GT40 as a Digital Recording Interface
This is probably the most difficult part of the GT40’s performance to isolate, because you have to play the recorded file back through the GT40 (or another similar device) to hear what you have done. Having said that, when I recorded from LPs it was not too difficult to hear the improvements as you went from a CD-like 44.1kHz sampling frequency to the highest available 96kHz rate. The sound became more liquid and transparent, with a notably improved sense of contrast in the fine high frequency detail. Even at 96kHz the GT40 couldn’t quite fool me into thinking I was listening to the direct analog recording, but it was still perfectly enjoyable and engaging as a listening experience.
I played a lot of music during my time with the GT40, but some highlights are worth noting.
“Song for Bassanio” from the soundtrack to the 2004 movie version of The Merchant of Venice [Decca] pairs a boy’s treble voice against a lute. Playing the ripped CD through the GT40 into my Audio Note amp and Quad ESL57 speakers, it was really quite difficult to differentiate the file playback from spinning the CD directly. The plucked strings of the lute had exactly the same attack and resonance played either way, and treble Ben Crawley’s voice sounded just as crystal pure through the GT40 as from the CD player. Towards the end of the short track a string section enters, and from the CD I felt there was a tad more dimensionality, but even this was a close call.
I played the track “Words of Wonder” from Keith Richards’ Main Offender album [Virgin Records] from the PC over the HiFiMan HE-5s, and found thunderous reggae style bass line could cause the GT40 to run a little short on power if you really cranked it up. While the amp didn’t audibly clip, there was a slightly compressed quality that would take some of the pop out of drummer Steve Jordan’s wickedly powerful rim shots. When I switched over to the much easier to drive UE-10s this slight dampening of the transient speed disappeared, and sound regained its familiar jump factor.
I transferred the track “Goodbye Pork Pie Hat” from Charles Mingus’ album Mingus Ah Um on SACD [Sony], using the analog outputs of my Oppo universal player into the GT40’s analog line input. I transferred it three times, using the 96kHz, 44.1kHz, and 32kHz settings (skipping 48kHz), and compared the results. The 96kHz version was really very close to the SACD, with just a little of that “direct from tape” solidity and smoothness missing. However, with the 44.1kHz version the differences became clearer, with the spit in Booker Ervin’s sax harder to separate out from the overall tone of the instrument, and a diminished sense of space around the individual players. I should note, however, that these differences really have more to do with the DSD vs. PCM debate, than any performance issues with the GT40.
Consider this product if:
You want to build a computer audio-based system, but also have legacy analog sources that you want to listen to or archive digitally. While it does work great in the context of a full-sized home audio system, the GT40 really comes into its own for the headphone or desktop audio listener.
Look further if:
You have digital gear with only an S/PDIF (coax or optical) interface that you want to incorporate into your system. ADL has an upcoming product called the Esprit, which adds this feature, but also loses the GT40’s phono stage. You should also keep looking if you have very low impedance or ultra low sensitivity headphones that you treasure. Some other amps have more ultimate driving power than the GT40.
• Tonal Balance: 8
• Clarity: 9
• Dynamics: 9
• Output Flexibility: 10
• Value: 10
The GT40 shows us that a jack-of-all-trades really can be the master of all. While it might not get hard-core audiophiles drooling to use it in the most extreme megabuck systems, I’d be hard pressed to name any product that can clearly outshine the GT40 in just one of its many functions for the same money. When you add all of those functions together, the result is clearly a bargain.
Alpha Design Labs/Furutech GT40 USB DAC/ADC, phono stage, headphone amp, line preamp
Accessories: Power supply and USB cable
Frequency response: 20Hz - 20kHz, (+0.5db @ 40Hz, -0.5db @ 15kHz)
THD + Noise: S/N ratio -90db (A-weighted, line output)
Analog Inputs: Phono cartridge (MC/MM); line level on RCAs
Digital Inputs: USB 2.0, type B connector
Analog Outputs: Line level (single ended RCA); ¼ inch headphone jack
USB DAC: Up to 96kHz/24-bit
Digital Outputs: USB 2.0 up to 96kHz/24-bit
Input Impedance: 47k Ohms (MC/MM phonon), line (no spec)
Headphone output impedance: Headphones with 16-300 Ohms impedance recommended
Headphone power output: 80mW @ 32 Ohms
Power supply: 9 Volt wall wart-type
Dimensions (H x W x D): 2.25” x 5.94” x 4.17”
Weight: 28 ounces
Warranty: 1 year, parts and labor