i have looked at stereophile measurements a couple of times are they as accurate as amirms?
Here is what it says about the dac i use daily in my system
Channel separation (not shown) was excellent, at 125dB in the midband and still 115dB at 20kHz, and the Music Streamer HD was very quiet.
The top two traces in fig.3 were taken by sweeping a 1/3-octave bandpass filter from 20kHz down to 20Hz while the Music Streamer HD decoded 16-bit data representing a dithered 1kHz tone at –90dBFS. The traces peak at exactly –90dBFS, suggesting minimal linearity error, which was confirmed by additional testing (not shown).
With 24-bit data (fig.3, middle traces), the noise floor drops by up to 24dB, suggesting that the DAC has around 20-bit resolution
With its superb resolution and low noise, the Music Streamer HD's reproduction of an undithered 16-bit tone at exactly –90.31dBFS was perfect (fig.5): the waveform is superbly symmetrical about the time axis, the three DC voltage levels described by the data are readily resolved, and the Gibbs Phenomenon "ringing" on the tops and bottoms of the waveform is not obscured by noise. This ringing also indicates that the HRT's reconstruction filter is a conventional linear-phase type. With undithered 24-bit data, the result is an excellent sinewave (fig.6).
At low frequencies (fig.7), the distortion signature comprises a collection of harmonics that decrease with order, with the second harmonic the highest in level, at –100dB (0.001%). The picture changes at higher frequencies, however, with the third harmonic now the highest in level (fig.8), at –90dB (0.003%). And looking back at fig.2, the third harmonics of the 19.1kHz tone in that graph lie at –66dB (0.05%). So though the distortion is low at all frequencies—and, commendably, unaffected by reducing the loading to 600 ohms!—there appears to be a relationship between the distortion spectrum and the signal frequency. I have no idea if this will have any bearing on the HRT's sound quality.
An asynchronous USB connection should be free from jitter problems; the Music Streamer HD's reproduction of 16-bit/44.1kHz J-Test data is excellent (fig.10), there being no jitter-related sidebands visible around the 11.025kHz tone, and all the odd-order harmonics of the 229.6875Hz LSB-level squarewave lie at the correct levels. With 24-bit J-Test data there appeared a pair of sidebands of unknown origin, at ±150Hz and a level of –135dBFS (fig.11).
Overall, HRT's Music Streamer HD measures significantly better than the Music Streamer Pro. There is, however, still that peculiar behavior with high-level 19 and 20kHz tones to contend with
What do they mean by that? high level tones?
