Sony CDP-X555ES CD player Measurements

Sidebar 3: Measurements

The Sony joined the Denon DCD-2560 and the JVC XL-Z1050 as one of the three best test-bench performers reviewed in this issue. Its frequency response (fig.1) is practically a straight line, as is its de-emphasis curve (fig.2). The Sony's 0dB squarewave response (fig.3) is similar to the others, with a bit more discernible clipping of the ripple typical of its linear-phase filter. (This clipping is merely due to a conscious design choice concerning operation of the filter.) The crosstalk graph (fig.4) requires no comment.


Fig.1 Sony CDP-X555ES, frequency response at 0dBFS (right channel dashed, 0.5dB/vertical div.).


Fig.2 Sony CDP-X555ES, de-emphasis error (right channel dashed, 0.5dB/vertical div.).


Fig.3 Sony CDP-X555ES, waveform of 1kHz squarewave at 0dBFS (2ms time window).


Fig.4 Sony CDP-X555ES, channel separation (10dB/vertical div.).

The spectrum of the Sony's response to a –90.31dB, 1kHz dithered signal (fig.5) shows a good linearity at the –90.31dB point and a small but largely irrelevant trace of power-supply noise at the 60Hz fundamental plus harmonics. The full low-level linearity test (fig.6, left channel only shown; the right was only marginally different) indicates a response which remains within 0.5dB of perfect linearity to below –100dB. Listening to the fade-to-noise with dither track produced a clean fade to the noise floor with no artifacts. And the noise spectrum in fig.7 shows the rising ultrasonic noise typical of noise-shaped 1-bit machines with no idling tones present.


Fig.5 Sony CDP-X555ES, spectrum of dithered 1kHz tone at -90dBFS, with noise and spuriae (right channel dashed).


Fig.6 Sony CDP-X555ES, left-channel departure from linearity (2dB/vertical div.).


Fig.7 Sony CDP-X555ES, Sony CDP-X555ES, spectrum of digital black with noise and spuriae (1/3-octave analysis, right channel dashed).

In fig.8, the waveform of a 1kHz, –90.31dB undithered signal indicates a good stairstep response (as it should) overlaid by a degree of noise typical of the better machines in this price category. And in fig.9, the intermodulation in response to a 19+20kHz, 0dB signal, shows a low level of distortion products. The cursor shows the 21kHz second-order product to lie a hair above –70dB with respect to the 19kHz level.


Fig.8 Sony CDP-X555ES, waveform of undithered 1kHz sinewave at -90.31dBFS.


Fig.9 Sony CDP-X555ES, HF intermodulation spectrum, DC-30kHz, 19+20kHz at 0dBFS, 100k ohm load (linear frequency scale, 10dB/vertical div.).

The Sony had a non-inverting output, with zero DC offset from either channel. Its output in response to a 0dB, 1kHz test disc signal was significantly higher than the standard 2V at 2.44V (left channel) and 2.42V (right). If not compensated for in an A/B comparison, this 1.7dB difference will make the Sony sound more dynamic, more exciting.

Finally, the X555ES's output impedance measured 197 and 199 ohms (left and right channels, respectively) from its fixed outputs, and 198 ohms from its variable output (left channel) set to full volume. At a 12:00 setting, however, the output impedance of the variable output (left channel) rose to 2407 ohms. Care should be exercised when using the Sony's variable outputs. The Sony might be expected to show erratic performance quality when used from these outputs with long cables, cables with high capacitance, a low input impedance in the next stage in the system (either preamp or power amp), or combinations of the three.—Thomas J. Norton

Sony Electronics, Inc.
16530 Via Esprillo
San Diego, CA 92127-1708
(858) 942-2400