Externally, Yamaha's CDX-1110U CD player is virtually identical to its direct predecessor, the equally excellent CDX-1100U, which was re viewed in the October 1987 issue and to which this magazine gave a Product of the Year award for its Hi-Bit technology.
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Dimensions: 17 1/4 by 4 3/4 inches (front), 15 3/4 inches deep plus clearance for connections. Price: $1,199. Warranty: Limited, one year parts and labor. Manufacturer: Yamaha Corp., Japan. U.S. Distributor: Yamaha Electronics Corporation, U.S.A., 6660 Orangethorpe Ave., Buena Park, Calif. 90620.
-------------The new unit has only a few changes on the front panel. First, and most trivially, the track-skip buttons have had their identifying symbols changed from a plus and a minus to the more common double arrows. The disc drawer also now carries three bits of printed-on self-advertising: "Hi-Bit Twin D/A Converter" (a fact left unstated on the 1100), "18-bit D/A Converter System" (which, strictly speaking, is true of neither the 1110 nor the 1100), and, most significantly, "8x Oversampling Digital Filter" --this last a feature new to three of Yamaha's latest CD players (the CDX-1110U, -910U, and -810U).
Yamaha's proprietary digital output filter does operate at eight times the nor mal CD sampling rate (352.8 instead of 44.1 kHz), but this too implies the wrong thing. The 1110 indeed generates seven mathematically interpolated data points between every two original samples, but the filter itself is not a brute-force eight times device. Instead, it has three separate processing stages, each correcting for the re-sampling artifacts generated by the preceding stage's processing.
The first stage of the digital filter is a 225th-order digital low-pass process operating at twice the CD sampling rate (88.2 instead of 44.1 kHz). The second stage is a 41st-order low pass filter with resampling at four times the CD sampling rate (176.4 kHz). This stage removes the ultrasonic artifacts ("images") around 88.2 kHz and 264.6 kHz that were generated by the first stage.
The last stage operates at 352.8 kHz and is a 21st-order low-pass filter designed to remove the components around 176.4 kHz created by the first two filter stages.
The resulting spectrum, as shown in the Yamaha literature, is essentially that of an eight-times resampling device, with the only remaining ultrasonic image centered around 352.8 kHz. And this energy, explains a Yamaha white paper, "is so high in frequency it virtually disappears when it is run through a normal audio buffer amplifier." What all this processing has enabled Yamaha to do is remove altogether the analog output filter used in the earlier 1100 (and in virtually every other CD player ever made). As the white paper puts it: "The benefit of eliminating the analog filter, of course, is that the intra channel phase shift (which can be quite gross even in highly regarded players) and distortion associated with such filters is virtually eliminated .... Descriptive terms such as clear, open, transparent, a well-positioned image, and good dimensional quality are often used to de scribe signal improvements associated with reductions in phase distortion." We're skeptical, however, of the assumption that any and all reductions in phase distortion are audible, even the elimination of the small audible-band phase nonlinearity introduced by the 1100's slow-rolloff filter with its -3-dB point already in the ultrasonic range. I, for one, will not believe this until I am presented with reliable evidence. And I find it ironic that after all this talk about phase response, the new 1110 applies a 180-degree phase shift to everything- i.e., it is polarity-inverting (which is neither rare nor of audible consequence). You can judge for yourself the effect of eliminating the analog filter. For in addition to a new optical digital bit stream output to accompany the pin jack digital output that is already present on the 1100, the back panel of the 1110 has two pairs of analog outputs: Direct and Filter. The Direct output is fed straight from the output of the Hi-Bit digital-to-analog converters (DACs), and its signals contain the residual low level ultrasonic noises (centered around 352.8 kHz) associated with the digital filtration and digital-to-analog conversion process. These spurious signals are visible on a magnified oscilloscope trace, but they are inaudible. The Filter output is the analog-filtered version of the Direct signal and is provided for those people who "actually may prefer the 'softer' treated sound," as Yamaha's literature puts it.
I could not hear any difference be tween the outputs, with music or test signals, but I prefer using the Filter output to prevent the residual ultrasonic garbage of the Direct output from possibly cluttering up the rest of my audio sys tem. The analog filter used is a three-pole Butterworth design with a turnover frequency of 38 kHz.
The CDX-1110U's true value is hinted at in Diversified Science Laboratories' test data (all taken from the Filter output), which indicate excellent to superb audible performance. Note especially the linearity figures, which are among the most accurate I have seen.
The only real disappointment is the relatively high calculated deviation from the player's otherwise extraordinarily flat response that occurs when the analog de-emphasis circuits are switched in for playback of discs made with treble pre emphasis. This amount of deviation would be audible if compared to another player with equal but opposite changes in de-emphasized frequency response.
(When is some company using high-resolution filtering and conversion circuitry going to do de-emphasis in the digital do main and, for once, get it exactly right?) The 1110's superior linearity performance is audible as such. It can be heard most clearly on the ultra-critical Track 20 of CBS's CD-1 test disc, probably the single most difficult-to-reproduce track in all of CD-land. This track contains a 500-Hz dithered sine wave slowly decreasing in level from -60 dB to -120 dB (yes, it is possible to hear signals below the CD dither-noise level of around -90 dB). On a player with perfect low-level linearity, that's all you will hear: a sinewave dropping into white noise. There will be no distortion of the sine wave audible above the noise level, and the noise itself will not change in perceived "whiteness" as the signal decays. In this regard, the Yamaha 1110 is equaled in my experience only by its predecessor and a few (not all) players using true 18 bit DACs. The distortion in the sine-wave is lower than in most players and the noise remains white throughout.
This performance can be attributed to Yamaha's Hi-Bit technology that pro vides not so much 18-bit performance as greatly reduced 16-bit nonlinearity at low levels.
Keep in mind that, to hear any of these effects, I had to boost the 1110's output some 60 dB by sending it through the microphone inputs of a cassette deck and turning the recording-level controls all the way up. The deck outputs were then fed to a preamp for more boosting and listened to through headphones and observed on a one-third-octave spectrum analyzer. This is hardly normal listening procedure for music. Still, it is a testament to the quality of Yamaha's D/A circuitry.
Operationally, the 1110 and its infrared remote control work absolutely identically to the earlier model. The 24-selection programmed playback, random track playback, high-speed track/index point cueing, two-speed disc scanning, and track/disc/A-B loop repeat functions remain unaltered. Also retained in the 1110 is the 1100's solid feel, which stems as much from the all-metal front panel controls as from the unit's considerable mass (more than 30 pounds). Unfortunately, the digital volume control also seems to be unaltered from the earlier model. I recommend that perfectionists keep it at full-on or use it only as a temporary muting device, because at medium to high attenuations it adds visible (on the scope) and slightly audible distortions to low-level signals, thus erasing some of the advantages of Hi-Bit conversion.
My recommendation? Forget about 18-bit filters, the degree of oversampling, and the elimination of the analog output filter. Simply listen to the CDX-1110U realizing that you won't hear a more linear-sounding CD player in even the most stringent direct comparisons, whether with music or with test signals. It may lack the glittering front-panel and splashy programming/cueing features of other CD players, but the features most people actually need are well provided for--and, sonically, Yamaha's CDX 1110U is as good as they get.
-David Ranada
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All data were obtained using the CBS CD-1. Sony YEDS- 7.
Philips 410 055-2, and Philips 410 056-2 test discs.
Except where noted otherwise, data are tor the analog filtered output
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Also see:
Cambridge Audio CD-2 Compact Disc player (review, Oct. 1988)
Vector Research VRX-5200R audio-video receiver (review, Oct. 1988)