Audio Note Cobra tube amplifier Review
Until recently, Peter Kvortrup scolded all-in-one solutions, hated USB interfaces, did not think about creating a combine (an integrated amplifier with a digital-to-analog converter on board) and did not allow the appearance of really powerful devices in the lower (for the Audio Note) price category. The ice broke on all fronts at once – the new Audio Note Cobra tube amplifier is equipped with a built-in DAC with USB input, and develops 27 watts per channel, and costs a little less than $5000. Fantastic? No, reality – but how the device will show itself in practice, we will now analyze.
Integrated tube amplifier Audio Note Cobra came in a discreet cardboard box, traditional for the company, but in a double and rather dense one. The instructions are just as austere – however, the amplifier itself seems so simple and elegant that even a child can install it. The main thing to remember is that the device is quite weighty, like any tube amplifier – with a case dimensions of 340x199x451 mm, it weighs 13.6 kg. The output power of Audio Note Cobra when operating on a load of 8 ohms reaches 2×27-28 W (the data in the operating instructions differ slightly from the official website), the error in the entire operating frequency range is 0.3 dB. The power consumption of 175 W clearly hints at the correct power parameters of the amplifier section.
The preliminary amplification stage for each Audio Note Cobra channel is implemented on a 5670 double triode and a 6AU6 pentode, the power amplifier is built on a pair of EL34 pentodes from the American company Electro-Harmonix, manufactured at the Sovtek plant in Saratov. The amplifier operates on a push-pull circuit, has an input impedance of 100 KΩ and an input sensitivity of 300 mV. The rear panel contains three analog line level inputs (on RCA connectors) and three digital ports.
Unfortunately, the problem is present at the most widespread USB input today – the device can only receive signals up to 16 bit / 48 kHz through it. The optical input is much better – it works with digital streams with a resolution of up to 24 bit / 96 kHz, and the best digital connection is the coaxial input, which is capable of accepting a signal with a resolution of up to 24 bit / 176.4 kHz. It should be noted that the heart of the Audio Note Cobra digital-to-analog converter is the good old Philips TDA1543 microcircuit. Its real resolution parameters are 16 bits, so the issue of differences in the resolution of the signals received at the input refers only to the conversion modules and the quality of the interfaces, and not to the physical circuit of the matrix. One way or another, the chip can still operate on only 16 bits. Although, during our experiments, it was the coaxial connection that provided the best results – again, due to the interface solutions.
Other features include a set of proprietary output transformers with a double C-core – this approach, together with a push-pull circuit, guarantees sufficient power to drive even complex speakers. The finishing touch is the finish. The austere signature design of the amplifier seems impeccable, but only the black color scheme slightly reduces the possibilities for integrating the Audio Note Cobra into your room design. During operation, like all tube technology, the device, of course, heats up a lot – so when installing it is worth leaving enough free space around the amplifier.
As for the control, there is nothing to complain about, the volume is smoothly adjustable – the accuracy of the regulator allows you to set the desired level, the input selector is relay here, and the quality of the switching terminals deserves applause. Another distinctive feature of the Audio Note Cobra is the presence of a remote control in the kit, which cannot be called typical for a tube amplifier. And even if, apparently, this is a universal remote control, the quality of performance of which is discordant with the level of the amplifier itself, the ability to make it louder without getting up from your sofa is worth a lot.
After the first turn on, Audio Note Cobra will not be able to demonstrate anything intelligible – the device needs to warm up. In our test room the device worked for several days – and its sound quality was constantly improving. Immediately after switching on, the new amplifier produced only a caustic and flat sound, which had nothing to do with the corporate style.
On the second day, Audio Note Cobra began to show its noble facets. The stage has received volume and holography, the bass has become detailed and textured. An important point – the low notes performed by Audio Note Cobra never showed “thumping”, on the contrary, the character of the presentation was dry, precise and not dominant. The amplifier was easy to control with our set of speakers – both Klipsch, Sonus Faber, speakers were for it. In the future, the sound of the device improved not so dramatically – and it became possible to draw basic conclusions about its presentation and character.
Of course, Audio Note Cobra is strong in terms of vocal reproduction. The voices of the performers literally materialized in the room, revealing the full range of emotions and richness of shades. That Louis Armstrong, that Lana Del Rey – the texture of the author’s presentation seemed flawless, and the timbre characteristics did not cause any reason for criticism. The device also perfectly echeloned the scene, the images did not overlap and form a proper (albeit not too large-scale) panorama. Yes, there is room to grow in scale – but let’s pay attention to the price tag of the amplifier.
It is worth noting that Audio Note Cobra has a slightly dark presentation of the material, there is no sparkle and high-frequency brightness here – so, fans of “bright” sound may not be very satisfied. On the other hand, muted highs, together with exceptional microdynamics and decent macrodynamics, ensure that plasticky British sound, deep and heartfelt. In short, the handwriting of Peter Quortrup, for which the company has earned cult status.
Oddly enough, but this circuit and a set of lamps are excellently controlled not only with jazz and light classics – the amplifier does not give up on rock, playing well both Led Zeppelin and Dire Straits. It is only necessary to select partners not too “heavy” in terms of input parameters for the amplifier with sufficient sensitivity and without dramatic drops in resistance. Unless at Metallica it seemed to us that the apparatus was beginning to sound less transparent and accurate. On the other hand, Audio Note Cobra is exceptionally strong at low volume levels – its playback character does not change at all.
Audio Note Cobra breaks perception patterns and violates prohibitions. The amplifier offers a well-recognized flexible sound signature of the British company and a lot of features, it may well become the only and main component in your system (you will have to add only the speaker and the streamer). The quality of the production is excellent, the sound is charming – what Audio Note fans have been waiting for for so long has happened.
- MAXIMUM OUTPUT 28 Watts per channel
- VALVE COMPLEMENT 4 x EL34/2 x 6AU6/2 x 5670
- DIMENSIONS 340(w) x 199(h) x 451(d) mm incl. valves, knobs and connectors
Cobra is equipped with three analogue stereo inputs, and an additional three digital inputs, via the onboard DAC. The digital coax inputs can accept signals up to 24-bit/176.4kHz (native bit-depth for the Philips TDA1543 D/A converter chip is 16bit, so anything above this is truncated down). The Optical SPDIF input can accept signals up to 24-bit/96kHz (see above). The USB input can accept up to 16-bit/48kHz.