Wadia 27ix & Wadia 270 transport Measurements part 2

Wadia's DigiMaster filter gives a very good squarewave shape (fig.3), with just a single overshoot cycle. The overshoot is preserved when the sample rate is doubling to 96kHz (fig.4), but its period is halved. And while a 96kHz-sampled, 12kHz squarewave is not particularly square (fig.5), it does have a very good fundamental-plus-third-harmonic shape.

Fig.4 Wadia 27ix, 1kHz squarewave at 0dBFS, 96kHz sampling.

Fig.5 Wadia 27ix, 12kHz squarewave at 0dBFS, 96kHz sampling.

The Wadia 27ix injects extremely low levels of noise into its analog output. Fig.6 shows the spectrum of a dithered 1kHz tone at -90dBFS, with the data word length set to 16 bits (top) and 24 bits (bottom). Other than a glitch at 2kHz, which experience suggests is inherent to the Audio Precision, the traces are free from spuriae. You can see that the right channel is indeed noisier than the left below 700Hz, with about a 6-7dB difference in the 24-bit case. Above 2kHz, the increase in word length results in a drop of the noise floor of 12dB or so, implying better than 18-bit performance, which is excellent. (The volume control was set to its maximum for this measurement.) A similar improvement is seen in fig.7, which shows a wideband spectral analysis of the Wadia's output while it decodes data representing digital silence with 16- and 24-bit word lengths.

Fig.6 Wadia 27ix, balanced outputs, spectrum of dithered 1kHz tone at -90.31dBFS, with noise and spuriae: 16-bit data, top; 24-bit data, bottom. (1/3-octave analysis, right channel dashed.)

Fig.7 Wadia 27ix, balanced outputs, spectrum of digital silence with noise and spuriae: 16-bit data, top; 24-bit data, bottom. (1/3-octave analysis, right channel dashed.)

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