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PS Audio PerfectWave disc transport/DirectStream DAC (with Pikes Peak OS)

PS Audio PerfectWave disc transport/DirectStream DAC (with Pikes Peak OS)

Not so long ago the Boulder, Colorado-based firm PS Audio touted its PCM-focused PerfectWave DAC and matching PerfectWave Transport as its premier digital audio products, but all that changed with the arrival of the firm’s DSD-centric DirectStream DAC (£5,250, or £5,550, with PS Audio’s optional PerfectWave Bridge module installed).

In the years following the PerfectWave DAC’s release, PS Audio President Paul McGowan was approached by DAC designer Ted Smith. Smith (who has since become a key member of the PS Audio engineering team) suggested a superior-sounding DAC based on a DSD (Direct Stream Digital) rather than a PCM platform. Once McGowan, along with some trusted cohorts from the Pro Audio/Recording Studio world, had a chance to hear Smith’s proof-of-concept DAC circuits in action, the sonic results spoke for themselves, leading PS Audio to embark upon development of the DirectStream DAC. Another key member of the PS Audio team is legendary high-end audio designer Arnie Nudell (creator of, among other things, the classic Infinity IRS loudspeaker); Nudell’s expert ears are used to vet new PS Audio design concepts, subsequent product and firmware revisions, and so on.

, PS Audio PerfectWave disc transport/DirectStream DAC (with Pikes Peak OS)

The operating principles of the DirectStream DAC are fairly easy to grasp. All incoming PCM digital audio data is first converted to DSD format and then upsampled to 10x the standard DSD rate; similarly, all DSD digital audio files are likewise upsampled to the 10x DSD rate. Then, the 10x DSD digital audio data is converted back down to the double DSD rate for playback. Handling all of this up- and down-conversion is what PS Audio calls its ‘DSD Engine’, which uses an FPGA (Field Programmable Gate Array) as its core processor. No off-the-shelf DAC chips are used in the design.

To drive the outputs of the DAC, PS Audio employs high-speed, fully balanced video switching amplifiers whose outputs are routed through an extremely high quality, wide bandwidth audio transformer that serves, says PS Audio, to provide “both galvanic isolation from the outside world as well as low pass filtering.”

All of the above takes place within an extremely low-jitter (and relatively jitter insensitive) environment made possible by the firm’s decision to use one single master clock for the entire DAC—a clock that, according to PS Audio, is “designed to subtend all possible combinations of sub-clocks, from 44.1, 88.2, 48, 96 (kHz), etc. in order to eliminate the need for multiple clocks…” The clock deliberately does not use “classic edge detection techniques on the digital input data,” but rather uses “a proprietary method of extremely fast sample-and-recognise technology” that is said to minimise sonic degradation related to “cables, jitter, and the quality of the incoming data source.” Moreover, PS Audio has taken special care to avoid noise transfer between sections within the DAC, while paying extremely close attention to circuit board trace layouts to minimise both noise and potential jitter issues.


While this technical description sounds promising, one key question remains: why go with a DSD-centric DAC in the first place? The answer is a multi-faceted one, but let me attempt, here, to synopsise a mini-White Paper PS Audio has provided on the subject. The designers chose DSD as the core platform for this DAC with several thoughts in mind. First, DSD is simple to convert to analogue, requiring only a low-pass filter. Second, DSD is inherently linear and all bits in a DSD stream have the same weight, meaning, says PS Audio’s White Paper, “a single-bit error anywhere is barely measurable let alone audible” (something that is not always true with conventional PCM playback). Third, DSD soft clips when overdriven, meaning that a DSD-based DAC should theoretically behave more like analogue magnetic tape, where “signals which exceed the nominal full scale value only get slightly compressed if at all.”

, PS Audio PerfectWave disc transport/DirectStream DAC (with Pikes Peak OS)

The DirectStream DAC provides a card slot for an optional Network Bridge module, plus a range of digital inputs including AES/EBU (via XLR), coaxial and TOSlink S/PDIF, I2S, and USB. Two methods of control are provided: a full-colour touchscreen display and a convenient, handheld remote. Many different display views are possible, but the standard one shows the DAC input selected, the sampling rate and bit-depth of the file in play, and the absolute phase setting chosen (the DirectStream DAC allows switching of absolute phase, which makes a significant difference on some recordings).

If the optional Network Bridge is installed, the DirectStream DAC will automatically access the Internet to look up album art and metadata for the files being played and then store that data on an included SD memory card. Thereafter, the display will show the appropriate album art and metadata whenever the file is played. The display screen also will temporarily show volume and/or channel balance settings whenever users adjust either parameter. Although the DAC can be set to provide fixed, line-level outputs, PS Audio strongly recommends using the DAC’s variable level analogue outputs (either balanced or single-ended) to drive power amplifiers directly, arguing that there is nothing quite like the sonic transparency and purity that results. Consequently, I ran the DAC directly into my reference monoblock amps.

According to its specifications, the DirectStream DAC can handle PCM files at up to 192kHz/24-bit resolutions, but I got a pleasant surprise when I discovered the DAC could happily play the 352.8kHz/24-bit DXD files I had on hand (and it sounded terrific doing so!). The DAC also is rated to handle DSD64 and DSD128 files, which it does with the greatest of ease (but note: it cannot play ‘quad speed’ DSD256 files).

In the title of this article, I mentioned that our review sample of the DirectStream DAC had PS Audio’s latest Pikes Peak ‘OS’ or ‘operating system’ installed. I used that phrasing because PS Audio describes its elaborate control firmware for this DAC as being not unlike a full-fledged computer operating system, owing to the extreme volume and complexity of the code involved. To date, there have been three operating system updates for the DAC – all free of charge – and according to Paul McGowan (and others in the PS Audio user community), the Pikes Peak OS represents a bigger sonic step forward than any of the previous upgrades.


The DirectStream DAC is one of the most analogue-like digital audio products I’ve yet heard. By this I mean that its sound reminds me of a very high-quality analogue reel-to-reel tape deck, but of course without any tape hiss at all. In practical terms this means that when playing well-recorded material, the DAC can and does present plenty of inner detail and dynamic nuance, while also serving up remarkably three-dimensional soundstages, yet it does so without ever sounding as if it is working hard. On the contrary, the DAC consistently conveys a sense of relaxed and unstrained smoothness coupled with full-bodied dynamics that—exactly as PS Audio promised—refuse to veer into raw-edged overload. Perhaps a good word to describe the DirectStream DAC’s sound, then, would be ‘graciousness’, in the fullest and most deeply resonant senses of that word.

, PS Audio PerfectWave disc transport/DirectStream DAC (with Pikes Peak OS)

Put on truly well recorded material, such as the Nidaros Cathedral Girl’s Choir & TrondhiemSolistene performance of Kim André Arnesen’s ‘Magnificat’ [2L music Blu-ray/hybrid SACD] and listen to the way the PS Audio delineates, yet refrains from clinically dissecting, the elements of the music. The DAC effortlessly captures the high, pure, multi-layered and achingly beautiful voices of the girl’s choir. Similarly, it beautifully renders the tonality of the accompanying strings; reproduces the deep, powerful, yet very taut voice of the pipe organ; and above all captures the remarkable depth, width, and reverberant qualities of the Nidaros Cathedral itself. In short, the DirectStream DAC serves up glorious musical realism, in a disarmingly casual and almost self-effacing way.

Given the DirectStream DAC’s internal architecture, you might think it would give ‘preferential treatment’ to DSD material and indeed it does sound quite masterful when playing DSD files. But the real magic of this DAC may centre on its handling of PCM material—material the DAC gives greater smoothness, fluidity, dimensionality, and elegance than it might otherwise have had. I don’t mean to suggest by this that traditional PCM playback methods cannot or do not sound perfectly good in their own right, because they certainly can and do. But if PCM playback has an identifiable ‘failure mode’ it might be that PCM files can at times sound a bit flat and 2-dimensional, while exhibiting subtly edgy and/or mechanical qualities that tend to hold the listener at arm’s length from the music. While I would not tell you that the DirectStream DAC makes these problems disappear with a wave of its magic DSD-processing wand, I will tell you that it makes these sorts of playback problems better—and sometimes eliminates them almost completely.

To see what I mean by those comments, try putting on the Civil Wars’ Barton Hollow CD [Sensibility] and listen closely to the upper register of Joy Williams’ voice. My past experience has been that, on this generally well-recorded album, the top of Williams’ range can—at full song—exhibit faint but audible traces of strain and momentary patches of a subtly grating, rough-textured quality (it doesn’t happen often, but it’s annoying and musically disturbing when it does). Through the PS Audio DAC, however, the performance envelope of the album seems almost to stretch out, allowing room for Williams’ voice to soar up high and at elevated levels, but without being marred by audible stress, strain, or bursts of break-up. This is precisely the sort of sonic forward progress you can expect to hear over and over again with the DirectStream DAC.

Because the DAC is very quiet and does a great job of retrieving low-level details—especially small, evanescent spatial cues—it can take ordinarily flat-sounding recordings and suddenly give them a heightened sense of body, shape, and depth. This quality of three-dimensionality, along with the DAC’s delightful (albeit improbable) marriage of high resolution and unforced graciousness, is what really defines the sound of the DirectStream DAC for me.

Having praised the DAC for its resolution, smoothness, three-dimensionality, and grace, you might draw the inference that it is highly forgiving of imperfect recordings, but in my experience that really wasn’t the case. The DirectStream DAC will improve what it can about mediocre recordings, but it nevertheless exposes them for exactly what they are. What is more, because the DAC tends to clean up whatever it can in so-so recordings, those sonic problems that can’t be ameliorated tend to stand out in even sharper relief. While the DirectStream DAC can make good, very good, and great recordings sound better than ever, it cannot and does not compensate for poor or mediocre recordings. In the end, the sonic truth will out.

PS Audio’s DirectStream DAC turns the established order of things in the PCM-centric digital audio world upside down and it sounds all the better for it. I have greatly enjoyed my time with the DirectStream DAC, in no small part because it has demonstrated the sonic benefits of a fundamentally different—and perhaps fundamentally superior—method of playing both PCM and DSD digital audio files. For this reason alone I would encourage readers considering DACs in this price range to give the DirectStream DAC a very careful listen. If your reactions are anything like mine, you may find yourself won over by the fresh musical insights this DAC makes possible, even on recordings you once thought you knew well.


PS Audio PerfectWave Transport

As mentioned above, the PerfectWave ‘Memory Player Transport was originally conceived as the companion to the original PerfectWave DAC—the precursor to the DirectStream DAC reviewed here. Interestingly, though, all three components share a common physical form factor and were designed so that they can be stack atop one another.

, PS Audio PerfectWave disc transport/DirectStream DAC (with Pikes Peak OS)

The PerfectWave Transport comes from an era when computer-based music servers were not as common as they are today, and when DSD digital audio files were rarely if ever discussed. What PS Audio sought to create was a CD/DVD disc reader/transport that anticipated the sonic benefits of contemporary music servers.

To this end, the key idea behind the PerfectWave Transport was that it would not play digital audio data directly from discs, but rather from a 64MB buffer, which PS Audio termed a ‘Digital Lens’. PS Audio states, “It is the fact that you are listening to the stored version of what’s on the disc that helps the music sound so lifelike and spacious.”

Thanks to this buffer memory, the PerfectWave Transport’s DVD disc drive mechanism has ample time to use what PS Audio describes as “a multiple read technique, which reads the data on the disc until it’s verified as bit perfect.” What is more, the digital audio data is fed into the Digital Lens with, “no clock information attached to (the files).” Instead, the output of the Lens is, “forwarded to the PWT output though a fixed high‑precision, low-jitter asynchronous clock.”

As a result, the sound quality associated with playback of data from the PerfectWave Transport is fully competitive with that of playback from a well-sorted modern day, PC-based music server. In fact, if anything, the PWT might enjoy a very narrow edge in terms of resolution of low-level musical information. The PWT can read CDs or DVDs on which PCM-format digital audio data (at resolutions up to 192/24) has been stored; the PWT does not, however, play Blu-ray, DVD-Audio, or SACD discs. Even so, the PerfectWave Transport makes a worthy companion to the DirectStream DAC—especially for listeners with very large CD collections.


PS Audio PerfectWave Memory Player Transport

  • Type: Solid-state CD transport with memory playback
  • Disc Types: CD, DVD-ROM with WAV-encoded PCM digital audio files at up to 192/24 resolutions, or DoP-encoded DSD files (note: does not play DVDs, DVD-Audio discs, or SACD discs)
  • Internal storage: 64MB ‘Digital Lens’
  • Digital outputs: TOSLink, coaxial S/PDIF, AES/EBU, and I2S
  • User interface: PS Audio remote control plus on-board full-colour touchscreen controls
  • Dimensions (HxWxD): 10 × 42 × 36cm
  • Weight: Approximately 12.2 kg
  • Available finishes: Silver or black
  • Price: £2,999
  • PS Audio DirectStream DAC
  • Type: Solid-state PCM, DXD, and DSD-compatible DAC
  • Digital Inputs: Two I2S, coaxial S/PDIF, TOSLink optical, AES/EBU, USB, and Network bridge slot
  • Supported Formats: PCM: 44.1kHZ–192kHz, 16–24 bit. DSD: DSD64 and 128
  • Analogue Outputs: Single-ended (unbalanced) via stereo RCA connectors, balanced stereo analogue via dual 3-pin XLR connectors
  • Frequency response: 20Hz–20kHz ± 0.25dB
  • Distortion (THD + Noise @ 1kHz, full scale): <0.03%
  • Output voltage: Two user selectable settings:
  • Low output setting: 1.41 Vrms (+5dBV)/3.15
  • High output setting: 2.81 Vrms (+8dBV)/5.3Vrms (+12dBV)
  • User Interface: PS Audio remote control plus on-board full-colour touchscreen controls.
  • Dimensions (H×W×D): 10 × 42 × 36cm
  • Weight: 13.5 kg
  • Available finishes: Silver or black
  • Price: £5,250, or £5,550 with optional Network Bridge module installed

Manufacturer: PS Audio

URL: www.psaudio.com

UK Distributor: Signature Audio Systems

Tel: +44(0)7738 007776

URL: www.signaturesystems.co.uk


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