Back in the day, and by back in the day I mean the 1990s, more than once I would be lent a CD player with a vacuum tube output stage. Many of these were DIY modifications, some were not. Even though these designs resulted in something that I'd wouldn't want to listen to on a long term basis, it wasn't difficult to hear why some would add tubes to the output stage of a CD player. In those days CD playback was in need of serious help. Most CD players were barely listenable, so at that time the only benefits they had over the LP were their silent background and convenience, yet in the majority of cases at the very least these tubes added to the output stage made CD playback give me less of a headache. When vacuum tubes were added to these older CD players they were used in large part as filters to protect our ears from the players harsh upper-midrange and steely treble that was endemic to these players, but in the majority of cases the problem was that adding tubes to the player's output stage only added another layer of circuitry that confused the signal and thus the music, and made the signal far less transparent. There were many problems with these older players that had not yet been addressed, offenders such as jitter was just one of the problems that haven't yet been properly identified, and were rarely dealt with. These days, CD playback (often called digital playback in my listening room) has come a long way. And that is a huge understatement.
PrimaLuna manufactures tube products, CD players included. But PrimaLuna is not using tubes in their ProLogue Premium CD Player as an attempt to cover or "fix" anything. PrimaLuna is a perfect example of a company that manufactures components that use tubes that do not have a "tube" sound in the classic definition of the word, instead PrimaLuna uses good engineering sense to exploit the benefits of vacuum tubes with very, very few of their disadvantages. PrimaLuna's most recent foray into CD playback was their ProLogue Eight (now called the ProLogue Classic), which was very well received by the audiophile press and customers alike. PrimaLuna has taken this design to the next level, with a significant number of upgrades. Plus, very importantly, the ability to connect one's USB cable to the player's internal digital-to-analog converter.
The Premium (as I'm going to call this component from this point forward) is a based on a dual-mono design, and PrimaLuna claims that it is the first CD player to use dual vacuum tube rectification. They adapted the power supply from their rather popular ProLogue Premium preamplifier, and is built using "high quality" (one would hope) resistors, MOSFETs, and Solen capacitors to for "superior transient response, detail, and channel separation". The output stage of the Premium is dual-mono, using one 5AR4 rectifier tube and two 12AU7’s per channel, and uses a "state-of-the-art" Burr Brown 192kHz/24-bit upsampling circuit as well as a Burr Brown DAC chip. Other "premium" (ahem) parts of the Premium include polypropylene coupling capacitors and triple pi power supply filters (these are also called capacitor input filters), plus, the player's analog and digital devices are separated by custom designed isolation transformers. Included in the price of the Premium is their Super IV op-amp, which was at one point available only as an option in many of PrimaLuna's components.
The ProLogue Premium's USB input will be of interest to many listeners including Yours Truly. In my listening room as well as in the second system in a common space of the house, the large majority of the digital tunes come from a music server. PrimaLuna says that the USB input that is accessed on its rear panel was hardly a design afterthought. After researching many interface options they decided on using the hiFace made by the Italian audio manufacturer M2Tech. Enjoy The Music readers are likely to recall the praise this small piece of equipment received in its review in the February 2010 issue. PrimaLuna goes on to say that this USB input converter drastically reduces the amount of jitter even before it reaches the Premium's SuperTubeClock. The Premium's USB input is capable of decoding a digital signal of a sample rate of up to192 kHz with word length of 24 bits.
The PrimaLuna's M2Tech USB interface gave me a leg up on the set-up of the use of the USB input. M2Tech recommends one use kernel streaming on the output settings of the host computer. Since I had just reviewed the M2Tech Vaughan DAC in the March issue, I knew to set my Foobar 2000's preferences to kernel streaming using the hiFace's driver. Kernel streaming has the advantage over the more common direct streaming because when playing back files they do not pass through Windows or Mac operating system's audio mixer, so the native sample and bit rates are more likely to be preserved. My music streamer is set up on a PC, a 3.20 GHz Dell Studio XPS PC with 8G RAM running Windows 7. A gaggle of FLAC files are stored on three different external hard drives, and a run of DH Labs Silver Sonic USB cable connects the computer to the Premium's USB input.
The Premium is certainly larger (and heavier) than most CD players or DACs. At nearly eight inches tall it is going to need a bit more shelve space. Plus, the tubes need room to breathe. It doesn't need as much space as a tubed power amp, because the tubes aren't at large as most power amps so they don't get nearly as warm. Still, I placed the Premium on the second the top shelf on my Arcici Suspense rack with more than three inches of space above it. The Arcici does not have back or side panels, so heat was never an issue.
On the simply laid-out rear panel's IEC power cord outlet I used a Virtual Dynamics power cable for a short time, but finally settled on an Audio Art Statement II for remainder of the review. The analog outputs of the Premium are unbalanced RCAs, I used a pair of either MIT 330 Plus or Audio Art IC-3 SE interconnects to connect it to a Balanced Audio Technologies (BAT) VK-3iX tube preamp, with the preamp's XLR outs wired with MIT Shotgun S3.3 balanced interconnects to a Pass Labs X350.5 power amplifier. For the current hungry amp I used an Audio Art Statement I power cable for the beginning of the review, and a Virtual Dynamics cable for the remainder. The speakers are Sound Lab Dynastat hybrid electrostatic panels along with a Velodyne HGS-15b sub. All the front end equipment, including the PrimaLuna Premium CD, was connected to a PS Audio Power Plant AC regenerator. The speakers and subwoofer were connected to a Chang Lightspeed power conditioner. The room is treated with Echobuster acoustic treatment panels and filled LP and CD shelves. Since I've been very busy lately, room is in need of a good tidying up.
Regardless of what I said above, I'm not about to deny that tubes are likely the cause of the player sounding different that the other fine pieces of digital gear in my system, but it is certainly a surprise that it sounds better than this other gear given the track record of tube-based output sections of the digital components I've heard before. But let's be real: those tube-based output sections weren't designed by PrimaLuna in 2013.
I wish it were possible to direct one to a single
musical example, or at least one track that is a perfect demonstration of the
Premium’s prowess with a digital signal. I can't, only because there wasn't
any music that I played through the Premium that didn't demonstrate the unit's
strengths. To describe the Premium's sound is to describe the sound of excellent
vacuum tube gear, that is, with all the advantages of tube sound without any of
the advantages, but in this case as applied to digital playback. When a
layperson (in other words, a non-audiophile) describes why they sometimes don't
like CD as opposed to LP playback, many claim that the sound of CDs are "flat"
sounding, or "harsh". I don't think that any of the modern CD players or DAC
that have passed through my system in the last decade or so can by any stretch
of the imagination be described as possessing these negative traits, but when
these machines are directly compared to the Premium, these characteristics come
to fore. No, I wouldn't describe the sound of the Wadia 121 Decoding Computer as
harsh, but I would consider its upper mids and lower treble as harsh-er
when directly compared to the Premium.
I wouldn't in any way call the dynamics of the M2Tech Vaughan as "flat".
In fact this unit has the best soundstage of any DAC I've ever heard in my
system! But compared to the dynamic distance that the Premium puts between two
instruments playing at the same time at the same volume as being more separated
in its sonic field of view, and thus the Vaughan's dynamic distance sounds flat-er.
As is the case with most system's response to DACs vs. physical CD playback, the Premium demonstrates that yes, playing the music through the USB input of the Premium provides all the advantages of hard-drive playback, but in this case one can compare the two directly using the exact same electronics, minus the CD drive, yet plus the hiFace digital interface. Very nice! On the CD of Keen Bakels conducting the Bournemouth SO in Vaughan Williams 7th Symphony (Antarctica) on Naxos, it was practically a showpiece for the Premium's ability to reproduce a Red Book symphonic CD. The symphony's last parts are best known for its deep organ tones, but was immediately noticeable was the metallic percussion used in the score, which includes cymbals, triangle, gong, bells, and xylophone, and it seems that at least half of those listed were being used in the back row of the orchestra in the beginning of the fifth movement. The Premium was able to reproduce the acoustic of Wessex Hall's rear wall as well as the instrument's direct sound, of course, reflecting the sound of those instruments towards the listener. The instrumentation builds throughout the movement, demonstrating that the CD player's sound with the disc in the drawer is certainly an acceptable substitute for hooking up a USB cable. Not that the USB playback is bettered, but at least one is not disproportionately punished for playing physical media.
If my praise of the Premium lends one to believe that it is the "perfect" CD player or DAC, think again. Yes, the sound it produced in my system is wonderful and extremely close to the best digital sound that I could imagine at this point in digital's relatively early history. And given PrimaLuna's history of producing gear with an amazing price to performance ratio, the Premium fits right in. But at the same time one should consider exactly what this component is: a CD player with a USB input.
System matching can and should also be considered, as well as what one's listening habits are at present and in the foreseeable future. There are some that might have darker sounding associated gear that might find the sound of the Premium as too much of a good thing, so those with systems leaning to this less resolving characteristic in the first place will not be able to take advantage of the Premium's less aggressive sound when compared to most other digital playback gear. There are also others that might want more than just a USB input enabling them to hook up other disc transports, etc., to the Premium, and so we are again back to the subject of system matching, and I don't think anyone would recommend someone change their entire system or complete change their listening habits to accommodate a single piece of front-end gear. Also, there is the relatively minor fact that the Premium's display does not display the resolution of the incoming digital signal when listening through its USB input, and if this bothers them they might want to investigate on-screen options for one's server if that bothers them. Added to all this, there might be some audiophiles out there that shudder at the thought of using a piece of tube gear as a digital playback device, not willing to make space on their shelf for the hotter running, larger than usual cabinet of the Premium, and perhaps not willing to purchase another piece of gear for DVDs, SACDs, etc. To those folks I say: Your loss. The PrimaLuna Premium is a fantastic piece of digital listening gear, and if one has to "adapt" to its unique looks or operation, then so be it. Recommended? You bet.
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