

Karl Sigman 06.28.14 at 11:24 pm

Dear Ross, in my case I am using a “crossover” ethernet cable (directly from Mac Mini to DAC, no hub in between) in which case IP addresses are thus not assigned by the network, you must assign one yourself. (In fact the network is totally off when I do this.)

Peter Wighton 07.02.14 at 10:08 pm

I take it from the picture of the rear of this gizmo (Pardon!!) that it is strictly a 2-channel offering?

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