Digital Processor Reviews

Ayre Acoustics' CX-7e CD player came on the market in 2002. I bought one in 2007, and enjoyed its smooth, musical sound, which in 2009 was further advanced by the MP upgrade.

Time passed. The high-resolution disc formats of DVD-Audio and SACD failed to catch on, and I stayed with CDs. Then came hi-rez downloads and streaming. I stayed with CDs. Now we have the apparent rebirth of DSD, the codec used for SACD, as a download format—and there's PonoMusic, with the promise of a hi-rez format for the masses. I'm staying with CDs—and, of course, LPs. The music I like is mostly unavailable in hi-rez formats, so I have no incentive to invest time and money in equipment that can play them. I'm also resistant to using the computer as a music source.

However, I've had a CX-7e^MP for five years now, and although it's performed well, over the past year it's developed an intermittent problem: a mechanical purring sound made by the transport. This initially showed up with only certain discs, which made me think that the problem was with the discs themselves. Then the purring began to occur with other discs, and more frequently. Although there was no obvious degradation, there could have been some subtle deficit that I wasn't hearing. I could send the unit back to Ayre for repair, but that could take a while—and I was in the middle of evaluating GoldenEar Technology's Triton One loudspeaker. Although I prefer to avoid changing any part of my system when a review is already under way, it wouldn't be fair to any speaker to review it with a CD player that was possibly not working properly.

Then there was the urge to upgrade—familiar, I'm sure, to all Stereophile readers. Maybe my problem with the CX-7e^MP was a sign that I should consider getting a digital source that incorporates the improvements in digital playback technology that have occurred since the CX-7e^MP was introduced. One product that particularly intrigued me was PS Audio's PerfectWave DirectStream DAC (which I'll call the DS from here on). I was struck by the claim, made by PSA's CEO, Paul McGowan, that the processing done by the DS—which converts all digital signals to DSD before converting them to analog—results in superior playback of CDs. As McGowan says in a video introducing the DS, "What if, on your CDs, is a lot of information that you didn't know was there?" What if, indeed?

I'd read the highly positive reviews of the DS by Art Dudley and Michael Lavorgna, but Art and Michael each used a computer as the source, not a CD transport, and their emphasis was on the playback of various hi-rez recordings. (Of course, they also played CD-standard, 16-bit/44.1kHz computer-audio files—just not CDs.)

I had to check this out for myself. A local PS Audio dealer kindly lent me for a few days their demo units of the DirectStream DAC ($5995) and its companion, the PerfectWave Memory Player CD/DVD transport ($3995, hereinafter called the PW). (Thanks to Francis Chung, of Toronto House of Audiophile.) Two days' experience with a product is not enough for a review, but it was long enough for me to conclude that there was something special going on with this DAC and transport. I asked PS Audio to send both a DS and a PW, and they arrived in about a week.

But before making any comparisons between the Ayre CD player and the PSA combo, I had to get the CX-7e^MP fixed. I got in touch with Charles Hansen at Ayre, who said that I should send them the unit; they would replace its transport. I sent the CX-7e^MP to Ayre's service department and settled down to listen to the DS and PW.

No sooner had I sent the CX-7e^MP on its merry way than the PW stopped working. Its video display was on, so it wasn't a matter of a blown fuse, but the transport refused to release the CD it had just finished playing. The recommended remedy of turning off the power and turning it on again didn't work; the video display indicated that the PW was initializing, but it would neither play nor eject the disc. I used the "emergency eject" procedure described in the manual—a paper clip is required—and the drawer opened. I removed the CD, which was not obviously defective in any way, but the drawer then refused to close, with or without a CD.

I sent an e-mail to Paul McGowan, who said that this problem was highly unusual; in fact, their service department had not encountered it before. He said that they would ship me a new unit the same day, and that I was to return the broken one. The replacement arrived a week later and worked fine. Not only did it play all CDs without a hitch, it was absolutely quiet—unlike the first sample, which had made some mechanical noise (though not the loud purring that had afflicted the Ayre) when playing discs.

And the sound of the DS-PW? In theory, the sound reproduced from a CD can't be more detailed than is encoded in the pits and lands of the CD itself, and which represent the binary information of the recording—and even modestly priced CD players are usually bit-perfect at retrieving this information. And yet, listening to familiar recordings, recent as well as some from the early days of CD, I heard more musical detail from them than I previously had. This detail was not a matter of exaggerated treble, which can give an impression of increased detail, but was genuinely higher resolution manifested by greater differentiation among the sounds of instruments and rhythmic patterns. For example, in Clark Terry's performance of "Pennies from Heaven," from the Chesky Records Jazz Sampler & Audiophile Test Compact Disc, Vol.1 (Chesky JD37), before using the DS-PW I'd been only vaguely aware of the sound of Victor Gaskin's double bass in the background. With the DS-PW, the instrument wasn't obviously louder—which could have been due to a bump in the frequency response in that part of the range—but was presented as a more three-dimensional aural image that more clearly differentiated the sound of the bass from the other instruments.

To further test Paul McGowan's claim of CDs having "a lot of information that you didn't know was there," I dug out some of the discs I'd bought back when most record stores' CD section was a single, small rack. I remember buying orchestral recordings early in the digital era and being disappointed that massed strings sounded like mush. One of these was a 1986 recording of Dvorák's Symphony 9, with Christoph von Dohnányi conducting the Cleveland Orchestra (Decca 414 421-2), whose CD booklet bears a banner proudly proclaiming it a "Digital Recording." The strings sounded like a synthesizer.

That was before the DS came into the picture. Presented the same sequence of zeros and ones, the DS was able to reproduce sounds that were more plausibly the result of real instruments being played by real musicians, with better differentiation among instruments. Quite amazing.

Optimizing the DirectStream DAC: The first way to optimize the performance of the PS Audio DS—and, alas, the only one that's free—is to give it enough break-in. Out of the box, the DS sounded quite dull. This was the unit sent by PS Audio, not the one I'd earlier borrowed from the dealer, which had been thoroughly broken in. So I put a CD (one of Reference Recordings' orchestral recordings) on repeat, and left the DS on but turned off the power amplifier, a McIntosh Labs MC275LE. When I listened to the system 12 hours later, it was clear that the sound had improved quite a lot; but based on what I'd read about break-in with the DS, I thought it likely that further improvement was possible—and indeed it was. The DS seemed to hit its stride at around 400 hours, revealing more detail in complex instrumental textures.

The DS has a good range of digital inputs, but the two that are of particular relevance to optimizing sound quality are HDMI and AES/EBU (XLR). PS Audio uses the HDMI input in a nonstandard way, turning it into an I²S connection, which separates the clock and datastream signals, and is what PSA recommends for best sound.

I tried a length of Nordost Blue Heaven HDMI cable ($320); PSA sent along one of their own HDMI-10 cables ($350), and Nordost provided a length of Valhalla 2 AES/EBU (XLR) digital cable ($3200). The Valhalla 2 XLR sounded best, with the greatest clarity and the best imaging. However, PSA's HDMI cable wasn't far behind. The Nordost Blue Heaven HDMI, for which I had high hopes, wasn't as good as either. (I also tried a generic HDMI cable that cost less than $10; it was pretty bad.)

PS Audio recommends using high-quality aftermarket fuses; I use, and have written about, HiFi Tuning Supreme fuses. I installed one each in the DS and PW. (Each component has two fuse bays, but PSA told me that only the fuse in the F1 bay need be replaced.) Replacing the fuse requires removing the top of the case—no task for the fainthearted. I managed it for the DS, but the PW refused to open; it took Ronald Hung, Toronto Home of Audiophile's highly competent and very patient technician, more than half an hour to do the job. It was worth it: with the HiFi Tuning Supremes, the DS-PW combo ascended another rung of clarity. At $100 for two fuses, the improvement was a bargain.

The final decision had to do with the analog output: Since the DS's analog output is variable, it can be used to drive an amplifier directly rather than running the signal through a preamp. Like most people who've compared a high-quality active preamp with a passive controller, I've found active preamps to be superior, particularly in dynamics. But the DS is different: its output level is controlled in the digital, not the analog domain, and Ted Smith, lead designer of the DS, claims that using the DS's variable output to drive an amp directly results in no loss of resolution. In fact, this is what PSA recommends for optimal sound quality.

Listening at matched levels through my Convergent Audio Technology SL-1 Renaissance preamp vs direct connection, I went back and forth at least a half-dozen times, trying to decide which was better—which should give you an idea of how close the sounds were. The sound through the CAT was a bit warmer, which was welcome with voices. The direct connection to the MC275LE resulted in even more finely defined detail, but perhaps veered slightly in the "clinical" direction. Overall, I preferred the connection through the preamp, but it was a close thing. The CAT is one of the best preamps around; pitted against a lesser preamp, the direct connection would likely be the winner.

Compared with the Ayre Acoustics CX-7e^MP: My CX-7e^MP was returned to me a week or so before the review of the PS Audio gear was due, so I was able to make some comparisons.

Ayre had replaced the purring transport with one that was absolutely silent. Played on its own, with no comparisons with any other digital source, the CX-7e^MP sounded just fine. It didn't have the digital edge that less-refined CD players are prone to (I used the Ayre's Listen rather than its Measure filter), and I do believe that it sounded somewhat better than with its purring transport.

However, compared with the DS-PW (by this time I was using the DS's latest firmware, v.1.2.1; see "New Firmware," below), there was no contest: the DS-PW simply communicated more detail, with more three-dimensional images and more finely nuanced microdynamics. The PSA combo costs $9990 compared to $3500 for the Ayre, so it should sound significantly better—and it did. I could easily live with the Ayre CX-7e^MP—but having heard what the PS Audio combo can do, I don't want to.

What about the PerfectWave? This is a Follow-Up on the DirectStream, not a review of its matching transport, so I won't say much about the PerfectWave Memory Player. I'll assume that the first sample's mechanical noise and subsequent demise were a matter of sample variability—and audio manufacturers know that if anything is to go to wrong with one of their products, it's going to be a sample sent to a reviewer! The second sample worked perfectly and was absolutely quiet. The PW's design—it reads and rereads the disc's data until it's bit-perfect, and uses a substantial buffer so that the DAC is sent data relatively free of jitter—sounds very sensible to me, though some may argue that it approaches overkill. SACD fans will be disappointed that the PW doesn't support the format.

I had a chance to compare the PW with the digital output of the repaired Ayre CX-7e^MP (both AES/EBU, Nordost Valhalla 2 digital cable, both feeding the DS with the latest firmware). I expected any difference to be marginal at best, but that's not what I heard. The PW seemed to act synergistically with the DS, enhancing the latter's ability to retrieve the maximum amount of sonic information, and sounding even less "digital" in the process. The PW is a well-thought-out, well-performing product; for anyone buying the DS, pairing it with the PW is the safe way to go. However, the cost is not negligible; if you already have a high-quality CD player with a digital output, it makes sense to try to borrow a PW to hear how it compares.—Robert Deutsch