Laboratory test report
The output voltage of the Lumin D1 varies depending on which option you use in its App settings. If you choose the XLR output and go with the default ‘normal’ output level, the Lumin D1 delivers 4.0347 volts to the left channel output and 4.0431 volts to the right channel output, which means that channel balance is an excellent 0.018dB. The same ‘normal’ setting delivers exactly half that output voltage to the unbalanced RCA terminals. (That is, 2.017 volts to the left channel and 2.021 volts to the right.)
Choosing the ‘low’ output level will mean that the Lumin D1 delivers around 2.4 volts to the XLR terminals and 1.2 volts to the RCA terminals. All of Newport Test Labs’ tests of the Lumin D1’s performance were made using the XLR terminals and the ‘normal’ output setting, and all were made using CD-standard 44.1kHz, 16-bit digital test signals in WAV format.
The frequency response of the Lumin D1 was ruler-flat up to 1kHz, after which it rose slightly to the 22.05kHz cut-off dictated by the test signal, so that at 22.05kHz it was 0.08dB high, giving a normalised frequency response of 20Hz to 22.05kHz ±0.04dB, which is excellent. This response is shown in Graph 9. Note the vertical scaling makes the hf ‘rise’ visually larger than it would be with more conventional graph scaling.
Channel separation (not graphed, but shown in the tabulated results) was outstandingly good, with a best result of 139dB at 1kHz, only slightly less (138dB) at 20kHz, and still a truly excellent 120dB at 16Hz. Channel phase errors at these same frequencies were also exceptionally low, at +0.01°, –0.05°, and –0.92° respectively. Group delay was typical of an oversampling delta-sigma DAC at 180° (1–20kHz) and 5.4° (20–1kHz).
Also outstanding was the Lumin D1’s signal-to
noise ratio, which was measured by Newport Test Labs as being 109dB unweighted, improving to 119dB with standard A-weighting.
De-emphasis was very slightly off-target, with an error averaging about 0.3dB at the three test frequencies, but the error is slight.
As usual, Newport Test Labs measured distortion at a variety of recorded levels. At maximum output (Graph 1) you can see that
all distortion from the Lumin D1 was more than 100dB down, with a second harmonic at –122dB (0.00007%), a third at –100dB (0.001%), a fifth at –104dB (0.00063%), a sixth at –135dB (0.000017%), a seventh at –109dB (0.00035%) and a ninth at –119dB (0.00011%). All these levels are far too low to be audible, but from Graph 2, which shows distortion at –10dB, it would appear that they were due to slight overload in the analogue output stage, because at the lower level only two harmonic distortion components are visible, a second at –108dB (0.00039%) and a third at –127dB (0.00004%).
At a recorded level of –20dB, only a single third harmonic component was visible above the noise floor, at –126dB (0.00005%) and, as you can see, the noise floor across the audio spectrum is right down at –140dB, so the 119dB signal-to-noise figure would seem to indicate that most of the noise is outside the audio band where it would not be audible. At a recorded level of –91.24dB, with an undithered test signal, the Lumin D1 exhibited excellent performance, with noise dropping below the –140dB limit of Newport Test Labs’ spectrum analyser. There are odd harmonic
distortion components, and some LSB artefacts evident, but overall, it’s an excellent result. Adding dither (as would be the case with all music CDs, as distinct from test CDs) immediately removed both the distortion components and the artefacts, with the only penalty being an increase in the level of the Lumin D1’s noise floor, but since it ‘increases’ to only –140dB, this is of no concern whatsoever.
The overall THD+N figure measured by Newport Test Labs is tabulated, as you can see, and comes in at just 0.0018%: self-evidently an excellent result. Linearity error was also very, very low, with absolutely no error at all at –60dB and a ‘worst-case’ error of only 0.12dB (at –89.46dB).
Intermodulation distortion was very low for both SMPTE and CCIF measurements. The SMPTE measurement (Graph 6) shows some unwanted activity up around 14kHz, which is a product of the second harmonic of the higher of the two test signals (at 7kHz) intermodulating with the lower signal (at 60Hz). You can also see sidebands clustered around the 60Hz and 7kHz test signals. However, since all these are more than 115dB down (0.00017%), they’re insignificant. CCIF IMD is even lower again, as you can see from Graph 7.
The quality of the digital signal at the Lumin D1’s digital output is very, very good, so if you did want to use it to drive an external DAC you can be assured of feeding it a stateof-the-art digital signal, but the D1’s internal conversion is of such a high standard that I can’t see why you’d bother. You can see Newport Test Labs’ results in the ‘Digital Section’ of the tabulated results.
The impulse and square wave oscillograms captured by Newport Test Labs show that Lumin is using standard oversampled delta-sigma digital-to-analogue conversion, with the time-reversed ringing that results clearly evident on both waveforms, and indeed this proved to be the case, with Lumin using twin Wolfson WM8741s: one for each channel.
Lumin’s D1 Network Music Player returned outstanding results in all the tests performed by Newport Test Labs. Stephen Holding