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However, it's not only Polish albums which suffer from this type of illness. Listen to Abba and you'll hear the same thing. The disco target of most their recordings, short production deadlines as well as a fairly relaxed attitude about sound quality meant that most albums by this Swedish quartet and winners of the 1974 Eurovision Song Contest sound horrid no matter what treatment they underwent or how they were released. As usual vinyl issues are privileged in this respect. Even the SHM-CD version sounds light and lifeless. The difference between the latter and well-produced CDs is usually dramatic but much smaller on the CD9. It makes for a pleasant listen to standard CD without forced attention on mastering errors or recording chicanery.

There are other albums that sound exceptional on the ARC. Generally each disc played very well but some actually got a new lease on life. So it was with Sting’s The Dream of the Blue Turtles and a few Dire Straits albums, especially Brothers in Arms. The former was recorded on analog equipment, the latter on digital yet both sound somewhat flat and lifeless on CD. I have their best digital releases I know of—Sting on Mobile Fidelity, Dire Straits on SHM-CD XRCD2—yet some things just cannot be overcome. Played back on a regular CD player they will sound correct, perhaps even good. Just as it had previously with the Polish discs, the American unit brought out what’s best in them: fantastic arrangements, color and complex textures. It mostly benefited the guitars but the bass (which was understandable) and drums also sounded meaty.

Digital files. My description of the Audio Research Reference CD9 player won't be complete if I didn't say anything about its playback of audio files especially via USB. The machine played CD rips or Redbook files downloaded from Linn Records, Naim Label or HDTracks very similar to CDs but ultimately I preferred the physical media. While USB provided a deep and warm sound, the CDs were slightly more open and resolving which happened to be of value. After all it is a Compact Disc player. The difference wasn't striking though. If someone had a large collection of CD-quality recordings on the hard drive, they'd be a joy to listen to. What’s more, MP3 files too were very nice. Here we have reached the gutter. Bouncing back towards the stars with high-res files immediately rides on rising currents. With this type of signal the CD9 was not only vivid and dense but tonally more linear as though hi-res files didn’t need the additional support of stronger bass. In absolute terms the difference between physical discs and hi-res was not large enough to talk of a qualitative leap. The reason that physical media sounded so convincingly good was that the better depth, more balanced frequency response and slightly clearer treble of 24-bit data did not turn anything upside down. They however had their own value.

Digital filters and upsampling. Like any high-quality digital source, the Audio Research player offers the capability to shape its sound. This is limited and nothing extravagant but available. First off you can use upsampling. This technique was first introduced in the 1990s to immediately gain immense popularity. In a short time components without it were treated as defective. In retrospect we can see why. In theory each component in the signal path introduces distortion. So it is with digital circuits. However sometimes it is worth to sacrifice one thing to get another. The additional component that became any DAC’s integral part was the upsampler. Its role was to convert the input sampling frequency from 44.1kHz for CD or 48kHz for DVD to 96kHz, then 192kHz (for asynchronous upsamplers). The upsampler also extended word length from 16 to 24 bits. This was something of an extra function. After all it’s a sample rate converter and the name obliges. The sound quality improvements resulted from two things, one of which used to be considered major (also by me) whilst the other was usually passed over in silence. The first was to feed the DAC a pre-processed signal with the highest parameters it could handle. That way the DAC was spared the additional internal processing carried out by the preceding circuit. The second issue related to jitter. Upsampling, be it asynchronous or synchronous, consists of signal reclocking. It seems that actually this was the main value of upsamplers. Reclocking improved signal precision and reduced jitter.

Pretty soon the problem of signal clocking was widely noticed and given a lot of attention with separate oscillators for the two sample-rate families, their own dedicated power supplies and other techniques. A player without high jitter reacts to upsamplers differently than other players. In addition to the above the Ref CD9 features a separate digital filter that reclocks signal for a very low 10ps jitter. Hence switching in the upsampling changes rather than categorically improves the sound. Everything gets tighter and more focused with improved definition. However the natural softness and lower midrange body disappear which are key to the CD9. Hence I auditioned the player with the upsampler off.

We also get the option to change the DAC's output filter. The Burr Brown chip in the CD9 allows us to choose between fast/steep and slow/shallow filters. Without a shadow of a doubt the latter resulted in a more natural sound although from a technical point of view it's inferior as it generates higher distortion values.

Conclusion. Audio Research continues to do its own thing and even the change of ownership in 2008 did not disrupt this trend. The Reference CD9 is another step up on a previously chosen path. Hence we are not dealing with a revolution or breakthrough but rather a continuation and refinement. The sound is dense and warm, its center of gravity shifted towards the lower midrange. The CD9 handles digital in a special way by eliminating what's commonly associated with it: treble impurity, harshness and nervousness. The only nervousness we experience with this deck is reaching an album's end and needing to swap in another. This is more of a friend than tool. Resolution and selectivity of a dCS player for example are an order of magnitude better as is the ability to separate individual layers of an Ancient Audio or Mark Levinson deck. However the top ARC player from its Reference Series has something no other CD player I know seems to have: the freedom to reproduce any material in a way we would like to hear it over LP. There are some cons involved but the pros far outweigh them. The digital inputs, most importantly USB, are a valuable addition necessary in the 21st century. This is a machine for the ages, made to easily survive the passing of time and sounding so good that no temporary audio fads or 'inventions' should wipe the smile of satisfaction off the face of a music lover who purchased it.