MSRP: £395.00
What is the ADL GT40a?
The Alpha Design Labs GT40a is, on the face of it, either a minor miracle or the answer to a question that nobody asked. This little box is able to act as a phono stage with moving magnet and moving coil cartridge handling, a digital to analogue converter (and indeed analogue to digital converter) and last but by no means least, a headphone amp. Quite why it sprang into existence able to do these varying tasks is unclear but on the face of it, if you need a device to perform more than one of the above roles, it could be something of a star.
Perhaps, given it's origin, the functionality should not be too much of a surprise. Alpha Design Labs is the electronics wing of Furutech and the company has done a good job at exploiting niches in market categories that other brands ignore. The product line-up mainly focuses on the digital side of the divide but their pedigree in headphone amps is not to be sniffed at. The ADL Cruise headphone amp was one of the first such devices in its class, but remains a truly excellent performer with the sort of headroom that few rivals can challenge.
Even so, in the cold light of day, the GT40a looks like it faces a tough challenge. The £395 asking prices pitches it against a wide variety of products and most of those opt to perform a single one of its functions rather than all of them. Can this little box really do all the things it says it does well enough to compete across multiple categories?
Perhaps, given it's origin, the functionality should not be too much of a surprise. Alpha Design Labs is the electronics wing of Furutech and the company has done a good job at exploiting niches in market categories that other brands ignore. The product line-up mainly focuses on the digital side of the divide but their pedigree in headphone amps is not to be sniffed at. The ADL Cruise headphone amp was one of the first such devices in its class, but remains a truly excellent performer with the sort of headroom that few rivals can challenge.
Even so, in the cold light of day, the GT40a looks like it faces a tough challenge. The £395 asking prices pitches it against a wide variety of products and most of those opt to perform a single one of its functions rather than all of them. Can this little box really do all the things it says it does well enough to compete across multiple categories?
Design and functionality
The GT40a is a refinement of the older (and almost identical) GT40. Internally, it is built around a pairing of a VIA VT1736 USB interface and 24bit/192kHz Cirrus Logic CS4270 DAC chip. These are both chips that are less commonly encountered in products of this nature but they have a piece of functionality that makes them relatively unusual in that both are two way devices that offer both digital to analogue and analogue to digital conversion. Used as a USB DAC, the GT40a can decode sampling rates up to and including 24/192kHz. It is compatible with most versions of Windows (except Vista oddly) and versions of OSX up to and including El Capitan. DSD is not supported however.
This hardware can then be used to convert an incoming analogue signal to a digital one to be sent out via the USB connection. As an A-D converter, the ADL has a bit of clear air in its specification over most rivals. It is capable of carrying out this conversion at sample rates up to 192kHz which should give you the required bandwidth to completely capture anything that you happen to send to it. A-D conversion is a fairly specialist area and the GT40a is simultaneously one of the most affordable models to offer it and perfectly competitive in specification terms too. If you are looking to encode an analogue signal to digital, this is a fairly cost effective option.
The party piece of this encoding comes courtesy of the on board phono stage though. As well as the digital circuitry, the GT40a comes with a phono section that is entirely separate to the digital part- in other words, play a record and send it via the analogue outputs and no interaction with the digital section will happen at any stage. It can handle moving magnet and moving coil cartridges and this is selected via a two position switch on the rear panel- another switch removing the phono stage entirely from the circuit. The ADL is a fixed loading design in that you cannot adjust the loading or capacitance but at this price point this is not too unusual. The loading as designed will support any standard moving magnet cartridges and the bulk of moving coil ones too.
This hardware can then be used to convert an incoming analogue signal to a digital one to be sent out via the USB connection. As an A-D converter, the ADL has a bit of clear air in its specification over most rivals. It is capable of carrying out this conversion at sample rates up to 192kHz which should give you the required bandwidth to completely capture anything that you happen to send to it. A-D conversion is a fairly specialist area and the GT40a is simultaneously one of the most affordable models to offer it and perfectly competitive in specification terms too. If you are looking to encode an analogue signal to digital, this is a fairly cost effective option.
The party piece of this encoding comes courtesy of the on board phono stage though. As well as the digital circuitry, the GT40a comes with a phono section that is entirely separate to the digital part- in other words, play a record and send it via the analogue outputs and no interaction with the digital section will happen at any stage. It can handle moving magnet and moving coil cartridges and this is selected via a two position switch on the rear panel- another switch removing the phono stage entirely from the circuit. The ADL is a fixed loading design in that you cannot adjust the loading or capacitance but at this price point this is not too unusual. The loading as designed will support any standard moving magnet cartridges and the bulk of moving coil ones too.
This combination of features means that the GT40a is a great archiving tool. We've looked at two turntables that are able to do vinyl ripping on board- the Pro-Ject Essential Phono USB and Audio Technica AT-LP5- but both of these are limited to 44.1kHz rips with a moving magnet cartridge. The GT40a can be used to rip with a higher quality moving coil cartridge at 192kHz which should notionally at least remove all digital noise to outside of the audible part of the signal. Alpha Design Labs doesn't provide any ripping software but Audacity will work perfectly well with it.
The final aspect of the GT40a makes the business of ripping an analogue source easier and adds the last bit of functionality. A full size headphone socket and volume control is fitted and this allows the GT40a to do two things. The first is act as a conventional headphone amplifier for either a USB, analogue line or vinyl source. The second is that the headphone socket can be used to monitor the output of any recording in a way that can be extremely difficult with other vinyl ripping solutions. Like the phono stage section, the loading of the headphone amp is fixed but given the recommendation for partnering equipment is between 16 and 300 ohms, you shouldn't have too much trouble finding partnering models.
All of this wizardry is then compressed into a small metal chassis 15cm wide, 6 high and 11 deep. The casework is all metal and extremely well finished with a level of integrity that isn't often found at the asking price. Special mention has to go to the volume control which is a machined metal knob and that manages to feel lovely in use while offering commendable fine adjustment at the same time.
The final aspect of the GT40a makes the business of ripping an analogue source easier and adds the last bit of functionality. A full size headphone socket and volume control is fitted and this allows the GT40a to do two things. The first is act as a conventional headphone amplifier for either a USB, analogue line or vinyl source. The second is that the headphone socket can be used to monitor the output of any recording in a way that can be extremely difficult with other vinyl ripping solutions. Like the phono stage section, the loading of the headphone amp is fixed but given the recommendation for partnering equipment is between 16 and 300 ohms, you shouldn't have too much trouble finding partnering models.
All of this wizardry is then compressed into a small metal chassis 15cm wide, 6 high and 11 deep. The casework is all metal and extremely well finished with a level of integrity that isn't often found at the asking price. Special mention has to go to the volume control which is a machined metal knob and that manages to feel lovely in use while offering commendable fine adjustment at the same time.
Positives
The extensive range of functionality effectively puts the ADL in a class of its own. There is no rival product that can do what it does in the footprint it occupies at the price it costs. When you then consider that in specification terms at least, very little seems to have been cut in terms of the hardware that the GT40a uses to perform this functionality. This is an awful lot of product for the money.
The extensive range of functionality effectively puts the ADL in a class of its own.
Negatives
The GT40a is in a class of one and the more cynical amongst you might be thinking that this is because it is a combination of roles that very few people have actually asked for. While it is perfectly logical to combine a DAC with a headphone amp or a phono stage with analogue to digital conversion, putting all it into one box is a more specialised proposition. The other area of the GT40a that needs to be taken into account is that although it does a great many things, it cannot easily be asked to do more than one of them at once. Using the ADL as a phono stage requires the connections to be used in such a way as to preclude switching it straight over to use as a USB DAC for example. As such, while you can kill a few birds with one stone using it, you can't kill them all at once.
How was the ADL GT40a tested?
The ADL has been used in a variety of contexts. For testing as a USB DAC, it has been connected to a Lenovo T530 ThinkPad running jRiver and using a variety of lossless and high res FLAC files. Phono stage testing has been done with an Avid Ingenium Twin turntable fitted with an SME-M2 tonearm and Audio Technica AT33 PTG/II cartridge on one side and an Audio Note Arm III tonearm and Nagaoka MP-150 cartridge on the other. In both cases, the GT40a has been connected to a Naim Supernait 2 integrated amplifier and Neat Momentum 4i Speakers. Headphone testing was carried out using the Beyerdynamic T70 headphones from last month's review with the GT40a running in USB DAC mode.
Performance as a USB DAC
With the Furutech decoding jRiver from the Lenovo, the first thing that is apparent is that the volume control on the front never leaves the circuit. Turning a volume to maximum is the accepted way of removing such a control from the circuit but it is worth noting that doing so with the GT40a gives you truly monumental gain- more of that in a bit. Aside from the volume however the Alpha Design Labs manages to do an awful lot right. It sounds smooth and natural but simultaneously avoids sounding rounded off or safe while it does so. There is plenty of punch to the sound as well.
Listening to the high res FLAC of Peter Gabriel (3) (Melt) shows the GT40a to good effect. The ADL does a fine job with vocals and manages to create a convincingly three dimensional reproduction of the recording. The bass is also extremely impressive with a pleasing sense of depth and impact partnered with enough detail and texture to not simply sound like a dull thud. There is a slight sense that the Alpha Design Labs delivers most of what it does with CD resolution material and doesn't necessarily deliver a huge amount extra when used with high res, but given that high res is still very much in a minority of most people's listening, that should not be a huge problem. There is also a very slight lack of warmth in the midrange that means that when you are listening to something delicate, the GT40a can sound very slightly sterile.
For the most part though, this is a powerful and lively sounding device that packs a real punch to it. The lack of DSD support will possibly deter buyers that purchase on the on paper spec (although given how 'out there' the spec of the GT40a is, most of them are likely to have decided against it for different reasons anyway) but for PCM and SP/Dif, this is a very likeable DAC.
Listening to the high res FLAC of Peter Gabriel (3) (Melt) shows the GT40a to good effect. The ADL does a fine job with vocals and manages to create a convincingly three dimensional reproduction of the recording. The bass is also extremely impressive with a pleasing sense of depth and impact partnered with enough detail and texture to not simply sound like a dull thud. There is a slight sense that the Alpha Design Labs delivers most of what it does with CD resolution material and doesn't necessarily deliver a huge amount extra when used with high res, but given that high res is still very much in a minority of most people's listening, that should not be a huge problem. There is also a very slight lack of warmth in the midrange that means that when you are listening to something delicate, the GT40a can sound very slightly sterile.
For the most part though, this is a powerful and lively sounding device that packs a real punch to it. The lack of DSD support will possibly deter buyers that purchase on the on paper spec (although given how 'out there' the spec of the GT40a is, most of them are likely to have decided against it for different reasons anyway) but for PCM and SP/Dif, this is a very likeable DAC.
Performance as a headphone amp
The news that the GT40a doesn't fundamentally alter its presentation through headphones should not be too surprising. The same lively, powerful and detailed presentation is present and once again, if I'm being very critical, there is a slight lack of engagement and warmth in the midrange although the GT40a once again sounds fast, lively and effortlessly free of any sense of compression or softness.
In the context of headphone use, the GT40a's hefty output is more of an advantage. It has no trouble hitting a substantial listening level with both the Beyerdynamic T70 and the fairly insensitive Oppo PM-3. Furthermore, high levels are free of strain and harshness and the overall noise levels are low to the point of non existent. The physical volume control also makes for a very easy adjustment of the level to exactly the one you want rather than something approximating to it. Compared to the Chord Mojo, the ADL can come across as a little congested but in some ways it sounds livelier and punchier than the Chord does and has the benefit of a full size headphone socket.
In the context of headphone use, the GT40a's hefty output is more of an advantage. It has no trouble hitting a substantial listening level with both the Beyerdynamic T70 and the fairly insensitive Oppo PM-3. Furthermore, high levels are free of strain and harshness and the overall noise levels are low to the point of non existent. The physical volume control also makes for a very easy adjustment of the level to exactly the one you want rather than something approximating to it. Compared to the Chord Mojo, the ADL can come across as a little congested but in some ways it sounds livelier and punchier than the Chord does and has the benefit of a full size headphone socket.
Performance as a phono stage
It seems a little surreal to stop using the GT40a as a DAC and plug a turntable into it but doing so is simple enough to do. Having done so, the performance of the GT40a as a phono stage is perhaps the biggest surprise of this little box. For starters, that whopping gain ensures that it doesn't really matter what cartridge or amplifier you are using, the ADL should be able to give you the listening levels that you are looking for. Then, as a further bonus, even with the gain levels set very high, the GT40a is a very quiet phono stage indeed. If your deck is naturally free of hum, the Alpha Design Labs won't add anything to it.
Once you start playing records, the news is equally as good. The GT40a motors through Art Angels by Grimes in a manner that is similar to the performance with digital but with some subtle differences too. With both MM and MC cartridges, the GT40a is a little warmer and more involving than it is with digital, but never sacrifices the punch and drive that it demonstrates elsewhere. The bass response in particular is deeply impressive for a phono stage at this fairly sensible end of the market and the same detail and texture that really helps the believability is present here too. Spend a bit of time with the GT40a as a phono stage and it becomes clear that this section is not an afterthought or a convenience feature and does instead really deliver at a competitive level. As I find the process to be generally miserable, I didn't try a vinyl rip but other user reports online suggest that the process is as straightforward as it can be.
Once you start playing records, the news is equally as good. The GT40a motors through Art Angels by Grimes in a manner that is similar to the performance with digital but with some subtle differences too. With both MM and MC cartridges, the GT40a is a little warmer and more involving than it is with digital, but never sacrifices the punch and drive that it demonstrates elsewhere. The bass response in particular is deeply impressive for a phono stage at this fairly sensible end of the market and the same detail and texture that really helps the believability is present here too. Spend a bit of time with the GT40a as a phono stage and it becomes clear that this section is not an afterthought or a convenience feature and does instead really deliver at a competitive level. As I find the process to be generally miserable, I didn't try a vinyl rip but other user reports online suggest that the process is as straightforward as it can be.
Spend a bit of time with the GT40a as a phono stage and it becomes clear that this section is not an afterthought or a convenience feature
Conclusion
Pros
- Brilliantly flexible
- Powerful and involving sound
- Well built
Cons
- Can only really do one thing at once
- No DSD support
- Slight lack of warmth
Alpha Design Labs GT40a DAC & Headphone Amp Review
Even after spending a fair bit of time with the Alpha Design Labs, I can't in all honesty tell you if this is an inspired way of making the largest Venn diagram pleasing product possible or something that simply does too much to consistently appeal to all parties. What has become abundantly clear though is that nothing on the GT40a is an afterthought or convenience feature. This is a very capable DAC, an impressive headphone amp and a brilliant phono stage. It is naturally possible to select single function components that can deliver more outright performance in a single category but the margin they have over the GT40a is less than you might think and none of them offer the ability across different categories. This then is a Swiss army knife of audio and if you have a requirement for such a thing, this is a very clever little device indeed.
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