First Listen: PS Audio DirectStream DAC with Pikes Peak operating system
This blog is not a full-fledged Hi-Fi+ review, nor should it be read as one. Instead, it is – as the title states – an introductory ‘first listen’ to PS Audio’s unique, impressive, and newly upgraded £5,250 DirectStream DAC (or to £5,550 with the optional Perfect Wave Bridge module, which our sample did not include). The DirectStream DAC also includes the firm’s latest Pikes Peak operating system.
PS Audio’s digital line is not confined to DACs, and in a week or two, I will be doing a follow-up blog on another PS Audio product commonly used in conjunction with the DirectStream DAC: the PerfectWave Memory Player (also known as the PerfectWave Transport, or PWT). Like the DirectStream DAC, the PWT has some interesting and unconventional technical features, so that my thought is that the PWT deserves a separate blog of its own (stay tuned).
With the advent of higher resolution PCM-format digital audio files and increased interest in DSD, DACs and universal disc players that handle DSD files by converting them into PCM are relatively commonplace. This approach makes sense for some DAC makers—especially those whose primary expertise and technical ‘comfort zones’ centre on working with PCM files.
PS Audio, however, takes precisely the opposite approach with its DirectStream DAC, which instead converts all incoming digital audio files to DSD format, upsamples those files to 10x DSD speeds, and processes them using what the company terms a, “true single-bit, double rate DSD core engine.” The resulting circuit path offers what PS Audio describes as, “advantages in simplicity, linearity, and in analogue-like overload characteristics that avoid PCM’s ‘hard clipping’ and propensity to mask subtle details.”
PS Audio appears firmly convinced that DSD is a fundamentally superior format as compared to PCM and that part of its superiority involves the inherent simplicity of the circuits involved. As a PS Audio position paper puts it, “the output of a DSD stream can be placed through a simple filter to produce pure analogue ready to feed your audio system,” where PCM, “can produce great sounding music, but to do so requires a very complex and technically daunting conversion process to produce something you can play on your system.”
The company didn’t always think this way. The DirectStream DAC’s immediate predecessor was PS Audio’s decidedly PCM-centric PerfectWave DAC, a very sophisticated and critically acclaimed device in its own right. However, according to PS Audio, listening sessions conducted during development of the prototype for what eventually became the DirectStream DAC convinced the firm that a DSD-centric DAC offered greater performance potential, a more musical sound, and a better way forward. To PS Audio’s credit, the firm developed a set of replacement circuit boards that allow PerfectWave owners to upgrade their units to the new DirectStream DAC circuitry, if desired.
Everything about the DirectStream DAC follows PS Audio’s ‘simpler sounds better’ philosophy. The DAC uses a purely passive transformer-based output stage, where the transformer is driven by “high speed Class A video amplifiers” that serve as the “final switch for (the DirectStream DAC’s) single-bit double-DSD output.” By design, the transformer provides, “galvanic isolation between the DAC and the outside world,” and it also serves double-duty as, “the primary low pass filter required to present a perfect, low distortion, low noise output signal.” According to PS Audio, the upshot of all this is that, “When you listen to DirectStream you are never accosted by added bright, hard glare in the music as happens with many active designs.”
Great care was also taken to minimise jitter: unlike conventional DACs that often use multiple master clocks for different sections of their circuitry, the DirectStream DAC instead uses just one low phase noise, low-jitter master clock designed by frequency control experts Crystek – a clock that is said to be “of extraordinarily high quality.” This approach eliminates the problem of having to synchronise multiple clocks with one another, while minimising differences in sound quality between various source devices – especially differences caused by some sources having different amounts of jitter than others. While conceding that, “cables and sources still make a difference,” PS claims that “with DirectStream that difference is reduced to nearly background noise.”
PS Audio President Paul McGowan says that the DirectStream DAC uses, “a custom and complex operating system, similar to that running your computer,” so that it makes sense to call these Pikes Peak software revisions, “what they truly are: an operating system update.” The OS update processes are complicated: DirectStream DAC’s designer, Ted Smith, prepares 20 compiles of the new OS (along with compiles of matching PIC code) for evaluation and sends them to a very special member of the PS Audio team – legendary loudspeaker designer Arnie Nudell. Nudell carefully selects the three best OS compiles and matches, “them to the best of the PICs to voice the final product.” This final set of three OS/PIC packages is sent to McGowan, who works closely with Nudell to make the final selection for release to the public.
Since its inception, the DirectStream DAC has gone through three software updates, each of which was said to produce audible improvements to the DAC’s sound. But significantly, both the team at PS Audio as well as members of the DirectStream DAC user community say the new Pikes Peak OS yields larger and more dramatic improvements in sound quality than any previous updates.
Since the Hi-Fi+ sample of the DirectStream DAC came with the Pikes Peak OS already installed, we aren’t in a position to comment on how the DAC might have sounded with its earlier OS iterations. However, PS Audio President Paul McGowan is understandably extremely enthusiastic about the new OS:
“The new Pikes Peak OS is extraordinary. Both Arnie and I find it to be a greater jump in sound quality than the last major release we did at the end of last year (DirectStream 1.2.1). Pikes offers far better body of the instruments, an extended top end, firmer bass, and a soundstage that will make you swoon. This upgrade is huge. And it is free to all DirectStream owners.”
The DirectStream DAC features six digital inputs: AES/EBU, coaxial S/PDIF, TOSlink, USB, and two I2S. In turn, the DS DAC provides two stereo analogue outputs: single-ended (via RCA jacks) and balanced via XLR jacks. It is also possible to order the DirectStream DAC with an Ethernet-capable ‘PerfectWave Bridge’ board installed, although the review sample does not have this option.
Up front, the unit features an operate/standby switch and a moderately-sized, responsive, full colour touchscreen display that shows the DAC’s operational status at a glance. A useful remote control is provided, so that users can control the DAC without having to use the touchscreen control panel.
Under normal circumstances, the display shows a considerable amount of detail about the input selected, including file format, sampling rate, bit depth, the absolute phase setting chosen by the listener, and the volume level of the DAC’s analogue outputs. In units where the PerfectWave Bridge is installed, the DAC will also access the internet to look up the album artwork for any recording you choose to play and will store that data on an included SD card. Thereafter, the display screen will automatically show the album art whenever the same recording is played.
While the DirectStream DAC can, of course, be used in conjunction with a preamplifier, PS Audio strongly recommends connecting the DAC directly to the system’s power amplifier(s), which is how we have been using the DAC thus far. As PS Audio’s pundits are fond of saying, there is no sound quite like the sound of “no preamplifier at all.”
Kevin Akam of Signature Systems, PS Audio’s UK distributor, advised us that the DS DAC would need plenty of run-in time before fully coming on song, but the DAC sounded pretty impressive straight out of the shipping carton. From the very start, I found the DirectStream DAC was one of the least ‘digital sounding’ and most ‘analogue-like’ digital audio devices I’ve encountered in a long while.
Here’s what I mean:
When discussing digital audio’s ‘dark side’, somewhat paradoxically I usually think of a host of small, unpleasant, overly bright, and unwanted sonic artefacts that together impose upon the music a subtly cold, glassy, sterile, hard-edged, brittle, or mechanical quality. The resultant sound just doesn’t allow recorded music to breathe and flow the way that live music does. If you ever get the chance to do so, it is instructive to visit a recording studio where musical tracks are simultaneously captured in both PCM digital and analogue formats (typically on analogue master tapes). If you step out of the control room (with the engineer’s and musicians’ permission, of course) to hear the live music as performed in the studio space, then come back into the control room after the take is completed, you can hear easily how the digital and analogue recordings compare to the real thing.
When I have tried this, I’ve found the digital masters tend to sound quiet and pure, but slightly bright and edgy, with an almost hyper-accentuated vividness that, though appealing in its way, really doesn’t sound like the live performance. It’s somewhat like the difference between seeing a gorgeous butterfly in flight in open sunlight and seeing one pressed flat under a plate of thick glass under intense, museum lighting; the colours are still there after a fashion, but the life has simply gone out of the poor thing. The trite analysis might be to say, “something got lost in translation” with the digital recording, but I suspect the sonic truth is more likely that something unwanted got added in translation.
Analogue master tapes, on the other hand, obviously exhibit more background noise than the digital format, but otherwise sound – to my ears at any rate – markedly more like the real performance. Sonic details and timbral purity are both fully present and accounted for, but – and this is the part that’s so hard to achieve – they present themselves in an utterly natural, unforced, and unexaggerated way. Similarly, dynamics ebb, flow, and breathe just as in real life and if things happen to get really loud, the format handles temporary overloads gracefully, rather than exhibiting the harsh signs of dreaded hard clipping.
I mention this comparison because PS Audio’s DirectStream DAC shows, even in these early days, a tendency to sound like really good analogue tape playback, but without any tape hiss or other background noise. And so far, it appears that McGowan’s assessment is spot on: the DAC’s top end is airy-sounding and capable of resolving fine, feathery, filigreed treble details, while the low end is rock-solid and possessed of a distinct taut snap and bounce (assuming those qualities are in the recording in the first place). Soundstaging, too, is already pleasingly three-dimensional, and shows signs of gradually becoming even more impressive as run-in time accumulates (though of course only time will tell).
My initial finding is that PS Audio’s DirectStream DAC shows considerable sonic promise: it already sounds unexpectedly accomplished, and it’s likely the running in process will only build on that early accomplishment. It will be very interesting to see how the DAC is sounding, say, a month or two from now, but I am hoping for very good things.
Watch for our upcoming Hi-Fi+ review of the DirectStream DAC and, until then, happy listening.