Review: NAGRA TUBE DAC no-compromise D/A converter

Review: NAGRA TUBE DAC has all the qualities that are decisive for its choice by any hobbyist looking for a first-rate D / A converter.
3.8/5 - (15 votes)

Nagra TUBE DAC and the significance of a supreme digital source

In the course of any hobbyist’s audiophile journey, we have all conversed and sometimes even argued about the importance of each element in an audio system chain in its final sound. Most of those consulted always say (leaving the room aside of course) that loudspeakers are the most influential element of any system and, being in agreement, I can also disagree. How is this understood? In my opinion, in an entry-level or mid-level system, I have no doubt that this statement is correct, but the higher we raise the level of our system, the more important the sound source is, until it becomes the key to the whole. Nothing good can come of a poor sound source, whatever the price or quality of the amplification or the speakers we use. Even a D / A converter like this Nagra TUBE can raise the sound quality of any system so much that we may not even recognize it. As a reflection, let’s raise the quality of our sound source, whatever its format, before changing other components that may not perform as well as they can due to a defect in the origin of our signal.


My testing of the Nagra HD DAC in 2015 rediscovered the legendary Swiss firm and was a revelation for me as to what I want from a digital source. I liked this DAC so much that I ended up getting it and enjoying it to this day. But time passes, Nagra has advanced dramatically in its developments and has released a replacement for my beloved HD DAC. Actually I consider that Nagra is at the best moment of its success story when it comes to home audio. In recent years, the launch of its full HD range on the market has meant that it can compete with the most prestigious amplification brands in the world, and its successful commercial strategy and alliances in international shows with leading brands, has placed Nagra as benchmark among the most elitist electronics.

After the launch of the HD DAC model in 2014, Nagra brought out another superior DAC, the HD DAC X, as part of its superior HD LINE. That is why it was convenient to change the name of the HD DAC so as not to create confusion by not being included in its star series and taking advantage of improvements derived from its superior model, it took out its replacement, our protagonist TUBE DAC included in its CLASSIC LINE.

But what differences do we find between our TUBE DAC model and the previous HD DAC?

NAGRA TUBE DAC Technical characteristics

The differences do not remain in a name change and a specific improvement that justifies it, but they are profound and in almost all areas of its design. Let’s describe them:

  • The TUBE DAC converter extends the resolution with which it works, adopting its circuits the DSD 4x (Direct Stream Digital 256), operating with the highest resolution that exists today, 256 times that of a standard CD and four times that of a SACD.
  • The analog section has also been the subject of unrestricted focus. Traditional steep slope filters have been totally eliminated. As a result, transients and harmonics are preserved, thus making music sound exceptionally natural. Key design elements include ultra-superior performance controllers, hand-wound transformers, and a valve-actuated output stage.
  • The equipment is powered by 25 extremely low noise precision internal power supplies. In this way, each element has its own and truly independent supply source. The Nagra TUBE DAC converter requires two external power supplies, one for the digital section and the other for the analog section, and keeps the two sections isolated independently. It must be paired with the Nagra CLASSIC PSU for maximum performance, although it is also compatible with the Nagra MPS, the previous generation power supply.
  • The TUBE DAC converter has wide connection possibilities to be able to be integrated into all types of home and professional systems. It is especially suitable for computing environments thanks to its next-generation USB audio input. Through it, it receives signals up to the DSD 256 format from a PC or Mac.

As for the design of the Nagra TUBE DAC, it is practically the same as the previous HD DAC model, varying only a small selector on its front that was previously in charge of silencing the unit -Mute- and now it has become a phase selector -although in the same place and same size so as not to change its shape. On the back we find 2 x S / PDIF (RCA and BNC), 1 AES / EBU, 1 optical, 1 USB (mode 2) and 1 x I2S (Nagra format) digital inputs and 2 pairs of RCA and XLR analog outputs.

The power supply does change to a greater extent: more weight and size, fewer LED lights and it is not compatible with the incorporation of a battery inside as its predecessor was. On this occasion, a bank of super capacitors increases its performance according to the company.


The realm of this Nagra TUBE does not belong to that of the pure and crystalline sounds that are usually analyzed and consumed by inveterate audiophiles, those that feed on that high end that melts with infinity or with those low frequencies that often collapse our listening room. When a component draws our attention to an aspect of the sound it reproduces, it is that it shows deficiencies in its overall tonal balance. Incorporating the Nagra TUBE into our system is a step towards getting closer to the “reality of music”. These are very thick words that deserve an explanation to be understood. The most noticeable effect that I have felt when I have installed the Nagra TUBE in my system is to be aware that until that moment the music I was listening to had a degree of harshness or dryness, of which I was not aware, and that limited my sensitive experience. The music comes to life with the Nagra TUBE suddenly appearing juicy, much fuller with sounds, with more harmonics, and thus gained in size, density and richness.

Sometimes we confuse dry bass frequencies with being very controlled and this is not true at all. Wandering a bit, I realize that “dryness” almost never brings good things: not in food, not in our body (eyes, mouth, etc.), and sex, better not to talk … Any engine needs to be well lubricated , and music achieves this through natural resonances and harmonics, in short, sounds that make music as rich and beautiful as it is. This task is carried out by this Nagra TUBE to perfection, since returning to the low frequencies, they sound round, with a lot of detail but at the same time with weight and intensity, nothing anemic. The lowest frequencies of the sound spectrum are the base where the rest of them rest, and if we try to get as close as possible to analog sound, our bass must be complete and solid. But the rest of the frequencies enjoy the same level of quality and realism.

How not to highlight the middle zone in the same way, which so seductively hypnotizes us and makes us stick to the couch listening to album after album. Salvador Sobral’s latest album, entitled “Alma Nuestra” is a good example of this. Part 4, “Tú me accustomed”, a version of the bolero written by Cuban musician Frank Domínguez, serves to certify what has been expressed so far. With overwhelming bass frequencies, full of the necessary detail to “witness live” the beating of the percussion that sets the rhythm at the beginning of the track, hoping that the delicate voice of Sobral will let us see a quality in the media of the first level, a delight…!!! Presence that impresses us without overwhelming us, color in the ringtones without a hint of additional sweetening (and the fact is that a first-rate tube electronics is increasingly far from the usual cliché of coloration). In short, only realism and a lot of naturalness, can you ask for more?

The highest notes keep the perfect balance between going unnoticed thanks to their perfect balance and integration with the rest, but showing full of detail, smoothness and harmonics. An easy resource is to stand out by excessively highlighting the high frequencies (many brands fall into that trap that has a short travel in my opinion), when the really honest thing and of course more complicated is to present a balanced sound. That is the key to this Nagra TUBE, respecting the balance that live music has, being faithful to the recording that we want to reproduce but transmitting emotion and magic in each listen. No matter what files we play, whether it is CD quality or high resolution in any of the multiple formats it supports, the result is always great.

The sound scene is unbeatable, with a first-class width, height and informational density, not being necessary to resort to high resolution files to enjoy that extra in size and grandeur that we sometimes perceive with them. The quality of playing CDs is so high that it makes us revalue the treasure that our collection of compact discs keeps inside and its absolute validity. I also acknowledge that I am a regular user of a tandem transport / DAC, because to date nothing sounds like that to me. In my opinion, after many tests, my preference in digital playback is my transport mechanics playing CDs, then an audio server with internal storage and finally streaming playback from digital platforms.


Responsible for this opulent soundstage is sure to be your new CLASSIC PSU external power supply. With a chassis size and weight much higher than the previous MPS, you just have to take a look inside to appreciate that we are dealing with a power supply that has nothing to envy that of a power amplifier of considerable power.

The CLASSIC PSU gives this DAC the necessary authority to sound with an absolute level of reality. The impact, the micro and above all macrodynamics, the scenic size and an appreciable sufficiency at all times, is in my opinion the biggest difference and quality leap between this fabulous TUBE DAC and the previous HD DAC.

I cannot and should not conclude my analysis without referring to the option of using the volume control of the TUBE DAC and using it as a preamplifier connected directly to my power units. I should not be the one to question the need to offer this possibility, but I think that whoever has the budget to undertake the purchase of this DAC should have a high-flight preamplifier in their system. In any case and given that we are in a moment of trend of the most compact and less intrusive systems, it may be of interest to many fans.


Unfortunately for the TUBE DAC, replacing my Ypsilon PST100 MK2 preamp is not an easy task, as in my opinion it is one of the best preamps on the market. Despite the pressure of this “almost impossible” mission, the Nagra came out with his head held high from this trap. Does it sound as good or better than the previous Ypsilon? The truth is that no, but it is close enough that any fan who arrives on a budget to configure a high-flying sound system, can consider using it as a preamplifier / DAC as long as he does not need more analog inputs of course. Its sound is somewhat hotter or more romantic than my Ypsilon preamp which can sometimes be wonderfully or tyrannically raw with its realism. In the same way, its dynamics is a little more limited, although respecting a very similar level of detail. In short, its sound can be described as a bit more valvular in the classic sense of the term, but with first-rate detail and resolution. The Nagra’s remote control, although not the most exclusive, being able to afford a posh metallic remote control, works perfectly with speed and precision.


NAGRA TUBE DAC Conclusions

The Nagra TUBE DAC has all the qualities that are decisive for its choice by any hobbyist looking for a first-rate D / A converter. Apart from offering a wonderful, organic, natural and detailed sound in abundance, supporting practically any available format and resolution, it has the advantage over the competition of offering a brand value, a timeless aesthetic and the “glamor” that all products of the Swiss Nagra possesses that makes it practically irresistible.

Its price alone may discourage future buyers, but unfortunately as with everything quality has to be paid for and with the Nagra TUBE no one can be disappointed. I can only dream of what the company’s absolute flagship DAC, the Nagra HD DAC X, will sound like, but that’s another different experience, which of course I would like to savor in the future. For now I only aspire to enjoy this Nagra TUBE for a few more days before I leave my home. I will stay with the memory of being the DAC that has most connected with my emotions of all those who have passed through my system. I cannot recommend it more warmly as it is a gem.