Sidebar 3: Measurements
I measured the Cyrus CDi-XR using my Audio Precision SYS2722 system. This player doesn't have digital inputs, so I used test signals burned on a CD-R. As these signals are restricted to a word length of 16 bits, this affected my measurements of resolution and noisefloor.
I used the Pierre Verany Digital Test CD to check the CDi-XR's error correction. It played the tracks with gaps in the data spiral up to 0.5mm in length without stuttering, but there were audible glitches when the gap was 0.75mm and longer. The Compact Disc standard, the so-called Red Book, requires only that a player cope with gaps of up to 0.2mm, but the Cyrus's error correction is not as good as that of the best players or transports I have measured in recent years (footnote 1).
The CDi-XR's output impedance was a suitably low 47 ohms from 20Hz to 20kHz. A 1kHz signal at 0dBFS resulted in an output level of 2.4V, which is 0.4V/1.6dB higher than the CD Standard's recommended maximum level of 2V. The Cyrus's impulse response (fig.1) indicates that the output inverts absolute polarity and that its reconstruction filter is a conventional linear-phase type, with equal amounts of ringing before and after the single sample at 0dBFS that I created for this test.
As seen in fig.2, the Cyrus CD player featured very low levels of harmonic distortion. The third harmonic was the highest in level (fig.6), laying at just –94dB (0.002%). While higher harmonics can be seen in this graph, these were all below –110dB (0.0003%). Fig.6 was taken with the very high 100k ohm test load, but, commendably, none of the harmonics increased in level when I reduced the load to the current-hungry 600 ohms. Intermodulation distortion with a mix of equal levels of 19 and 20kHz tones was vanishingly low in level (fig.7), though the rise in the noisefloor centered on 10kHz that was present in fig.2 is also evident in this graph.
I tested the CDi-XR's rejection of word-clock jitter with the undithered Miller-Dunn J-Test signal (a high-level tone at one-quarter the sample rate over which is overlaid the least-significant bit toggled on and off at a frequency equivalent to the sample rate divided by 192). The Cyrus reproduced the odd-order harmonics of the LSB-level, low-frequency squarewave very close to the correct levels (fig.8, sloping green line), and no other sidebands were present. However, fig.8 also shows the rise in the high-frequency noisefloor that was also present in figs.2 and 7.
Footnote 1: See, for example, my measurements of an ATC CD player.
Fig.1 Cyrus CDi-XR, impulse response (one sample at 0dBFS, 44.1kHz sampling, 4ms time window).
With white noise at –4dBFS (fig.2, red and magenta traces), the CDi-XR's response was flat in the audioband but rolled off sharply above 20kHz, reaching full stop-band suppression at the Nyquist frequency of 22.05kHz (green vertical line). An aliased image at 25kHz of a full-scale tone at 19.1kHz (blue and cyan traces) lies at just –101dB (0.0009%), but a higher-level image (–83dB) is present at 69.1kHz. The distortion harmonics of the 19.1kHz tone all lie below –100dB (0.001%), though a small rise in the noisefloor with this signal can be seen both in the audioband and between 45kHz and 55kHz.
Fig.2 Cyrus CDi-XR, wideband spectrum of white noise at –4dBFS (left channel red, right magenta) and 19.1kHz tone at 0dBFS (left blue, right cyan), with data sampled at 44.1kHz (20dB/vertical div.).
Channel separation (not shown) was good at 79dB in both directions from 20Hz to 20kHz. The low-frequency noisefloor was clean (fig.3), with power supply–related spuriae all lying close to –120dB. The random noise components in this graph are due to the dither used to encode the full-scale 1kHz tone. Similarly, the noisefloor in a spectrum taken with a dithered tone at –90dBFS (fig.4, cyan and magenta traces) is due to the dither. Repeating spectral analysis with "digital black" (blue and red traces) indicates that the CDi-XR's noisefloor is 20dB lower than that of dithered 16-bit data. With undithered 16-bit data representing a tone at exactly –90.31dBFS (fig.5), the three DC voltage levels described by the data were well resolved, and the waveform was perfectly symmetrical. An inconsequential 25µV positive DC offset is present in the right channel (red trace).
Fig.3 Cyrus CDi-XR, spectrum of 1kHz sinewave, DC–1kHz, at 0dBFS (left channel blue, right red; linear frequency scale).
Fig.4 Cyrus CDi-XR, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with 16-bit data (left channel cyan, right magenta) and with "digital black" (left blue, right red) (20dB/vertical div.).
Fig.5 Cyrus CDi-XR, waveform of undithered 16-bit, 1kHz sinewave at –90.31dBFS (left channel blue, right red).
Fig.6 Cyrus CDi-XR, spectrum of 50Hz sinewave at 0dBFS, DC–1kHz, into 100k ohms (left channel blue, right red; linear frequency scale).
Fig.7 Cyrus CDi-XR, HF intermodulation spectrum (DC–30kHz), 19+20kHz at 0dBFS into 100k ohms (left channel blue, right red; linear frequency scale).
Fig.8 Cyrus CDi-XR, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 16-bit CD data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.
As the Cyrus CDi-XR has digital outputs, to allow it to be used as a CD transport with a separate D/A processor, I examined the quality of those outputs. Fig.9 was taken from the TosLink output with J-Test data plotted over one "unit cycle." The eye pattern is wide open, with almost no blurring of the leading and trailing edges. The average jitter level, assessed with a 50Hz–100kHz bandwidth, was relatively high, at 2286 picoseconds (ps) compared with 340.5ps when I looped the Audio Precision SYS2722's TosLink output to its optical input. The jitter present in the CDi-XR's optical output will be inconsequential when the Cyrus is used with a D/A processor that has good jitter rejection, but the coaxial S/PDIF output, which offered a jitter level of 583.7ps, is to be preferred.
Fig.9 Cyrus CDi-XR, eye pattern of TosLink data output carrying 16-bit, 44.1kHz J-Test data (±2.5V vertical scale, 175ns horizontal scale).
The Cyrus CDi-XR offers generally good measured performance, although I do wish it had digital inputs. I suspect that its intrinsic performance is limited by the 16-bit CD medium.—John Atkinson
Footnote 1: See, for example, my measurements of an ATC CD player.
