USB audio – what ails thee? When audio data makes its way from A, the computer or streamer, to B, the DAC, untouched in all but the most extreme of cases, why worry? Digital audio’s promise is Kindergarten-esque in its simplicity: ones and zeroes fired down a wire. The reality is anything but.
Those ones and zeroes are transmitted in the analogue domain using electrical pulses. Of major concern is jitter – the irregular arrival…timing of…the…audio data. Another challenge is electrical noise minimisation. With downstream electronics’ delicate signal handling disturbed by electrical noise, tonality becomes greyed out and dynamics become weaker. Notably absent in bass punch. Music sounds subtly more ghostly and brittle.
To the rescue have come a steady stream of USB fixer-uppers.
Sitting between PC/streamer and DAC, filters from AudioQuest and iFi Audio work by sending a portion of this SQ-degrading noise to ground.
Alternatively, externally-powered solutions from the likes of Wyred 4 Sound, Schiit, UpTone and (again) iFi Audio cauterise the host PC’s power before re-injecting their own cleaner go juice. Some even reclock the USB signal. The modern day parlance surrounding these USB-correcting products is ‘signal integrity’.
According to Thorsten Loesch of AMR and IFi Audio, deleterious noise doesn’t only hitch a ride on a USB connection’s power line but it can also trouble the signal integrity of its two data lines (D+, D-) and the ground.
According to Loesch, “Via this ground wire ground loops can form, even when there is no audible hum and even when the power is cut completely. Also high frequency noise can travel along all wires in a USB cable and cause RF problems in downstream equipment. And not just the USB DAC itself but the amplifiers following it.”
“There have also been for many years first generation USB isolators offering galvanic isolation, at the cost of blocking most high resolution audio streams due to speed limitations and negatively impact sound quality due to very high level of jitter.”
With the introduction of their latest USB fixer (of which there are now a dizzying array), the iGalvanic 3.0 (US$349) attains the (manufacturer-defined) Holy Grail of USB audio transmission: galvanic isolation with USB2.0 and USB3.0 connections and for hi-res sample rates – up to 32bit/768kHz and DSD512.
Quoth iFi’s promo blurb, “Where others have stopped at USB2.0 galvanic isolation, we started with USB3.0 galvanic isolation and absolutely turbocharged the device for the ultimate in USB audio.”
USB3.0 not only offers faster data transfer speeds than USB2.0 but separates transmitting and receiving lines (shared by a single line with USB2.0).
iFi’s palm-sized iGalvanic 3.0 puts its circuitry in a palm-sized EMI/RFI-shielding aluminium shell to take a streamlined approach to cleaning up USB audio: the host PC/streamer’s USB output goes in and cleaned up USB comes out. In between, the data lines are galvanically isolated so that only digital audio signals are given free passage; anything else is confiscated at the border.
According to Loesch, only galvanic isolation can stop higher frequencies coupling between the RF emission-loaded computer source and the audio system, latter often not great at separating such emissions from the signal. These emissions degrade sound quality.
Loesch again: “Galvanic isolation is a highly desirable feature for USB audio. It is a design technique that separates electrical circuits in order to eliminate stray currents. Signals can pass between galvanically isolated circuits, but stray currents, such as differences in ground potential or currents induced by AC power or RF noise are blocked. In the literal interpretation galvanic isolation means that there is no connection for direct current.”
The heart of iFi’s approach foregoes the apparently standard approach to galvanic isolation, where the signal is deconstructed and reconstructed either side of a bandwidth-limited data bridge, for an in-house developed solution that moves the data whole via an alternative route. A data route bypass then. If that sounds a little vague, feel free to hit up the iFi Audio for more info.
The iGalvanic 3.0 also offers a cleaned up 5V feed via USB’s power line for DACs that need it to run but remains invisible to the host PC/streamer and calls for no additional drivers.
Interceding between a Meridian Explorer2 and MacBook Air 11” (with USB3.0 ports), the iGalvanic 3.0’s does not show up in the MacOS Sound Preferences pane. We still see only the Explorer2.
Without doubt: sounding a shade fuller and a soupcon richer, the Apple laptop’s sound quality as a digital transport feeding the the USB-powered Meridian DAC is improved by the iGalvanic 3.0.
On a scale of one to ten, where one is a Raspberry Pi 3’s stock USB output – the weakest sounding digital transport heard by this reviewer to date – and ten is, say, a dCS Network Bridge, the iGalvanic 3.0 takes the Macbook Air from a 2 to a 2.2. This scoring system is for illustrative purposes only.
In the world of high-end audio where diminishing returns kick in early and hard, a ten percent improvement is not to be sniffed at, even when the dollars don’t quite add up: US$299 for the Meridian, US$350 for the iGalvanic 3.0. Why drop more on the USB fix than the DAC itself?
The answer lies in seeing a digital front end as a combination of DAC and streamer — analogous in relationship to a phono stage and a turntable. Just as the phono stage’s ability to compensate for weaker upstream hardware varies, so too does a DAC’s with a digital source.
Experience tells us that in the majority of cases, a DAC with a higher build budget is more likely to feature jitter- and noise-reduction circuitry of its own.
Reframed in this fashion, I had high hopes for the iGalvanic 3.0 lifting the Raspberry Pi 3’s USB sound quality up above the ground floor when paired with the Meridian dongle. But it wasn’t to be. The Raspi’s 2.0 ports don’t serve up enough power to fire up the iFi device. The downstream Meridian DAC remains silent. No LEDs light up on either unit.
Back to iFi who point to their iDefender (US$45) that slipstreams power from a low noise wall wart like his iPower (US$50) as workaround. Adding these two to the iGalvanic brings our total corrective spend to US$450. Brought to bear on the Raspi 3, the 3 x iFi bundle sounds quite a bit better, going from a 1 to a 2.5.
Our perceptual challenge is not that this iFi three-fer is excessive for a US$38 mini PC but that ALLO’s S/PDIF diverting DigiOne HAT (US$99) comes on as smoother and with greater liquidity for considerably fewer dollars. I’d score the ALLO-loaded Raspi 3’s audio performance at somewhere close to 4. This in turn suggests that ALLO’s USBridge at US$149 will more than likely deliver a superior value quotient than the iFi bundle, even if it does prove to be edged out by the latter on audible performance.
Time to move up market to the Vinnie Rossi LIO for some Destroyer (Kaputt) and Desolate (The Invisible Insurrection) via the KEF LS50 and Sennheiser HD800. With the LIO’s internal DAC module playing D/A converter, the iGalvanic 3.0 once again fills out the Macbook Air’s sound with weightier tonal mass and more robust bass punch. The delta noted was a little more pronounced than with the Meridian Explorer2. In the LIO context, the 11” Air’s USB output is notched upward from a 2 to a 2.5 by the iFi.
With the off-grid LIO I expected to make adjustments to the iGalvanic’s 3.0 earthing via its 3-position toggle that deals with problems arising from multiple earths or none at all. But no. With each DAC and source pairing used for this review, the toggle held its (ahem) ground in the centre position without issue.
In the context of this (almost) fully-tricked-out LIO’s multi-thou street price, the iFi piece makes more financial sense. So too with the Peachtree nova300 whose internal DAC also benefits from a little bit of iFi isolation from the Macbook player.
The iGalvanic 3.0 was then applied to Aqua Hifi’s La Scala MKII Optologic. Despite the Italian showing greater immunity to the iFi box’s charms, it still managed to squeak a little more from the Macbook Air: 2 to 2.1.
Keeping both feet on the ground, we should note that this iFi device cannot work miracles. Applied to the 11” Macbook Air (or a Microsoft Surface Pro 3), the iGalvanic 3.0 takes us only so far before hitting a glass ceiling. It won’t transform a PC or Mac into a digital source capable of the audible richness and ease served up by the Innuos Zenith SE music server (review to come). Nor can the iFi-d Macbook Air (or Surface Pro 3) compete with Sonore’s microRendu (US$640), let alone their ultraRendu (US$875).
Two sharp reminders that the better sounding digital audio transports are usually specialist devices designed from the ground up to minimise electrical noise and jitter.
According to iFi, for the ultimate in their USB corrective services, the jitter-correction and packet noise suppression of their micro iUSB3.0 is also required.
Back to Loesch and co.: “[The iGalvanic 3.0] is a Nano range device so things like power supplies, clocks etc. are not quite of the same high level as those in the iUSB 3.0 micro. The iUSB 3.0 micro remains our “flagship” USB repeater and can be upgraded to offer galvanic isolation by adding the iGalvanic 3.0.”
“For the absolute perfectionist with a reference class, money-no-object system with a +US$10,000 DAC striving for the absolute zenith and wishing to squeeze out the last drop of performance from their system, we recommend complementing the iGalvanic 3.0 with the micro iUSB3.0. This adds additional benefits outside of the scope of the iGalvanic 3.0, such as dual ports and a noise floor of 0.1uV(0.0000001V).” — that last figure is one fifth of the iGalvanic 3.0’s.
“Most, who require the ‘holy grail’ of galvanic isolation, will use the iGalvanic 3.0 stand-alone. Using the analogy of adding an external clock to a DAC, the micro iUSB3.0 compliments the iGalvanic3.0 in a similar vein.”
Separating the iGalvanic 3.0’s standalone contribution from that of the Wyred 4 Sound Recovery (US$199) proved too close to call. That’s high praise given the Wyred 4 Sound dongle’s standing as my preferred device for USB cleanliness. On price, US$150 falls between the two devices. The Recovery wins out on value for money.
Where the Recovery cannot match the iFi piece is on its go anywhere flexibility. A wall wart power supply is required to get the Recovery out of bed whilst the iFi sucks on the host device’s bus power. For yours truly, that meant marginally better sounding MQA-d Bowie (A New Career in a New Town box set) with the Meridian Explorer2 driving a pair of Fitear Air CIEMs, all whilst sat in a hotel lobby with Microsoft Surface Pro 3 on lap. Perhaps we should see iFi’s iGalvanic 3.0 as the goto USB fixer-upper for road warriors.
Whatever the use case, the iFi box delivers on its promise: better sounding USB audio.
Further information: iFi Audio