Mark Levinson No.360 D/A converter Measurements part 3

Distortion levels were negligible. Spectral analysis of the No.360's output while it decoded data representing a 50Hz sinewave at 0dBFS (fig.7) revealed traces of second and third harmonic, but at almost 100dB down from full-scale these will be benign. This graph was taken from the balanced output; from the single-ended output, the third harmonic stayed where it was but the second harmonic rose to a still-negligible -94dB (0.005%). The Levinson's performance was equally good on the punishing full-level high-frequency intermodulation test. The 1kHz difference tone was almost 90dB down from the unbalanced outputs (fig.8), dropping to -94dB from the XLRs.

Fig.7 Mark Levinson No.360, balanced spectrum, DC-1kHz, 50Hz at 0dBFS, 100k ohm load (linear frequency scale, 20dB/vertical div.).

Fig.8 Mark Levinson No.360, unbalanced HF intermodulation spectrum, DC-22kHz, 19+20kHz at 0dBFS, 100k ohm load (linear frequency scale, 20dB/vertical div.).

Finally, the No.360's sophisticated input circuitry does indeed do an excellent job of recovering the data with a minimum amount of word-clock jitter. Using the Miller Audio Research analyzer on the left-channel unbalanced output with the processor driven by our standard PS Audio Lambda transport via an ST-optical link gave me the spectrum shown in fig.9. (The grayed-out trace in this graph is a spectral analysis of the mbl 1611HR's output taken under identical conditions.) The absolute level of the jitter content was a low 157 picoseconds (compared with the Mark Levinson flagship No.30.6's 153ps), with the low-order data-related components (red numbered sidebands) much lower than with the German mbl processor. Some very low-frequency components were present, including a pair of supply-related sidebands at ±60Hz (green "1" markers), but these were almost buried in the noise floor. The only other sidebands of particular interest lay at ±386Hz (purple "4" markers), but I have no idea what these are due to.

Fig.9 Mark Levinson No.360, high-resolution jitter spectrum of 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 mbl 1611HR.

Overall, this is excellent measured performance, with no areas of weakness.—John Atkinson

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