Classé Omega Super Audio CD player Measurements part 3
Fig.9 Classé Omega, balanced spectrum of 50Hz sinewave, DC-1kHz, at 0dBFS into 100k ohms (linear frequency scale).
Thankfully, things don't get significantly worse into the punishing 600 ohm load (fig.10), though the fifth harmonic rises by 12dB. Working against the audibility of this behavior is the low order of the distortion harmonics. The levels of intermodulation distortion products are also low, even into 600 ohms (fig.11). But I still would like to have seen better performance on these tests.
Fig.10 Classé Omega, balanced spectrum of 50Hz sinewave, DC-1kHz, at 0dBFS into 600 ohms (linear frequency scale).
Fig.11 Classé Omega, balanced HF intermodulation spectrum, DC-24kHz, 19+20kHz at 0dBFS into 600 ohms (linear frequency scale).
Finally, I assessed the Omega's jitter performance using the Miller Audio Research Analyzer. This program, based on a National Instruments PC card, works in conjunction with a diagnostic signal stored on a CD-R with low timebase error. The software performs a high-resolution spectral analysis of the player's analog output with the special signal, then searches the FFT "bins" for symmetrical sideband pairs, which will in the main be due to word-clock jitter.
The result for the Classé Omega's single-ended output—the NI card only has a single-ended input—is shown in fig.12. Data-related jitter—the sidebands indicated with red numeric markers—is very low, at a calculated 172.4 picoseconds peak-peak. But a largish number of noise spikes can also be seen (light blue numeric markers), with the highest in level, at 9.6kHz, ringed in red. This noise, as well as a random noise floor some 6-7dB higher than the best I have measured with this test, reduces the Classé's dynamic range.
Fig.12 Classé Omega, high-resolution jitter spectrum of unbalanced analog output signal (11.025kHz at -6dBFS with LSB toggled at 229Hz). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz. Grayed-out trace is similar analysis for 11.025kHz tone (no LF LSB toggling) from SACD.
The grayed-out trace just visible in this graph is a similar spectral analysis performed with the Omega playing an 11.025kHz tone from the Sony test SACD. The random noise components are very slightly higher in level, though the noise spikes are both fewer in number and lower in level.
The Classé Omega's generally good measured performance was let down by the poor channel separation from the unbalanced outputs, the highish distortion from the balanced outputs, its inability to lock reliably on to external datastreams with high sample rates, and the compromised dynamic range compared with the best CD and SACD players I have measured. However, this last point is almost certainly connected with the player's use of a passive I/V converter topology, which can certainly sound superb.—John Atkinson