I could never see why there was any requirement for a USB input on a DAC. I do not tote my music collection around on a laptop. A lot of people do, though, it seems. However, when I decided to convert a raft of vinyl into FLAC to store on my NAS drives, making those albums available to anyone in the hi-fi equipped rooms in my house, the combination of laptop and a USB enabled DAC started to appeal. Especially a DAC with a reverse gear; one that can become an ADC at the push of a button...
Previously, the only USB DAC I had in my possession was the budget champion, the Cambridge DacMagic, although its designer still damned USB technology with the faintest of praise, suggesting you view it as a kind of last resort. Then an Arcam rDAC arrived. Its USB performance was a shade more refined but it still failed to light my fire: it was a little too pedestrian in the toe-tapping and dynamics department. Now, though, I have the fabulous, little £395 Alpha Design Labs GT40 USB DAC by Furutech parked on one of my equipment tables. This nails its colours firmly to the mast by providing a USB connection not as an option or an extra but as its sole means of digital connection. To quote the instruction manual, “The GT40 has been designed... primarily for the playback of PC-based (and Mac-based) digital audio and for the conversion and recording of analog signal via USB to your PC”. To connect the 24-bits/96kHz-capable GT40 to my laptops I acquired a Furutech audiophile USB lead: the GT2, which will set you back £80 for an 0.6 metre length.
The GT40 converter, which Furutech describes as ‘seriously-shielded’, includes a headphone amplifier and a moving coil/moving magnet phono-stage, which you can switch to perform as a line-level input, squished into its compact enclosure. This enables you to add your vinyl collection or tape recordings alongside your CD-rips, downloads and any other music stored on your computer. It also facilitates the use of the line-level output of an external phono stage to optimize the performance of any high quality moving coil cartridge. When ripping vinyl you need every last dB of noise floor that you can get. What is more, I did not especially want to leave my carefully configured Naim Superline sitting silently and pointlessly guzzling electricity when it could be put to good use.
The GT40 is designed to operate from an external power supply because Furutech considers that while regular USB DACs do not need one, any that operates at a higher resolution requires one to offer satisfactory performance. The included supply is one of those far-eastern, parts-bin, wall-warts of the sort that can radiate garbage into the mains in particular. If you encounter such problems or if you are, like me, paranoid about switched mode supplies, around £20 will buy you a suitable, non-switching, regulated analogue supply from Maplins or a similar store that will replace it. (There is nothing intrinsically wrong with switched mode power supplies but their application is normally tuned for charging mobile phones and not high-end audio. The noise they generate is rarely a consideration, while squeezing their cost by another penny is usually a major concern.)
The small number of connections makes hooking up the GT40 a breeze. Select the appropriate input with the MC/MM/Line slider control and connect the turntable (or external phono stage) with a pair of RCA phono terminated leads. Connect the Output sockets to your pre-amplifier for monitoring – or, preferably, when recording vinyl, connect a set of headphones to the front panel jack. Finally connect the USB socket to your computer with a high quality USB Type A-Type B lead and you are set to go. There is one button on the facia that controls the signal direction in the GT40: when depressed it routes digitised music to the USB outlet for recording; when in the ‘out’ position it sends signals from your computer to the DAC and on to your headphones or pre-amplifier by way of the level control.
While writing this piece I happened across what looked like a very well-organized piece of vinyl acquisition software by Acoustica called Spin it Again, which retails at $34.95 (about £22 at the time of writing). I had tried a few similar programs, which for a variety of reasons had failed to satisfy me. Spin it Again, however, was a step in front of most. It even has a metadata lookup facility wherein you type in the artist and album name, and the software hunts down the track names and lengths etc., from an internet database, which saves you having to enter them manually – in the majority of cases. It also helps the program divide the lengthy recorded file into individual tracks, which can save some time. The program does not have the depth or complexity of Audacity, being wizard driven and appearing to be aimed more at the casual user rather than the rabid audiophile, but it does the job and functions smoothly with the GT40. (The software uses the bi-directionality of the device to record and then play back during editing of the recording.) It records up to 24-bit/192kHz WAVs but I stuck to 24-bit/96kHz WAVs, which I then converted to 24/96 FLACs for storage on my NAS drives. 24/96 is the maximum sample rate that the GT40 will handle.
Sounds from my USB 2.0-equipped Acer and Toshiba laptops – played using Media Monkey software – lived up to the claims in ADL’s literature for a sound that is “smooth, detailed, impeccable and very musical.” I fed the output from the GT40 into my active system pre-amplifier. The detail was particularly remarkable for the subtle manner in which it was so clearly revealed: it may have been obvious but there was nothing obvious about the way in which it was presented. Details in the back of the mix, for example, were plainly audible while remaining firmly behind other layers in the arrangement. The ripped sound retained the natural dynamics and persuasive timing of my record playing system as well as presenting the rich instrumental texture of tracks like John Hiatt’s "Drive South". In this song, Hiatt tunes his guitar to a banjo-esque dropped-G, which gives the song an interesting quality especially when he plays alongside Sonny Landreth’s acoustic slide guitar. Hiatt’s droning open strings resonate very agreeably with the timbre of Landreth’s instrument. The vivid dynamics and precise timing of the song can be attributed to the DAC’s preservation of leading edges and its low noise floor. The DAC also rendered his voice with equal feeling and accuracy, and impressed listeners with its articulation and communicative qualities.
Furutech clearly acknowledges that hi-fi is about enjoying music and not just about numbers and measurements. That much is evident as soon as you have the GT40 set up just-so, by which I mean wired with better cables than the standard USB types that come with computer peripherals. Arguments rage about whether a nominally digital cable can influence the performance of an audio system but I am in no doubt that the Furutech GT2 is significantly more convincing and realistic in its presentation than the standard cheapie cables – especially those equipped with Ferrite rings, which do nothing to retain the true vitality of a musical performance. Music sounds temporally more persuasive and crisply defined – with more natural leading edges and decays – through the GT2. The standard cable sounds tolerable, but once you have auditioned the Furutech alongside it, it simply no longer passes muster. It lacks finesse and sounds distinctly lethargic in comparison to the GT2.
All things considered, the Furutech Alpha Design Labs GT40 USB DAC in conjunction with the GT2 USB interconnect looks to be the inexpensive but nonetheless ideal audiophile quality choice for anyone who wants to digitize their vinyl – at up to 24-bit/96hHz – and then play it back from their computer either though their hi-fi system or a pair of headphones. It certainly managed to do justice to my Well Tempered Amadeus GTa, Dynavector XX-2 and Naim Superline setup. Amusingly, in this burgeoning age of computerized, networked music, the prime requirement can still be a top quality turntable, arm, and cartridge!
Alpha Designs Labs (by Furutech) GT40 USB DAC/ADC
Maximum resolution: 24-bits/96kHz
Analogue input: MM/MC cartridge and line-level phono sockets
Digital input/output: Type B USB 2.0 connector
Audio output: line level through RCAphono sockets
Headphone output: 3.5mm jack socket (manufacturer suggests 16 ohm to 300 ohm impedance headphones)
Dimensions: (H x W xD) 6.5 x 15 x 12 cm
Weight: 0.78 kg
Price: £395, $480
Distributor (USA): Elite AV Distribution
Tel: (323) 466-9694
Distributor (UK): Sound Fowndations
Tel: +44 (0)1276 501392