If you need a small and very portable DAC with a good sound quality Ifi devices are a good choice (ADI-2 PRO/DAC are superior by far, but different user scenarios).

All the other gadgets ifi offers are the typical HighEnd marketing hype which makes this so annoying for many customers. The power supplies could have an impact with the portable ifi DACs for stationary use. But my experience is that battery power produced the best sound quality with ifi DACs. Absolutely no improvement with RME devices.

I can not support the argument that all other reviewers would have been idiots.
If they have not tested accessories or did not know about a specific one they have no experience or test results.

Some accessories make sense even if a reviewer or many reviewers did not mention it.

But these USB purifiers/filters/conditoners are nonsense, at least with modern and well designed DACs like the RME devices.

Oh, I got your point, just read my post. Though, I used a less colorful language and opened another perspective. Not everything is black and white.

An improvement in sound quality does not mean it was bad before. It also could be a matter of taste. Our perception is never objective it is always subjective.

Not all so called High-End (audiophile) equipment is nonsense. But it can be very hard to separate the "real gear" from marketing hyped nonsense. Because of this difficulty some users ignore it and condemn everything/everyone (Ignorance is bliss), it is so much easier, and others just jump on that train, without being critical and thinking their perception is always right.

I test new equipment or accessories for many, many hours, sometimes for weeks to eliminate subjective perception issues as good as possible. That is very time-consuming and can be very exhausting. But that is the way to go if you want to offer the best solution to your customers.

Edit: corrected some typos

@bejoro

Are you sure we are talking about the same device? DC iPurifier, not USB iPurifier? It's totally different stuff

@ramses

I wouldn't believe in SUCH a difference, of course. I take it as a semantic hyperbole: the reviewer heard a change of sound and liked it, that's all.

I know ADI-2 DAC work well with its own power supply. My question is: does it mean there is no space for improvements? In this case, we don't talk about theoretical possibilities - the reviewer connected iFi device to ADI-2 DAC, not to "some DAC". And he noticed something. Described effect surprised me a bit, but - even when I take it with a grain of salt - I wouldn't say it's impossible at all.

So, I repeat my question:
Do you have any EXPERIENCE with iFi DC iPurifier connected to the ADI-2 DAC?

Neither the DC iPurifier nor the USB iPurifier makes any difference, both tested with different (modern, well designed) DACs, also with ADI-2 PRO FS.

There is no way such a device can improve sound quality (picture, remove a veil, sound stage or other idiophool’s BS.
It may suppress a hum or a buzz for example, but that’s all.
Please consider how USB works. It’s physics, not magic.

I did not suggest that there must only be subtle or very small differences to be evaluated thoroughly. It is necessary to evaluate even strong differences thoroughly whether they are an improvement or a degradation in sound quality no matter how tempting they may seem on a first impression (subjective nature of perception can lead to a wrong conclusion).

Sounds as if you want to launch another discussion about psychoacoustic effects.

I am pretty sure that you also believe into audiophile usb cables...

Sorry but the claims of this product and the recommended mercury usb cable for €300 are pure nonsense.

The data transfer up to the dac's d/a converter is pure digital and even jitter is not relevant as steadyclock will eliminate any jitter. The d/a conversion inside the adi-2 dax/pro is being performed by the interface femtosecond clock.

So the digital transfer of data and d/a conversion are decoupled from each other.

As long as there are no transmission error's over USB because of a bad or too long  cable or cheap connectors, soldering points, etc Any cheap cable will do.

You only fool yourself (and potentially others).

Thanks was missing this link.

I'm not interested in what ifi says about recommended usb cables.
I think there is a difference that I have done the test while you are not. And I do not claim to have goldenears or platinum pockets ... And I do not think I bother anyone in the way I expose my views. Unfortunately it is not easy to upload a picture from the test done a few months ago.

Just bought ADI-2 DAC and appreciate engineering level of the product! Thank you, guys from RME for your effort!

Still I cannot understand why we need so straightforward (I would say primitive) explanation of digital gear like this:
"here is NO way any gradual difference in data transmission could have a specific, reproducible, and recognizable effect on the audio signal ("stereo width", "stage", "spaciousness/localization", or whatever other voodoo criteria".

All above mentioned criteria are not "voodoo" at all.
We are not talking about "specific, reproducible, and recognizable effect" leads to a saxophone sounds like a piano on all records, right?
Instead, life-like "stereo width", "stage", "spaciousness/localization" are all mandatory attributes of high resolution system.
Take first generation CD-player (12 bits of real resolution) and 20 bucks headphones - and you get just "stereo" but no "stage" or "spaciousness/localization"".

I spent quite long time playing with classical highest-grade multibit DACs like AD1862 and others many years ago. These DACs classical implementation had some potentiometers for linearity (=resolution) adjustment. Turn it incorrect (the DAC becomes more like 12-14 bit resolution) - and no "stage" or "spaciousness/localization" is here. Turn it precise and accurate (linearity at least 16 or more, close to 18 bits) - and you'll get all these "voodoo".

How is it possible to affect linearity\resolution otherwise then by "turning potentiometers"? It is more than easy! Just get low-quality power supply with high leakage current, get cheapest poor shielded digital cables which will radiate EMI to sensitive analog circuits, etc. etc. - and you are done!
No magic, no woodoo at all.
Just straightforward physics.

@maartenl, are you ok, man?

Where have you found anything related to snake-oil in my post?
I'm worrying about you.

Truly yours,
dukua,
engineer since 1994,
silicon valley.