Audiophilleo 1 and 2 USB-SPDIF converter review

[This review has been a long time in gestation. Why? It takes several months’ solid listening to get to grips with a DAC’s personality. Even more time is needed to be convinced of changes further up the source chain.]

Regular readers will know my first truly revelatory experience with USB converters arrived with John Kenny’s battery-modded Hiface. So profound were the improvements over and above my first love – the Squeezebox Touch – that I ditched said Logitech device in favour of a MacBook as computer transport. I’ve since upgraded to a 2010 MacMini and now run the (headless) Squeezeslave daemon for 16/44 material (as I can’t give up on Squeezebox Server’s iOS-fuelled library navigation) and Audirvana or Fidelia for hi-res music files. Artwork, tagging and folder re-structuring are all now handled exclusively by Dan Gravel’s excellent Bliss.

I’ll give the game away from the very beginning lest doubters fail to sit up and take notice from the off – the Audiophilleo is a breakthrough device. The importance of clocking data timing before it is fed into your DAC – as well as fencing off a computer’s electrical noise emissions – are not to be underestimated. Both of these impact on the sound that emanates from your speakers. That said, little at the source end is as dramatic as the way loudspeakers differ in flavour. The reader (that’s you) needs an a priori acceptance that a reviewer’s (that’s me) emphatic manner is a way of making clear my expression of difference and then underlining its importance (and not necessarily the magnitude of said differences).

You might have a DAC and find yourself underwhelmed by the (lack of) engagement with music. Does your digital audio experience sound anaemic? Opaque? Tense? Jitter and electrical detritus are the two most likely culprits. If you’re using a computer as transport you may benefit from a USB-S/PDIF converter, of which there are plenty to choose from. Squeezebox/Sonos users currently have fewer (two!) options: the Firestone Audio Bravo or the Audio-gd Digital Interface.

DAC manufacturers love to tout their products’ ‘vanishingly low jitter’ or ‘high jitter immunity’ (or similar sword brandishing from marketing departments). Fair enough – BUT – why then the need for USB-S/PDIF converters such as the Musical Fidelity V-Link (AU$199), Audio-gd Digital Interface (US$190), MHDT USBridge (AU$195), M2Tech Hiface/Evo (AU$195/AU$449) or Halide Bridge (AU$549)? These products aren’t just conduits between computers and DACs-sans-USB; they’re trying to take jitter and noise levels down further. Clearly, the existence of these converters imply that the inherent jitter/noise handling of most budget DACs isn’t as good as it could be.

Philip Gruebele sells direct from the USA. His Audiophilleo product is offered in two versions. The Audiophilleo1 (US$950) has all the bells and whistles: OLED screen, volume control and jitter simulator (among others) and is available in a range of nice case colours. The Audiophilleo2 (US$579) comes in a plainer grey-metallic shell – no bells, no whistles – but retains the sonic DNA of its flashier sibling. The extra cash for the Audiophilleo1 brings the unit to your door by way of a mini suitcase (WITH a Wireworld USB cable and external PSU); the Audiophilleo2 ships in a standard cardboard box which contains a more standard USB cable. Both ship with BNC-RCA adaptors. The commentary that follows applies to either model (unless specified), but to my mind – as they both sound identical – the better bang for buck lies with the Audiophilleo2.

The aim of Audiophilleo unit is to extract digital audio from a computer source (via USB) and then present the cleanest S/PDIF signal possible to a DAC. The Audiophilleo tackles this with a two-pronged approach: data re-clocking and power regeneration. Dual clocks – one for 44.1/88.2/176.4 and one for 48/96/192 – ensure that there is no clock synthesis (as found within Musical Fidelity V-Link); possibly the main reason why the Audiophilleo sounds convincingly superior to the V-Link with Redbook material.

Asynchronous USB transfer also helps greatly in keeping jitter from creeping into the mix; but we can’t be 100% certain this is why the Audiophilleo nudges out the Audio-gd Digital Interface in terms of audible performance gains. The DI takes a broom to jitter – via async data handling – once it is inside the device (and not at the gates). Both are different takes on the asynchronous recipe. Readers are advised to stay alert and stand firm against the hypnosis of the asynchronous USB crew: the computer can still make timing errors even when the receiving device calls the shots. Asynchronous USB implementations might erode a significant amount of jitter but there’s no guarantee that they will exponge all of it – that’ll be down to the quality of the design and implementation. As is always true, you’ll need to listen for yourself to be certain of a device’s (paper-promised) performance. I’ve heard superb sounding adaptive USB DACs (db Audio Labs Tranquility SE) as well as underwhelming asynchronous USB DACs. Pragmatism matters.

Whilst we’re talking jitter stats, the little American unit emits “8ps or less RMS phase jitter 10Hz to 100Khz” – impressive. Philip Gruebele knows he’s onto something and has provided a handy comparative matrix. Again: don’t rely on the numbers to form a judgement – go listen!

One-upping the M2Tech Evo, the Audiophilleo offers USB class-compliant 24/192 playback on Mac/Linux. You plug it in and away you go. Windows users will require drivers for anything above 24/96 (available from the Audiophilleo website), but that’s a Microsoft thing and nothing that can be laid at Gruebele’s door. As the Audiophilleo works with standard USB drivers it can also be serve as converter to an iPad (via the camera connection kit and powered USB hub). Note that iOS is limited to 24/48 playback.

Computers are notoriously noisy digital transports. RMI/EMI noise gets transmitted down the USB cable, the amount of which will vary from computer to computer and can be CPU load dependent. This electrical garbage often makes it all the way into the receiving DAC. Hiface modder John Kenny takes out the trash by feeding the Hiface with 5V of battery juice . Philip Gruebele takes a different approach. The Audiophilleo offers galvanic power isolation from the USB’s electrical noise and – instead of relying on an off-the-shelf S/PDIF output stage – Gruebele has designed a custom output circuit:

“Differential logic is the best way to implement low-jitter designs. The Audiophilleo S/PDIF clock and output circuits make extensive use of differential ECL components. This approach uses somewhat more power, but enables very low levels of jitter.”

“The output circuit is galvanically isolated from both the computer and rest of the Audiophilleo, which allows coupling to the DAC without the use of an output transformer. In turn, this helps prevent ground loops which can reduce performance. The output stage also features high “return loss” below 20 MHz, so that any internal reflections are minimized; it also exhibits very clean edges, with little ringing.”

Another neat trick pulled by the Audiophilleo its negation of the need for a digital interconnect. This little box connects directly to your DAC’s BNC or RCA input connector. You need not worry about cable type, length or – best of all – budget. You side step the cable (reflections) debate in its entirety.

Should you demand a far more technical exposition of what’s behind (and inside) the Audiophilleo1/2, read (and read again) Nicholas Bedworth’s superbly thorough coverage at 6Moons.

One thing that Bedworth didn’t tackle was the nature of sonic changes that unfurl from deploying this matchbox between computer and DAC. Having had the sexed-up Audiophilleo1 knocking around these parts for several months, it’s done several tours of duty with many DACs: Audio-gd Reference 7.1, Anedio D1, Beresford Caiman Gator, Project DAC Box FL, Emotiva XDA-1 and the Rega DAC. The Audiophilleo improves the sound of ALL of them, each to varying degrees, and – in some cases – narrowing the differences between them. Generally, the cheaper DACs bore witness to the most significant improvements. Little difference was noted when the Audiophilleo was applied to the PSAudio PerfectWave DAC (over and above a direct USB feed).

The first, most pronounced improvement is in tonal colour. That washed out anaemia is all but erased. Music sounds less fragile and less stressed – with the Audiophilleo music has the solidity of oak beams. ‘Assured’ and ‘confident’ are two appropriate descriptors. The second most obvious lift is with bass reproduction. Initially, I’d misinterpreted this as ‘more bass’. I later corrected myself: with the Audiophilleo bass boasts tidier, more complete definition.

In broader terms, a mountain chair-lift is given to immeasurable (subjective!) qualities such as coherence, truth, conviction and elegance. Music is more definite and emphatic via the Audiophilleo. Simply put: it’s like moving from a biro to a fountain pen.

Even horribly compressed recordings benefit. The sinister moog sound that haunts the corners of Arcade Fire’s “Rococo” finds more space in which to advance and then retreat. It sheds its George Romero zombie skin to reveal the human player beneath.

Over a number of weeks, the Audiophilleo was compared to John Kenny battery-fuelled Hiface, now in Mark 3 iteration and henceforth known as the JK MK3. Readers hoping for advice on which way to swing will be disappointed. There isn’t much to split them. The Audiophilleo possibly pulls ahead with more transparent acoustic bass texture, but only with some material. The bass that anchors Elvis Costello’s Cohen-esque “After The Fall” is one example where the lower frequency definition of the Audiophilleo2 is more obvious. With the electronic kick drums of Extrawelt remixes the differences don’t manifest themselves so obviously. The JK MK3 might just have the better way with smoothness, the Audiophilleo cleaner and more lively. These differences are anything but cut and dried.

More tech-focussed consumers might also wish to consider ‘integer mode’. In essence, it’s a computer transport’s ability to strike up a DIRECT conversation with the USB converter (or DAC) WITHOUT using the uppermost layers of the operating system as a go-between. You’ll need a software player that supports integer mode – currently only Audirvana and Pure Music for OS X do so – and a hardware device that also supports it. The Audiophilleo supports integer mode but the M2Tech Hiface does not. (A continually updated list of other devices that support integer mode can be found over at this Computer Audiophile post.)

If you have 16/44 music files, they should be played back at 16/44. That’s bitperfect. If you upsample 16/44 to 24/96 inside your computer’s operating system (or software player), they are no longer bitperfect. If you use an software player volume control and – depending on the extent of attenuation – music sent to the DAC might no longer be bit perfect. At time of writing, integer mode is broken in OS X Lion and Apple-heads are advised to stick with Snow Leopard.

Some more theory. Playing back 16bit audio via a 24bit software setting sees the original 16 bits padded with an additional 8 bits. The theory states for every -6db of attenuation we lose a single (least significant) bit. One would have to attenuate -48db before volume attenuation wipes out the 8 bit padding. Whilst not true to the definition of bitperfect, no data is lost…until we move beyond -48db.

However, it’s probably best to set your software music player of choice to full volume and therefore feed the Audiophilleo bitperfectly. Leaving the Audiophilleo1 fixed at 0db facilitates ‘direct’ mode and ensure that the bitperfect data makes it all the way to the DAC. The Audiophilleo1 also has a menu option that allows the user to test bitperfect status using the sample files available at the Audiophilleo website. The Audiohilleo1 displays the sample rate and bitrate received on its vibrant OLED screen. With no such screen, the Audiophilleo2 communicates the sample rate and bit rate via a series of LED flash codes (which require greater user attentiveness).

Examining the device in a broader context, the Audiophilleo doesn’t have ANY feature-list shortcomings – it ticks every box. Much of the competition comes up at least one feature short: the M2Tech Evo requires a BYO power supply, the Musical Fidelity V-Link contains only ONE oscillator (48/96 family), the Audio-gd DI doesn’t offer asynchronous USB reception and the MHDT USBridge requires custom drivers. The Audiophilleo2 is over twice the price of of the Musical Fidelity and the Audio-gd – getting what you pay for holds (mostly) true. Having heard both the V-Link and the DI, neither match the Audiophilleo’s tonal colour saturation and broader coherence. Of the two, the Audio-gd box gets closest.

It ain’t just the luck of the Irish then. Gruebele’s Audiohilleo is every bit as impressive as John Kenny’s battery-modded Hiface. Those committed to an off-the-grid approach should probably opt for the JK MK3, IF they can live with remembering to flip the recharge switch after listening and don’t mind the digital interconnect cable dance. The Audiophilleo is for those who want a set-it-and-forget-it approach. It’s also a device for those waiting on the asynchronous/buffer creases to be ironed out on the Squeezebox Touch’s USB output. As soon as John Swenson has it sorted, the Touch will be given a new lease of life in this reviewer’s main rig. Remember: the Audiophilleo runs on native Linux USB drivers and the Squeezebox Touch runs Linux. It’s not a matter of ‘if’ but ‘when’.

All of this slowly swirls to an emphatic conclusion. Much like the JK MK3, the Audiophilleo is near-mandatory for digital audiophiles looking to get the best from their computer as digital transport. Cut a hole in your DAC budget and factor one in…at least until manufacturers start building this technology into their DACs (which they currently do not). This is one tiny box that ensures that your audio diet is tasty and nourishing. DAC manufacturer marketing spiel be damned: if you use a computer and a (budget) DAC as your digital front end, an Audiophilleo should be your next purchase. 100% essential.

Associated Equipment

• MacMini 2010
• Audio-gd Digital Interface + PSU
• Musical Fidelity V-Link
• JK MK3
• Rega DAC
• Anedio D1
• Pro-ject DAC Box FL
• Emotiva XDA-1
• Audio-gd Reference 7.1
• Beresford Caiman Gator
• Exposure 2010s2
• Leben CS300XS
• Zu Omen
• ProAc Tablette Reference 8

Audition Music

• Mercury Rev – Deserter’s Songs Instrumental (2011)
• Arcade Fire – The Suburbs (2011)
• Extrawelt – Darkroom Dubs Remixed (2011)
• Elvis Costello – Mighty Like A Rose (1991)
• Leonard Cohen – The Future (1992)

Further Information

• Audiophilleo