Also, I am re-evaluating some early scores in reviews that reflect measured performance. The emergence of superior evaluation technology and software skills require some rating changes, to be fair and consistent. Apologies for this, however I feel it is the best way forward for our fledgling publication, as we grow our identity and solidify our standards.
Ahhhh. There is nothing more satisfying than fixing, or rather, bypassing a bug in the system. You may have noted the issue in the white noise filter frequency response graphs. Something about the internal tone generator in the ARTA software creates a 'hiccup' at the Nyquist limit. It does not affect the accuracy of the measurements, at least those 'outside' the hiccup. It is almost as if the white noise started imaging above the original sample rate Nyquist limit as one looks at the oversampled filter plot. The filter quickly brings things back to normal, but that little anomaly shouldn't be there. There should be a smoothly rolling off plot.
Bypassing the ARTA internal tone generator with external tones fixed the issue. Along with fixing that issue, I changed the color patterns quite drastically, which, in my opinion, is much more pleasing to see. The white background with red and blue data plots simply looks better than the default green over black. At least here at Euphonic Review. Opinions vary of course.
See below the results. The GTO filter finally looks like it should. It resembles the MQA filter. No surprise since iFi collaborated with Meridian on this filter. It is personally my filter of choice, and Thorsten Loesch (when he was still actively the iFi engineer) explains it well in the tech notes, which you can access here by clicking. (GTO FILTER PDF)
Below are the iFi NEO DAC fw 3.33 filter profiles. Once again, the only anomaly here is the filter called 'Minimum'. One would likely interpret that as meaning 'Minimum Phase'. It is not a Minimum Phase filter, however. The measurements show it to be a low tap, short linear phase filter.
I hope you like the new filter graph format. Without any further delay, here are what the iFi NEO DAC 3.33 firmware filters look like.