t's ironic, but the most interesting things happening in the Compact Disc player market segment are taking place at a time when the format had already been definitively rendered obsolete by most audio manufacturers and is considered a "descending" by the music companies. The solutions proposed by companies associated with the format for years, for example: the C.E.C. and Reimyo allow you to achieve sound quality of a CD which one could only dream of looking enviously at what performance turntables and tape recorder offered.

Even sooner similar signals began to come out of the SACD (Super Audio CD) camp – a super-niche format, which survived mainly thanks to the passion of some people in Japan and fantastic NEO-VRDS drives made by Esoteric. This format's revitalization, however, was possible only because of popularity of high-resolution file players, including those capable of playing DSD (Direct Stream Digital) files. At first it seemed that it wouldn't be affected by this race towards higher and higher numbers that took place in the PCM (Pulse Code Modulation) camp, but now if the DAC doesn't decode the PCM up to 384 kHz and 32 bits resolution it is "outdated." And yet ... pretty soon new DACs were introduced capable of not only decoding DSD64 (ie the basic sampling frequency the SACDs are encoded with), but also DSD128. Now we are talking about DSD512 which translates into a sampling frequency of 22.5792 MHz (512 x sampling CD frequency).

Decoding DSD

Decoding a DSD signal seems pretty straight forward – many currently produced PCM DACs provide an interface that allows them to “accept” also a DSD signal. The technical specification of such chips usually mentions their "compatibility" with the DSD signal. If you take a closer look you will find out that such statement is based on a lot of good faith, a bit of naivety and a lot of cynicism. Virtually all currently produced D/A Converter chips are of multi-bit Delta-Sigma type; including the Ring-DAC, a converter designed by dCS. This means that a single-bit DSD signal must be converted to a multi-bit one and only then it can be converted to an analog signal.

I remember perfectly that, when I worked for the "Sound & Vision" magazine, I received for a test the DX-SX1 Sharp SACD player (it was some time around 2002). Its sound was fantastic - as it turned out, not only due to the excellent chassis, fantastic transport mechanism, but in large part due to the great, one of the last ever produced 1-bit DAC chips. It was based on the experience gained by Philips, that already in 1987 introduced Bitstream DACs, which were true one-bit systems. They had their advantages, such as better small signals linearity, however, there were some issues, too. The audio world took a different direction, following the revolution of home cinema systems.

Today, firms betting on SACD and/or DSD try to deal with it in a different way. One example of an interesting solution is the Multiple Double Speed DSD (MDSD) from Accuphase, which works as a low-pass filter, greatly simplifying the system, and among those coming from small companies I could point out the Bulgarian APL, which for years has proposed converters that convert PCM signal to DSD, upsample it to DSD128 and only then the signal is decoded (more HERE). It is worth to note that first man in Poland that made “DAC-less” conversion of DSD signal alive was Mr. Łukasz Fikus of LampizatOr.

A year ago, however, I heard again about a solution that was supposed to eliminate an active converter from DAC. The solution was proposed by Polish company Amare Musica. Almost at the same time a similar concept was introduced to me by Gerhard Hirt from Ayon Audio. The DSD signal can be decoded using a relatively simple analog filter composed of resistors and capacitors, and no other additional chips/circuits are needed for that. Of course, to make such DAC compatible also with the PCM signal, it must be equipped with a PCM / DSD converter. That's the idea behind Tube DAC DSD.

Tube DAC DSD

From the practical point of view it is simply just another "DAC" with a simplified operation. There is no display, no input selector, it is just a silver "cube". Well, not exactly a cube – a characteristic truncation on the front make the shape similar to the one of a diamond, which is also confirmed by the name of the series this device belongs to. The USB port is the key input, accepting PCM signal up to 384 kHz and 32 bits, and - above all - DSD up to Octuple DSD, ie. DSD512. There are also classic PCM signal inputs - RCA (S/PDIF) and XLR (AES/EBU), accepting only the PCM signal, and "only" up to 192 kHz and 24 bits.

The device looks very solid, because it is made from perfectly matching 10 mm aluminum plates. Proper care was also taken about vibration damping – DAC features manufactured specifically for Amare Musica, Ceramic Disc Tablette by out good friend from Franc Audio Accessories. And this is an important feature of this device since the output signal is amplified using electron tubes. This is a balanced design with both, balanced (XLR) and unbalanced (RCA) analogue outputs.

The digital circuit features actually only digital D/D converters, that convert one type of digital signal to another. It works just the same for USB input as well as for RCA and XLR ones. The former "unpacks" PCM and DSD signals and sends it to the circuit that converts signal to DSD. Also a signal from the RCA / XLR inputs is converted. If, however, the device receives a DSD signal it is sent directly to the passive filter.

MACIEJ LENAR
An owner and designer

Designing and building a DAC, which would meet today's customer requirements is a real challenge. Our idea to interfere as little as possible in the digital signal and avoid using of traditional DAC chip required us to wait for an appearance of newer technologies on the market. The solution came with AKM4137EQ DAC from Asahi Kasei Microdevices, which was finally introduced to the market. It met our requirements and helped us to design a DAC without a classic DAC chip. Yes, it is possible.
The input PCM/DSD signal from USB, S/PDIF or AES/EBU inputs is converted inside AKM4137EQ chip to DSD signal. Then it enters the R2R filter and passive filter of the first order. The advantage of this solution is, in our opinion, a very analog sound.

To even deepen the benefits of sound obtained from the digital section of our device we decided to utilize a tube analog stage using a differential amplifier with a current source and repeaters. Members of 6DJ8 / 6922 / E88CC / 6N23P family are perfectly suited for the job. Stabilized power supplies for analog and digital sections complemented the properly designed circuit. Anodized housing milled on a CNC, a flightcase in which the device is packed, anti-vibration feet made by Franc Audio Accessories and above mentioned advantages mean that one has the feeling of communing with a device of a much higher price range..

After one installs USB drivers (S/PDIF and AES/EBU require no drivers) Tube DAC DSD is ready to go – no adjustments, no settings, just “plug'n'play”!

I used Ancient Audio Lektor AIR V-edition as a CD transport and PC HP Pavilion dv7 (JPlay, Windows 10, 8 GB RAM, 128 GB SSD + 520 HDD) as files transport for Tube DAC DSD test. I played both, CDs and music files. The latter were mostly DSD ones, some of them also DSD128. But I listened to a lot of 24/96 and 24/192 PCM files too.

Playing CDs was no different from using a classic player of this type. With files it was somewhat more difficult. First I needed to install the driver, available for download from Amare. Once installed, it turned out that the high resolution files delivered a much lower volume than a CD played with a player – there was a few dB difference between them. A DSD files were even quieter. A lot depends on the settings on your computer, but you have to reckon with a pushing the volume knob higher than usually. Perhaps a better choice would be a dedicated music server.

Albums used for the test (a selection)

Compact Disc

• Deep Purple, Now What?!/Now What?! Live Tapes, EAR Music 0209064ERE, 2 x CD (2013);
• Frank Sinatra, Songs For Swingin’ Lovers!, Capitol/Mobile Fidelity UDCD 538, gold-CD (1956/1990)
• Franz Liszt, Agnelle Bundervoët plays Liszt, Decca France/Sakuraphon SKRP33020, CD (1955/2015)
• Michał Wróblewski Trio, City Album, Elite Records 11529024, CD (2014)
• OMD, Music Complete, Mute Artists/Traffic Japan TRCP-200, CD (2015);
• Pet Shop Boys, Super, Sony Music Labels (Japan) SICX-41, CD (2016)
• Schubert, Song Cycles, wyk. Nathalie Stutzmann, Inger Södergren, Erato/Warner Classics 4623701, 3 x CD (2014)

Music files Aretha Franklin, Aretha’s Gold, DSD64 | Billie Holiday, Body And Soul, DSD64 | Cream, Disraeli Gears, DSD64 | Depeche Mode, Black Celebration, PCM 24/48 | Dire Straits, Brothers in Arms, DSD64 | Elvis Presley, Elvis is Back!, DSD64 | John Coltrane Quartet, Ballads, DSD64 | John Coltrane, Blue Train, rip z DVD-A, PCM 24/192 | Kate Bush, 50 Worlds For Snow, PCM 24/96 | Klipsch Tape Reissues Vol. II, DSD128 | Tomasz Stańko, Wisława, PCM 24/88,2

Japanese issues available at

Let's not kid ourselves - it IS a specialized product. I could keep this statement for the end of the test to sum it up with a strong, catchy slogan, but delaying something that has to be said anyway doesn't make much sense: the Tube DSD DAC is designed, optimized, fine-tuned in order to play: (1 ) files (2) of high resolution, preferably (3) DSD. This belonging to the Diamond Series converter very nicely deals with a signal delivered using S/PDIF cable from a CD transport and its performance with standard CD resolution files is also very good. But what makes music breathe and live are mostly hi-res files, especially DSD ones.

When I used CDs as signal source the performance was smooth and free of sharp edges. Since I tried to spot any problems with treble in particularly adverse conditions, ie. with albums with a strong signal compression and "dirty” treble, I reached for the last OMD and Pet Shop Boys albums. The latter is not so bad, but still it is meant for listening in the car and by small headphones from your smartphone. DAC changed the way the sound was presented. There were no hard edges, nothing “jump out” of the mix, the treble wasn't harsh. The presentation was actually quite nice, ie., it gained some depth, it wasn't just a flat wall of sound. Also, the colors' differentiation seemed better - and with this type of music it is a welcomed feature because it shows changes in the instruments. The rhythm was also nicely preserved, timing was good which one of the key elements of the music.

With high-quality recordings two things were happening simultaneously: one on hand all these actions "ennobling" sound, on the other their side effects. The former meant emphasizing an acoustic background, or ambiance and harmonic background of the recordings. Since there is no hard, clear leading edge, elements from the background play a bigger role than when same recordings are played by more detailed, more selective devices which in fact sort of skip these elements. I mean nice harmonic relations, something under the direct sound, which "glues" the presentation together in a meaningful way.

This way of presenting music works best with of classical music and jazz recordings. Everything is smooth, soft, does not attack listener. A powerful, active bass and good pace and rhythm prevent this presentation from blending into a “hot soup”, that would make it difficult to differentiate individual ingredients. I would rather compare it to a tasty cream with lots of toppings. Vocal recordings sounded simply fantastic as they were particularly enjoyable and natural sounding. Same goes for tracks with lead instrument placed in front of the rest of them.

Every time I replaced one disc with another, I had the impression that the DAC simplified presentation, making different recordings sound similar, "trimming" them to the same punch. An extremely nice, you could even say beautiful one, but always the same. This impression came from a lack of proper differentiation and a roll off the treble. This element of the performance shall draw an attention of everyone, even those without proper experience. I think it will be as easy to identify slight warming of medium and low bass. That made different albums sound nice, enjoyable, that's why they never sounded "thin" or dry. On the contrary – the Amare Music DAC soaked/enriched the sound, which emphasized its dynamic and tone texture.

By doing so it unifies the presentation. ALL CDs played with it sounded nice, smooth, sometimes really delicate (though not entirely, because the bass is strong and unambiguous). A tone modification is also clear – there is a roll off of the top frequencies that is a result of a mitigation of the attack rather than lowering its level. There is also a detectable emphasize in the midrange. The latter can be heard eg. in the female voices that seem to have the range from around 500 Hz emphasized. With some recordings it creates sort of a over-representation of the vocal over instruments, in some others it highlights some of their nasality. In contrast to the devices, that warm up midrange (which Amare does not do) voices are not pushed forward and are not enlarged. All elements of the presentation have the right volume, the proportions are preserved, but still voices sound in a more distinct way.

Listening to the first hi-res file changes this situation almost beyond recognition. What had been pleasant, nice, very safe, now becomes ambiguous. It is clear that with such a signal this DAC delivers a different, very sophisticated performance. It does not try to bring us closer to sonic signature of an analog master tape as these, above mentioned D/A Converters by CEC and Reimyo do. It does something else – it proposes a new, original approach to the musical material, where there is space for color, dynamics, depth and thought. This is a presentation which on the one hand is unmistakably a pleasant and non-invasive, and the other says a lot about the recordings – it tells listeners mostly about their advantages using mainly superlatives.

Because the presentation breathes, has proper momentum, and tonal richness – these are all elements that are most often mentioned as the distinctive features of hi-res files. In my opinion, more important, however, are some other things more concerned with music than with hi-fi. It's a sound that features all traits of a high sophistication, which has a beautiful depth, sensitivity to smallest elements that hide "under" the sound, without emphasizing details. This is, I believe, an intrinsic feature of DSD format – there is little selectivity and a lot of resolution. It is difficult to point the leading edge of the sound, and so instruments are clearly not "cut out" from the background.

Listening to this DAC I confirmed what I heard with the best SACD players I auditioned, including dCS Vivaldi and 900/901 Accuphase system and which - I believe - so fascinates many sound engineers, reviewers and music lovers. The sound that you get with high-end devices that support the DSD signal (either from a file or from DSD and SACD discs) is incredibly fast. It resembles a live sound in this regard. One can not feel any blur of the attack. Subjective relaxation goes hand in hand with perfect focus, which translates into a distinct signature of sound's "presence". It has real weight, size, it is dense. It all produces an outstanding dynamics, especially on the micro scale. All other recording systems, except for to analog tape recorders and truly top level digital systems, compress the sound and slow it down. They add to the sound an artificial richness that is supposed to mask that. But this is only a trick to full a listener.

The reviewed DAC proved that it can be done in a much better way for relatively, considering true high end level, low price. DSD files with jazz music from the 1950s and 1960s, and then some new projects, such as, for example, Dead Can Dance and Dire Straits albums, sounded in a concrete, focused way. They were open, but rather towards inside than outside, ie. they did not emphasize treble. Treble with Tube DAC DSD is always smooth, but it's not what I meant – it's about an abundance of information without explicit details. Every time I felt like participating in the show, in the event. The sound was incredibly rich internally, filled with music.

We all know that in audio it is always a "quid pro quo", so after all the praises come a downside. Amare does not play a powerful rock in such a convincing way as PCM systems and turntables. So it won't deliver properly punchy, focus and punctual bass and it won't add an aggressive attack metal cymbals and guitars. It simply is not able to do that. Its low bass is powerful and tuneful, but it lacks focus that would allow it to always control the sustained double bass' sound played of recordings that are, in this respect, often exaggerated. If the recording has a lowered tonal balance, the DAC tends to emphasize and deepen that effect. Usually without consequences, but sometimes there is too much "richness” in its “richness”. When bright recordings are played Amare does not make them any brighter than they are.

Summary

The Amare Musica's DAC make and finish is very good. It is obvious that it's a well thought-through design and not something created on impulse. And even if at its roots there actually was an impulse, it has been properly “digested”. Same goes for its performance. In physics every action causes reaction, and so in audio use of a certain solution changes the balance between elements, and it is not possible to achieve same level of presentation of all elements of the sound at the same time; unless it's a very low level one wants to achieve :) When a decision was made in Amare Musica to convert the digital PCM signal to DSD and to decode the latter in a passive system it automatically meant choosing a certain "package". It produces excellent results, but rather with high-resolution files, especially with DSD ones. It should be clear from the start, but it is worth making sure that ones realizes that before making a purchase decision. If CDs are preferred medium and one listens not only to classical and jazz music, this particular "package" may not be enough.

But if we you are music lovers and you want to get the most out of high-resolution files, the reviewed DAC can help you with that in a unique way, while not ruining your budget. It offers proper dynamics, color, fleshiness of the sound and the "shimmering" of the elements in the background, which gives an impression of listening to live music. This is, of course, only an approximation, but a very interesting and convincing one.

The Tube DAC DSD by Amare Musica is a compact, well built device. The front panel measures 440 mm – 2/3 of a classic rack width. Its chassis is composed of tightly fitting and nicely finished panels made of 10 mm thick aluminum. It features a front with beveled, in a characteristic way, sides, which makes it look like a cut diamond - hence the name of the series, this DAC is a part of, Diamond. The device sports four high quality Ceramic Disc Tablette feet made by Polish company Franc Audio Accessories.

Front and rear

The front features only two LEDs - orange and white. The first lights up after powering the device up with a mechanical switch on the back of the device and the other after tubes are ready. Besides these two LEDs there are no other indicators that would reveal synchronization with the transmitter or give up information on the sampling frequency of the input signal. It's part of an idea for a "maintenance-free" device that does not require user's attention. Also the the system that turns off the device after a certain period of inactivity is a part of the general approach, and it also prolongs tube's life.

On the back, in addition to a power outlet and on/off switch, they are also very nice Neutrik connectors – a digital S/PDIF RCA, XLR (there is a small selector to choose between them) and USB. These two are the first priority inputs, so if you want to play music through USB you need to turn off the CD transport (or other source) with a digital signal, or pull the plug from DAC's input, which is not a very convenient solution. Unless of course a computer or music server are the only source you use via USB output, then there is nothing to worry about.

Inside

The power supply and the analog section were assembled on a large PCB, and two smaller ones, with digital circuits are bolted to this main one. The transformer preceded by a mains filter are separately screwed onto the bottom of the enclosure. The transformer's housing is filled with a vibration damping material. The transformer features four secondary windings, separately for tubes' anode voltage, their filament and for low voltage electronics. All of them, including the filament one, are regulated by systems using Nichicon capacitors.

The USB input is supported by Atmel microcontroller featuring two high quality oscillators. It seems that this PCB was purchased from an external supplier. Beneath there is a slightly larger board, with AKM AK4137 chip, which converts PCM signal to DSD. Next to him there is a secondary Atmel chip. RCA and XLR inputs are supported by digital receiver, Wolfson Microelectronics WM8804. Both are galvanically isolated using small impedance matching transformers.

A passive system that converts DSD digital signal to analog and the 1st order analog filter sit on the main board – these are Wima precise, non-inductive resistors and capacitors. The output signal is amplified and buffered in two double triodes per channel – the reviewed unit featured NOS 6H23П Soviet tubes, plugged into ceramic sockets with gold pins. But one can replace them with other, compatible with this model, tubes and thereby to obtain a slightly different sound. The output features high quality coupling capacitors, Mundorf M-Cap MKP, followed by relays, muting output signal. This is a very decent, clean solution.

The device is delivered in solid case with company logo on the top side. Amare Musica, as usual, prepared a refined, well thought-through device that sounds and looks really good.

Specifications (according to manufacturer)

USB input:
PCM: 44,1 | 48 | 88,2 | 96 | 176,4 | 192 | 352,8 | 384 kHz, all 32 bits
DSD: 11,2 MHz | 12,4 MHz | 22,6 MHz | 24,6 MHz (DSD64-DSD512)
Inputs RCA/XLR: 22,05 | 24 | 32 | 44,1 | 48 | 64 | 88,2 | 96 | 192 kHz, all 24 bits
Tubes: 2 x 6H25П per channel
Output signal (RCA/XLR): 2 V/4 V RMS/0 dB
Output impedance (RCA/XLR):180 Ω/360 Ω