April 2016


iFi Audio Micro iUSB3.0
The ongoing benefits, and perhaps some controversy, of re-clocking digital audio data.
Review By Clive Meakins

  For some the iFi Audio micro iUSB3.0 as reviewed here and its ilk is a controversial device. I'll accuse it of having a mouthful of a name but otherwise for myself it's not controversial at all. This is another Swiss Army Knife from iFi Audio; I previously reviewed another multi-purpose device – the iFi micro iTube whose functions are multi-faceted as it's a buffer or preamp depending on how you configure it. The iFi Audio micro iUSB3.0 is useful for computer (file-based) audio using an external DAC connected via USB. This covers the vast majority of lossless computer playback in hi-fi systems. This latest Swiss Army Knife improves on the functionality and performance of the original iFi micro iUSBPower.

The iFi Audio iUSB3.0 reviewed here uses a number of methods to do two fundamental things:
1. Clean up the USB data feeding your DAC.
2. Provide a clean 5V power source for DACs which USB use power for some or all of their functions.

That all sounds fine and dandy but a trawl around some of the HiFi forums will reveal a small but very vocal contingent who espouse that "bits are bits" and nothing special is needed for digital playback. Some seem blinded by 0 and 1 being simple and incorruptible but is a hi-fi system really that simple? Unfortunately not. Yes USB is wonderful for transferring files to a printer and I don't see people saying that files are corrupted when transferred over USB, but playing music is not like printing a document. There is scope for electrically noisy computers infecting the ground plane of the downstream DAC, not only is the ground noisy but the +5V supply will be quite unpleasant too. Noise on the DAC ground plane may not impact the digital section of the DAC but DACs have an analogue section too; this is not somewhere we want to inject noise. Even if your DAC is not USB powered or does not use USB power for its USB card, there's a good chance the DAC ground will still connect with the USB ground. A clean ground is goodness. Then we have the re-clocking and general cleaning up of the USB data stream. We're not talking about correcting any data errors but instead this is about making the data easier for the DAC to handle and getting the electrical impedance right. Bear in mind that the data (music) you're playing from your computer transport does not carry timing information; this is something the DAC has to figure out. It seems that regenerating clean data helps a good number of DACs.

I'm in the camp that believes the software player used has a profound effect on the sound I hear. I wish this weren't so, I really do. Computers are horribly noisy things and it seems that software players can alter the sound we hear by using simplified render loops and very specific instructions from the machine's instruction set. This is a massive topic but I have heard the effects with my own ears. The absolute fix for these playback issues is to build a special purpose computer with linear power supplies and running a cut down operating system. Some use the Raspberry Pi which is quite decent but can be bettered by Windows players such as Jplay and the Japanese Bug Head. The world is not ideal; we don't have easy and low cost access to high quality streaming hardware though I daresay this will come along. In the meantime those of us not into building our own hardware can reap huge benefits from using specialist playback software and using the likes of the iUSB3.0 to clean up power and data over USB. Whilst iFi use a switched mode plugtop power supply called the iPower they take a lot of care to ensure it is quiet and then they work on filtering the power yet more, they say they have achieved a very quiet 0.1uV, which is extraordinarily quiet.

This box of tricks also implements iFi Audio's IsoGround which can be selected to be Off or On, this is optionally breaks the ground connection to the computer in a way that is USB standard compliant. Talking about standards, iFi are embracing USB3, this device is fully USB3 compliant and well as being fully backwards compatible with USB2. A short USB3 cable is provided with the unit, this again will work with USB2 as well. There is also a power mode switch, this controls the power from the iUSB3.0 such that it can switch power on/off in synchronization with the PC or it can permanently powering its USB port so for example a battery powered DAC can be left on charge. The outputs of the USB3.0 follow iFi's previous practice, there is an output with just the power lines connected and another with data + power, this allows cables such as the iFi Gemini to used where the power lines are in a physically separated cable to the data cables, this I find has benefits presumably due to reduced transfer of noise between power and data lines. Not only are there a pair of power and data ports, there are two of each so you can connect network attached storage and your DAC via the USB3.0. You could even run two DACs or a DAC and charge your phone.

Does The iFi USB3.0 Live Up To Its Promises?
Checking out the impact of the iFi Audio USB3.0 involved quite a lot of swapping around of DACs, drivers and cables. For most of the serious comparisons I used the Bug Head Infinity Blade player with WAV and FLAC files. I used three DACs to cover the most common power configurations:

1. iFi Audio iDAC2 – this an iFi USB powered DAC meaning that the digital and analogue sections take their power from USB. Even with iFi's excellent power filtering I would expect any remaining noise to have audible effects.

2. Metrum Octave MKII – this DAC has its own linear power supply for main DAC but the USB card is powered by the USB, there is significant USB power filtering in the DAC and there is also galvanic isolation implemented. I have previously found this DAC to respond very well to an iFi power supply feeding the internal USB card, especially in terms of bass performance.

3. Ciúnas – this battery powered DAC by John Kenny is an excellent performer, it takes no power from the USB, instead it uses internal LiFePO4 batteries.

iFi Audio iDAC2
First up I should say more about the iFi Audio Gemini USB cable. This is a double-headed cable which physically separates USB power and USB data. One cable handles data and the other handles power; they then come together at the USB type B plug which is the one that is inserted into your DAC. The Type A and Type B plugs are very solid machined metal affairs with the purpose of screening RFI. There are ferrite cores which can be slid along the cables in the event these help with RFI, each RFI situation is different so a tuneable option is good to have.

I started out with the iDAC2 powered by my laptop USB. The DAC certainly sounded good, this was no surprise given the editor's recent review of the DAC. Compared with the original USB powered iDAC I felt the iDAC2 was a considerable step up. This suggested that the DAC has been significantly improved, part of this is bound be down to the latest iFi experience and developments around implementing highly effective filtering of what is invariably very noisy USB power and electrical ground. I should mention that I mostly used the DAC is set to Bit Perfect mode which means it operates as a Non-Oversampling (NOS) DAC.

Next I introduced the iFi Audio iUSB3.0 and iFi Audio Gemini USB cable. It was immediately apparent there was more inner detail; low level sounds deep in the mix were much clearer and more easily distinguishable versus being lost in the mix. The sound was more open with a greater sense of ease. The bass if anything exhibited a lighter touch but importantly listening to bass notes plucked on a double bass when were adjacent to each other on the musical scale, it was now possible to properly discern the individual notes rather than their merging into one amorphous sound. The soundstage had opened up too, previously hi-hats had been locked to the tweeters left and right, now they were floating properly between the speakers.

All-in-all I'd say the iFi iUSB3.0 with matching Gemini USB cable adds palpability to music making the iFi iDAC2 more sophisticated. It certainly makes the iDAC2 sound like a much more expensive DAC.

Metrum Octave MKII
This is my trusty NOS DAC. I'm very aware that to give its best it needs a dedicated power supply for its internal USB card. Most of my time with this DAC over the last couple of years has been spent with the USB card being powered by the iFi iUSBPower, this I found was vital, primarily for improving the bass. Substituting the iFi Audio iUSB3.0 to power the USB card and perform re-clocking duties brought definite improvements. As with the iDAC2 I found hi-hats moved to be between the speakers, bass was better defined and there was more of a "carpet" of bass acting as a really solid foundation to music. Aggressively played wind instruments now sounded enthusiastic with much less blare or glare. Against their iDAC2 I'd say the Octave was more breathy with saxophone. In all other respects I concluded that the iDAC2 and Octave when powered and re-clocked by the iFi iUSB3.0 sounded very alike and in some areas the iDAC2 just shades the Octave.

I had to try one last thing with the Octave; the iFi Audio iDAC2 has an S/PDIF output so it can act as a USB and S/PDIF converter. Running the iUSB3.0 into the iDAC and then feeding SPDIF to the Octave resulted in the best of all worlds. Where the iDAC2 has been so good, so was the Octave and where the Octave scored with its breathy sax victory this too was retained. I have a sneaking suspicion these successes are down to the iFi implementation of the XMOS USB interface and the iDAC2 handling of the digital signal.

Ciúnas
Here we have a DAC running on batteries, not using any USB power though it does connect the input USB ground. This would be mainly a test of the iFi iUSB3.0 re-clocking capabilities. The differences I heard were in line with much of what I heard with the other two DACs which use USB power. The differences weren't so pronounced but nonetheless they were still there. The iFi Audio iUSB3.0 made the sound coming from the Ciúnas richer and smoother, detail was not thrown in your face but it was still there, in other words yet again it was more sophisticated sounding. Central focus too was improved. Listening to Wynton Marsalis' trumpet was a gorgeous experience as it was with all the DACs auditioned with the iFi iUSB3.0, without the iFi Wynton's trumpet could on occasion be a little pain inducing.

Some Competition
The iFi USB3.0 is not the only game in town, there is also the John Swenson designed $175 USB REGEN produced by UpTone Audio. Kudos to UpTone for being first to market this type of device. As it happens I possess a REGEN and had been using it for some time prior to this iFi review. The REGEN provides substitute power for DACs needing USB power and re-clocks the USB signal using a USB hub circuit. The REGEN and downstream DAC benefit from your swapping in a decent linear power supply rather than using the "get you started" wallwart which ships with the device. I therefore used a linear power supply with the REGEN. The high level concepts of the REGEN and USB3.0 are quite similar.

I used the REGEN via the Octave DAC to set the initial standard as this is what I have been using and was very familiar with. The tricky part of this comparison is that I can't differentiate between improvements due to the linear power supply with the REGEN vs the re-clocking functionality of the REGEN. Prior to using the REGEN I used the original iFi iUSBPower, which does no re-clocking.

I use a couple of different open baffle speaker setups, one is more forgiving of poor recordings, the other is more "explicit" sounding. With the forgiving open baffles it's hard to detect much difference in sound between DAC+iFi Audio USBPower (the original iFi Audio power device) and DAC+Regen. With the explicit sounding open baffles it's easier to pick up on what REGEN brings; greater clarity, more natural sibilance, cleaner upper treble (hi-hats and tinkly sounds), there's greater separation and delineation between sounds. Bass is a little tighter and therefore subjectively a touch leaner too. Trumpet and piano are smoother too.

How Important Are The Improvements Brought By The REGEN?
Is it worth it in my system? Yes. Is it indispensable? No but it's nice to have and at $175 it's not expensive. Yet the USB powered USB card within the DAC clouds the issue in that I can't be sure whether the linear power supply or re-clocking are the cause of the improvement in sound. With the Ciúnas DAC the REGEN made a difference but it was less significant than when the REGEN was paired with DACs needing USB power.

The REGEN was my baseline for auditioning the iFi Audio iUSB3.0. I tried all three DACs – iDAC2, Octave and Ciúnas with both REGEN and iUSB3.0. The result as the same each time though to differing degrees. The iFi Audio USB3.0 gave a richer and smoother sound with fine detail presented in a less forced manner. Bass with the iFi was mostly more powerful, there was also slightly better central focus. Listening to Wynton Marsalis' trumpet on his album with Eric Clapton I found Wynton's trumpet a trace sharp with the REGEN whereas the iFi made this difficult instrument sound more balanced. The REGEN gives a slightly "etched" sound versus the iFi iUSB3.0. The REGEN certainly brings improvements but the iFi offers further improvements.

To Re-Clock Or Not?
If you use a USB connection with your DAC then you need to try the iFi Audio iUSB3.0. I'm sure there are computers or streamers which are so well sorted in terms of noise that re-clocking may not help much, if at all. Most of us using USB probably use a standard desktop or laptop, invariably this will benefit from re-clocking unless you have a very expensive and special DAC which makes itself immune to external noise. I say give the iFi iUSB3.0 a try. Well done iFi!

Specifications
Type: USB re-clocker and digital audio 'cleanup' device
Output Voltage: 5V +/-0.5%
Maximum Output Current: 2.5A
Output Noise Floor: 0.1uV(0.0000001V)
USB 3.0: Ultra-speed 5.0Gbps
Input Voltage: AC 100 – 240V, 50/60Hz (iFi iPower included)
Power Consumption: < 15W (includes powered USB device)
Dimensions: 158 x68 x 28 (LxWxH in mm)
Weight: 285 grams (0.63 lbs)
Warranty: One year parts and labor
Price $399

Company Information
ifi Audio 
E-mail: contact@ifi-audio.com
Website: www.iFi-Audio.com