Ease of Use
Setting up the GT40 is about as straightforward as it gets, just connect your inputs and outputs and you’re ready to go. Even the USB input is completely self-installing, and connected without a hitch to my Vista OS ThinkPad laptop. The GT40 could handle just about any type of file I could throw at it, although because it tops out at 96kHz/24-bit, those giant 192kHz files aren’t going to play.
The only application that requires a bit more work involves using the GT40 to make digital audio recording from analog input sources (line-level or phono input, as you chose), where you use the GT40’s USB port as a digital output. In that scenario, you do need to go into your computer’s audio settings to adjust the recording resolution, but that’s about it. I used the GT40 with the familiar (and free) Audacity recording software package, and found them to work well together.
The GT40 can be used in several different capacities, so we need to break down the way it handles each task. They say that a jack-of-all-trades is a master of none, but I found that the GT40 was remarkably competent at just about every task, especially when you consider its reasonable selling price.
Because of the way it works, many of the GT40’s functions are impossible to evaluate in isolation. For example, it’s impossible to hear the DAC other than through either the line stage or the headphone amp. It’s only by using it in several different configurations that you can begin to build a mental impression of how each section performs.
GT40 as a USB DAC
This was perhaps the GT40s most impressive area performance wise. Even though it doesn’t employ the currently popular asynchronous interface to communicate with the computer, the sound of files playing through the GT40 would make anyone understand why computer audio is important for the future of high-end audio.
The sound had a vibrant feeling of life and dynamics, with plenty of sock at the bottom end and fine delineation of upper octave detail. Midrange textures were well fleshed out especially with high-rez files, allowing me to follow individual instruments while keeping everything grooving together as a coherent whole. Qualitative differences between 44.1kHz/16-bit and higher-rez 96kHz/24-bit files were quite audible on those recordings where I had access to both. Overall, I would call this a fine performance for the price, even if the GT40 were just a USB DAC without all of those additional functions.
GT40 as a Headphone Amp
I tried the GT40 with a number of different types of headphones including the HiFiMAN HE-5, Ultimate Ears UE-10 Pro custom IEMs, Sennheiser HD-580 and HD-555, and B&W P5, along with several others. I find that by using a mix of headphones I can get a better read on the sonic character of an amp, balancing out the somewhat brightly tinged qualities of the HE-5 against the smooth laid back perspective of the B&W P5. Based on these observations, the GT40 comes across as essentially neutral through the bass and midrange, with just a little softening at the very top end. Bass quality and detail was superb, although high-powered sustained organ pedal notes showed how the GT40 could eventually compress just slightly as it ran short of steam driving the low-sensitivity HE-5s. With nothing playing into the UE-10s there was a fair amount of hiss if you really opened up the taps, but this volume level would have blown eardrums out if a track had started. There was no hum or other type of noise besides the very low level hiss.
GT40 as a Phono Preamp
As a hard-core turntable user I tend to be especially picky when it comes to phono preamps, so I was delighted to find that the GT40’s phono section was not just some slapped on afterthought. While the stepped up gain of the moving coil input worked fine, it was in the lower gain moving magnet position where I found the GT40 would really sing. Coupled to an Audio Note IQ3 cartridge, this combination slotted into my tweaked out analog-centric system beautifully. Sure my Croft tube preamp is a little more refined and less mechanical sounding, and my Vendetta phono stage is way quieter, but the GT40 had an impressive ability to resolve fine detail and put across vivid midrange textures. Low-priced phonostages are often lacking in dynamic swing, but the GT40 had plenty of smack and power to go with its lovely textured midrange.
I did note that the phono stage is quite prone to picking up noise from surrounding components and power supplies, so some care with placement is needed if you plan to use this feature. Simply trying out different orientations and positions while listening through headphones usually resulted in a quiet spot.