Although the title might evoke images of the Matrix films and its blend of Eastern religious esotericism with gnostic undertones, this is far more simple than that. Thank God. (or should that be Brahma? anyway.....)
After measuring the iFi iDSD NEO v1.1 (original version that came to market), I decided to turn back and re-measure the ZEN DAC V2, which I keep around as a baseline for evaluating all DAC/headamps under $1000. Yes, it sounds that good. Since my original measurements of the ZEN, I have upgraded my lab considerably, and can see deeper and more accurately into what is happening in these hyper sensitive pieces of kit.
What I found was very interesting, although it should have come with no surprises, as already once in this post I have mentioned the veracity of the ZEN V2, and how it punches well above its weight class. The ZEN and the NEO measurements are for all intents and purposes identical.
The only major difference I can see, if it is major, is the falloff of the harmonic distortion is a bit smoother in the NEO. Both, however, produce more even order distortion than odd.
It comes as little surprise then that I think both sound identical. Perhaps one does a certain passage of music better than the other, then the tables are turned when the passage is of a different constitution.
Here for your viewing is the 1khz distortion FFT for each.
As I had mentioned in a previous blog entry, iFi released a version of the NEO iDSD called the 'Performance Edition'. The reality of this release is it is the same hardware as the first NEO iDSD to hit market at end of 2020. The differences are a newer firmware and a couple hardware add-ons.
Eventually iFi released the 3.33 firmware to all NEO iDSD owners. The major feature added by this upgrade is a choice of digital filters, similar to the Gryphon. (they are both xDSD platform based, and much of this also overlaps with the work done a few years earlier with the iDSD Pro.
I caught a small bug in the firmware right off the top. When GTO filter is selected, the info readout shows 'DXD 352' when, for example playing back 44.1khz and its multiples. The other filters simply show the actual sample rate. There is nothing wrong here, just a peculiar anomaly. I suspect that every filter option except for GTO are the onboard Burr-Brown chip filters. (the Bit Perfect setting is not really a filter.. there is no oversampling) The GTO filter, however, is part of the FPGA/XMOS digital processing, and behaves just like it does on the iDSD PRO. When playing anything other than Bit Perfect mode on the iDSD Pro, the display shows the oversampled rate, which is always DXD x2 (705.6khz or 768khz). Coming back around to the NEO iDSD, the small bug is once GTO is selected, the indicator display will always show the oversampled rate rather than the input rate, regardless of which filter is selected. It isn't a big deal when you understand what is going on. Everything is functioning properly, but can understandably be confusing.
Hi-Fi News review of the Gryphon pointed out several of the filters were misidentified, and that the minimum phase filter was not a minimum phase filter at all.
I have confirmed in my testing of the 3.33 firmware that all filters EXCEPT minimum phase are true to their name. As Hi-Fi News uncovered with the Gryphon, the Minimum Phase filter on the NEO iDSD is actually a short linear phase filter, the standard filter only being slightly longer.
The impulse response for each filter is below.
As far as overall performance differences? Yes, there were some measurements that showed the fw3.33 version to be slightly more jitter prone, but the results were not repeatable and are of no great a significance to change anything.
Tests are from 3.18 firmware. Next set of testing will be done with the latest firmware installed, which will add several additional filters.
Somewhere here down in the Southern USA where the Euphonic Review lab stands, where my hobby (and primary career) is tickling the ivories, well, these days more like stomping out some Rockabilly Jerry Lee style (Rest in Peace dear Friend), I have been chasing a mystery only audiophile nerds care to chase down.
Turns out I was not the only one.. wow!!! What a consternation was stirred up online regarding the iFi NEO iDSD, a new Performance edition, and various firmware updates.
First, came the admission there is no difference in the original NEO iDSD hardware released in late 2020, and the hardware in the 'new' Performance edition. The differences in hardware consisted only of two add on accessories.. a USB iPurifier3, and a SPDIF iPurifier2. Turns out I already own the USB iPurifier. It is a solid little add on, and I found it to offer subjective improvements with certain USB DACs. The SPDIF version, unreviewed by me personally, I expect it to be and have read it be an excellent product, especially when it comes to eliminating SPDIF jitter, as it is galvanically isolated, and creates a pure, clean SPDIF signal for the receiver PLL, buffers and clocks, making their job with recovering a clean clock much easier.
Of course, this didn't necessarily sit well with many people, that may have bought a Performance version expecting more for their money. And that is understandable. Things were not helped by a chart outlining the new 'upgrades' from the original version. These were later dismissed as, put into my own words, accidental misprints and miscommunication.
I don't mind just a little speculation here at ER, and part of me wonders if part of this goes back to something the keen eye may have observed at the time; that the first release of the NEO to the public was version '1.1'. Perhaps there was one that came before that never made it to production and was quickly upgraded? Possibly. Again, I am just speculating.
I find all the more curious myself though, is the insistence that the NEO iDSD PCM oversampling filter was locked with no other choice, and this filter locked in by firmware was the in-house developed (along with help from MQA) 'GTO' filter. The GTO filter is a short (32 tap) minimum phase FIR filter that you can read all about by clicking here.
But the first major reviews with measurements showed that the filter on offer with the NEO iDSD was not the GTO filter. It isn't even minimum phase. HiFi News caught this but didn't challenge, seeming to assume their measured results were how it was supposed to behave. What they had measured was a moderately long linear phase filter with its expected stopband behavior. Now, there have been many firmware updates, so it seems, in the life cycle of this product, so things could have changed. My particular example of the hardware is version 1.1, with firmware 3.18. And just like HiFi News, my example has a slightly long linear phase FIR filter, with fairly strong stopband rejection. Definitely NOT the advertised GTO filter.
To further muddy the waters, there seems to be multiple past firmware updates, that even allow the end user to choose the single, default filter in their NEO iDSD. PLUS, there is a firmware update NEWER than my version that opens up a host of iFi filter options, ala the Gryphon or iDSD Pro.
I like iFi products. But I also like being a fair reviewer to all sides involved. So to be fair, this was a confusing mess that made a night of scrolling through the wailing and gnashing of teeth on Head-Fi time I wish I had back.
I have already finished most of my benchmarking on the NEO iDSD with the 3.18 firmware. Now, I am off to upgrade to the latest and see what I can find... hopefully what I expect to find.. no trouble down here in the southland.
Y'all come back now, ya hear? Please?
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