iFi Audio iUSBPower & Kingrex uCraft (Y) Cable | Water for Your Espresso

Once in a while, curiosity will take over the logic circuits of every audio enthusiast. The audiophile will set aside common sense and proceed to justify bouts of practical insanity with the dubiously noble task of chasing audio perfection. The following article does very much the same thing — you’ve been forewarned.

Part 1 discusses the AMR iFi Audio iUSBPower, while Part 2 goes into more depth about the KINGREX uCraft (Y) USB Cable.

Part 1: iFi Audio iUSBPower (by Abbingdon Music Research)

Perhaps it was all the coffee I’d been drinking, and all the nonsense that comes with the art of making the perfect espresso. I was dissatisfied — dissatisfied with the hiss in my DAC, dissatisfied with the resolution I was getting out of the unit, and just plain dissatisfied.

My iBasso D7 was actually a very good performer for its price; at $179, it sported more features than most DACs could ever hope for, and provided enough resolution to mollify the detail monger in me. It was, however, lacking one thing — its own power supply.

You see, the D7 is an USB-tethered device, meaning that it draws its 500 mA of current straight from the power rails of a computer’s USB port. I’m no gamer, so I don’t have a desktop rig with an overbuilt 1500W power supply and its own isolated power rails. I use a plain ol’ laptop, and notebook computers are notorious for running dirty power through themselves.

Think of the difference between an $8000 espresso machine and an Aeropress: if you use the Aeropress, you’re bound to get some stray coffee grinds inside your brew, and even though the taste might be nice, it’s no match for a perfect, 9 bar, pumped espresso.

Every single time my hard disk spooled up, I heard the power spiking through my DAC. What I needed was a good USB power supply. Just like how coffee tastes better with a better-filtered source of water, I thought my DAC would surely stay more composed with a consistent and clean 5V power supply.

I knew there were USB power products out there; Audiophileo manufactures a unit praised by many — the PurePower. With a nifty status display, overbuilt enclosure, and a near-$500 price tag, the Audiophileo represented both the good and the bad of audiophile culture.

Then, along came iFi Audio. Abbingdon Music Research (AMR) is a long-standing, venerable hi-fi brand from the UK, with a foothold in the home stereo segment of audio. However, the rapid evolution of music listening from a static living room to any personal and portable space prompted AMR to create the iFi Audio sub-brand of digital and computer-oriented products. The iUSBPower evolved from this endeavor.

So why did AMR decide to embark on such an effort? Well, higher sales volumes of the lower end iFi Audio probably allow AMR to cut costs overall, even on their high-end systems, simply because of increased order quantities for shared parts. Therefore, the appearance of iFi Audio is almost certainly a win-win for both the company and consumer. We get trickle-down technology at reasonable prices, and they get to sell more gear.

With iFi Audio‘s consumer slant also comes a dedicated sales and marketing team with mighty quick response times. Working with Vincent Luke has been huge pleasure, and his support afforded me the time and space to really take a comprehensive look at the iUSBPower, both inside and out.


The iUSBPower is best described as an intricate power conditioner. iFi includes a high-quality wall wart with every iUSBPower unit that they call the “Ultra Low-Noise AC/DC Power Adapter” (yes, they’re big on the buzzwords), which provides the initial 5V power; the power supplied by USB via the computer is filtered away and replaced with clean power treated by the device.

Outwardly, the iUSBPower follows minimalism. Each of iFi Audio’s ‘Micro’ series of products, which includes a bevy of DACs, solid state and tube amplifiers, a phono stage and more, is encased in a simple, oblong aluminum enclosure. While others may disagree, I find the minimalism quite elegant — dirty USB goes in on one end, and clean USB comes out the other.


I found it cute that iFi Audio actually took the time to label which sections of the PCB board were responsible for what aspects of the power regulation. I guess they assumed that many people (like me) would be curious enough to pull the PCB out from the chassis to see what’s inside. It also reflects iFi‘s implied aspiration to be like Apple products — the contents of the interior are meant to be just as presentable as those on the exterior.

The iUSBPower is a series of noise filters of multiple order — RC, RC, RC, LC, LC — I’m not an electronic engineer, so I couldn’t quite decipher what was going on. iFi Audio, however, is keeping relatively tight-lipped about the specific implementation of the iUSBPower‘s noise filters and voltage regulation.

When asked about the super regulator design, Thorsten Loesch, chief designer of the iUSBPower, only mentioned that “the [NE]5532 is used in the super regulator, as there are some unusual circuit configurations that ensure the extremely low noise we get we cannot really discuss the details.” Well, so much for that, but my best guess is that the NE5532 is being used as a voltage comparator, in conjunction with the Toshiba 2SD2012 as the final linear voltage regulator.

All in all, as long as the device does as advertised, I’m fine with whatever implementation is used. iFi actually posted a series of memos justifying the measurable benefits of the iUSBPower, showing that the output power of the iUSBPower was significantly cleaner than any computer laptop or even dry battery.

Power Supply Noise
Though it doesn’t compare the iUSBPower to other audiophile-oriented products, AMR‘s internal measurements of power supply noise show an advantageous distinction between the iUSBPower (green trace) and other conventional power supplies.
(Diagram from: iFi Audio)
On top of that, the included wall wart was also put through the Audio Precision SYS wringer, revealing itself to be a most capable socket eyesore. Lastly, iFi Audio is particularly proud of the iUSBPower’s ability to break ground loops through its ISO Earth switch.
That's a nice wall wart!
That’s a nice wall wart!

To me, whatever the implementation, the iUSBPower most represents a peace of mind — nearly all city officials will tell you that tap water is perfectly fine to drink, and while 0.5 ppm of urea won’t really affect its taste, the thought of potentially drinking it may just disgust you.

With the iUSBPower, you get, at the very least, the satisfaction of running your stuff through reverse osmosis and activated-carbon — it is most definitely cleaner, and even if you can’t taste the difference in your morning coffee, you’ll be able to appreciate the extra care with which this water has been processed.


Firing up the iUSBPower was a breeze — like I mentioned, dirty-in, clean-out. The computer didn’t even bother to notice that it was there. The USB port continued to function just like any other; the iUSBPower was merely a silent interloper that supplied clean power.

On my iBasso D7, there was an instant and obvious difference in the way hiss and hum came through in the unit. Rather than a blurred pop, there was now a spooling up of sound, like that of a capacitor being charged to its fullest. Basal hiss levels were significantly reduced, but most importantly of all, more regular. No longer did hard disk power spikes audibly transmit across the D7.

The iBasso felt significantly more composed in matters of power — while hiss didn’t completely disappear (the iUSBPower is good, but not a miracle worker and cannot overcome your DAC’s own power circuits), it was managed to a level that made much more sense.

For the audio side of things, I had not expected much change, and at the beginning, the differences were indeed subtle, but once a track with bass kicked in, it was clear that the cleaner power denuded the layers of bass articulation normally hidden by hiss and unstable power. Everything <500 Hz felt clearer, more full-bodied, and tauter. The lower midrange, 500-1000 Hz, also seemed to see a bump in transparency.

After switching back to regular computer power, the D7 noticeably thinned in body, and while it appeared to sound more analytical, the detail levels actually decreased. The treble more more jagged than smooth, and decay didn’t feel as natural.

What didn’t change, however, was the line-out. The line-out of the D7 had always been far cleaner than the output of the headamp. The D7 used a reference XMOS design for USB to S/PDIF conversion and the resulting I/V output was weak, but very clean indeed (and probably my favorite part of the unit). I was glad that it was affected negatively in any way, though after hearing very palpable difference with the headphone output, I kind of hoped it’d somehow “enhance” the line-out as well.

The ISO Earth function also didn’t seem to have any type of audible effect, but I kept it on anyway just because it couldn’t hurt. Perhaps I just don’t have the golden ears to pick up on periodic ground loop noise.

Keep in mind that the iUSBPower, while excellent, won’t audibly help all units, especially when the DAC is designed with galvanically-isolated USB inputs, like the Resonessence Labs Concero HP ($850 CAD). The Concero HP’s sound presentation was near unaffected by the addition of the iUSBPower, pointing more to excellent power management on Resonessence Labs’ part, rather than any “fault” by AMR iFi. However, if I juiced up the volume control and connected my most hiss-sensitive earphone, the Final Audio Design FI-BA-SS, I did detect slightly less noise overall.

Results tested from the externally-powered Firestone Audio Custom Cute and Tobby DACs were variable. The Tobby was similar to the Concero HP in that there was little to no benefit. It supposedly powers certain critical components via a small, internal low-noise, regulated DC generator within the box, and the S/PDIF input is isolated from the USB section as well, so power management is already robust.

The more simply-designed Custom Cute exhibited small improvements with respect to bass definition, but apart from that, I couldn’t detect much else. Keep in mind that even though the Custom Cute is a budget DAC unit, it incorporates an isolated USB design, and interestingly accepts a proprietary power input from their own Supplier power unit, designed to provide clean power just like the iUSBPower.

Overall, I found the iUSBPower from AMR iFi Audio to be quite a useful desktop companion for portable devices. It does indeed provide a very clean power supply and rejects power spikes from the computer. So the take-home message is that you should find out if your DAC’s power management is up to snuff — look up its schematics, take a peek at the PCB board (though most manufacturers won’t be as accommodating as iFi in labeling which is what), or just ask the maker, and find out whether power management may be the source of your hiss, hum, or even resolution and transparency issues.

Unfortunately, unlike your drinking water, there isn’t an environmental protection agency monitoring its quality — you have to be the one keeping tabs. So, if your morning coffee isn’t quite delivering that rich aroma you crave, maybe it’s time to put a water filtering apparatus in. In the same way, your sonic taste buds may just thank you for introducing the iUSBPower into your system.

Continue to Part 2: KINGREX uCraft (Y) USB Cable

Published by


Within the Round Window, Between the Helices, Par Excellence.

4 thoughts on “iFi Audio iUSBPower & Kingrex uCraft (Y) Cable | Water for Your Espresso”

Leave a Comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s