People from Human Audio are not easy to reach. Even though it was them who came up with the suggestion to test this combo, i.e. a CD player with a digital input and a USB-S/ PDIF converter, later on I had a hard time to contact them about the specifics (time, postage, etc.). The system arrived with no manuals and there are no manuals on the manufacturer’s website either. In that respect, then, at the beginning I had to rely on Srajan Ebaen’s text from “6moons.com” who apparently had been more fortunate. He quotes fragments of e-mails from our (i.e. Polish) Hungarian brethren (see HERE) which turned out to be helpful.
That’s right, I could not resist not to recall the connection between our two countries A couple of days earlier I saw on the news that in the Polish town of Namysłów a statue of the king Stefan Batory was erected, donated by Hungarian partner-city – Kisköre (see HERE) and a day earlier I had my weekly stroll with my daughter and visited Kraków’s cathedral where the remains of Batory are buried and his tombstone erected (see HERE). Well, despite the fact that expensive Tokajs are more than just a wine for me and despite frequent references to Hungary in Poland, communication with Human Audio was a bit of a problem.
I put it down to them being overloaded with work, though. I am familiar with a lack of time of Jarek Waszczyszyn, the owner of Ancient Audio, and how hard it is for him to find a while to get away and talk, even though we both live in Kraków and roughly half an hour bus drive apart. I can relate.
It was even easier to forget the nuisance as after a while the communication channels opened and a manufacturer’s representative, Krisztian Neukum, turned out to be more than helpful in providing both specifics of the combo as well as their “background”.

I recalled Jarek and Ancient Audio not without a reason. Next to our Hungarian king (his Hungarian roots being equally important in my country as the fact that he was a good king of POLAND) and a certain common affinity for drinks and swords another link between our two nations is a similar design idea for a CD player, shared by both Jarek and Human Audio people. The player is a top-loader which is not strange at all, except for the fact that the CD here is totally exposed.
The concept itself was almost simultaneously conceived (as far as I know; if not correct me, please) by Polish Ancient Audio and Japanese 47 Labs of Mr. Kimura. Picked up later by a score of other manufacturers it has become public property. The fact people from Human Audio benefited from. As can be gleamed from Srajan’s review the company started around 2010 – Mr. Neukum (signed as Chris in e-mails) wrote that they had started “quite recently” and the test was published in January 2011 (the Libretto player). Later sent materials were more specific stating their première was at Home Cinema & HiFi Show in WestEnd Hilton Hotel in Budapest in 2010.
Even then, the company offered thoroughly thought through products, where the most important purpose was to clear the signal from all types of noise generated by power voltage. After a number of trials the conclusion was that the voltage from conventional home power networks has to be completely separated from the devices. Nothing serves better here than the battery. Mr. Krisztian Neukum, the head of sales of Human Audio explained that to me in his e-mail as follows:

"In the course of our search we could not find solution equal to pure battery power. Hence our conclusions and research and in effect – battery power as a part of our devices.”
And then:
“The Libretto HD has got separate batteries for digital and analog sections, powered directly with no DC/DC converters to increase voltage. A small charger for the batteries is not a part of the device but is outside. For that reason the power voltage is never in the proximity of the player. Even the charging process is active only when the player is switched off. With the batteries fully charged the Libretto HD can run for 24 hours without charging.”
And a bit later:
“Soon we plan introducing an optional, solar charger which will allow us to rid completely of power grid at home.”

The last statement is particularly interesting – next to an ultra-clean power it is also an expression of a modern approach to the environmental issues presented by Human Audio, which is frequently referred to in the company philosophy. Krisztian Neukum himself addressed the issue a couple of times in his e-mails stating that protecting the environment is one of the more important issues when designing their devices. Solar energy is one thing, the other being materials used for housing CD players and an amplifier (with power supplies). Human Audio uses solid bamboo for housing, a very fast growing grass (the bamboo is actually grass, not a tree), which can be regrown in almost no time at all.

As is the case in well thought through designs that is not the only thing that matters. I do believe that equally important for HA people was the fact that bamboo is really a superb looking material which lends its look in turn to the devices it houses. Before I had the chance to see it myself, the Libretto HD looked really cool on the photos. After I took it out of the well-designed box, after I placed it on the shelf I realized its aesthetic value and how much energy (renewable energy, vital energy of a human being) has been put in exterior design of the reviewed devices. That part of the process was not left to chance either. The person responsible for the components’ look was Mr. András Göde – the head of Kroki design company.
The company itself is not a big one and its members are:
András Göde: exterior design
Attila Juhász: tests, consulting
Peter Büdszenti: research, tests, prototypes
Krisztian Neukum: sales, production, quality control<.p>

Apart from the player there came the Tabla USB-S/PDIF digital-digital converter. This little box, battery powered via USB cable, employs M2Tech modules (we reviewed their system HERE) i.e. an XMOS chip. It supports sampling rates from 44.1 kHz up to 192 kHz and works in asynchronous mode clocking the signal independently from the computer.

SOUND

A selection of recordings used during auditions: CD i SACD

• Ash Ra Tempel, Ash Ra Tempel, MG Art/Belle, 101780, SHM-CD (1971/2010).
• Assemblage 23, Bruise. Limited Edition, Accession Records, A 128, 2 x CD (2012).
• Carol Sloane, Little Girl Blue, Sinatra Society of Japan, XQAM-1036, HQCD (2010).
• Dead Can Dance, Anastasis, [PIAS] Entertainment Group, PIASR311CDX, Special Edition Hardbound Box Set, CD+USB drive 24/44,1 WAV (2012).
• Depeche Mode, Enjoy The Music....04, Mute, XLCDBONG34, maxi-SP (2004).
• Depeche Mode, John The Revelator, Mute, LCDBONG38, maxi-SP (2006).
• Hilary Hann, Bach - Concertos, dyr. Jeffrey Kahane, Los Angeles Chamber Orchestra, Deutsche Grammophon, Universal Music LLC [Japan], UCCG-50058, SHM-CD (2003/2011).
• Hilary Hann, Hilary Hann Plays Bach, Sony Classical, SK 62793, Super Bit Mapping, 2 x CD (1997).
• J. S. Bach, Sonatas & Partitas, wiol. Henryk Szeryng, Sony Classical/Sony Music Japan, SICC 840-1, 2 x CD (1965/2007).
• Jean-Michel Jarre, Magnetic Fields, Dreyfus Disques/Epic, EPC 488138 2, CD (1981/1997).
• Monserrat Figueras, La Voix De L'Emotion, AliaVox, AVSA9889A+B, 2 x SACD/CD (2012).
• Simone Kermes, Viva!, Archiv Production, 477 9843, CD (2007-2008).
• Tadeusz Woźniak, Tadeusz Woźniak, MUZA Polskie Nagrania/Polskie Nagrania, PNCD 1289, CD (1974/2010).
• Ultravox, Vienna, Chrysalis/EMI, 23436527, Remastered Definitive Edition, 2 x CD (1981/2008).
• Vangelis, Spiral, RCA/BMG Japan, 176 63561, K2, SHM-CD (1977/2008).
• Yo-Yo MA & Bobby McFerrin, Hush, Sony Music/Sony Music Hong Kong Ltd., 543282, No. 0441, K2HD Mastering, CD (1992/2012).

Audio files

• Assemblage 23, Rain Falls Down WAV 16/44,1 [z:] Bruise, Accession Records, A 128, Limited Edition, 2 x CD (2012).
• Audiofeels, Sounds of Silence, WAV 16/44,1 [z:] Audiofeels, Uncovered, Penguin Records, 5865033, CD.
• Bob Dylan, Blowin' in the Wind, WAV 16/44,1 [z:] Bob Dylan, The Freewheelin', Columbia/Mobile Fidelity, UDSACD 2081, SACD/CD (2012).
• David Sylvian, World Citizen (I Won't Be Disappointed) + Angels, WAV 16/44,1 [z:] David Sylvian, Sleepwalkers, P-Vine Records, PVCP-8790, CD.
• Dead Can Dance, Anabasis, WAV 24/44,1 kHz [z:] Dead Can Dance, Anastasis, [PIAS] Entertainment Group, PIASR311CDX, Special Edition Hardbound Box Set, CD+USB drive 24/44,1 WAV (2012).
• Kankawa, Dear Myself, 24/192 WAV [z:] Kankawa, Organist, T-TOC Records, UMVD-0001-0004, Ultimate Master Vinyl, 24/192 WAV; review HERE.
• Keith Jarrett, January 24 1975. Part I, WAV 24/96 [z:] Keith Jarrett, Köln Concert, WAV 24/96, HDTracks..
• Me Myself And I, Elytom Encon, WAV 16/44,1 [z:] Me Myself And I, Do Not Cover, Creative Music, 005, CD (2011).
• Pieter Nooten & Michael Brook, Searching, WAV 16/44,1 [z:] Pieter Nooten & Michael Brook, Sleeps With The Fishes, 4AD, GAD 710 CD.
• Sonny Rollins Tenor Madness, WAV 24/96 [z:] Sonny Rollins, Tenor Madness, WAV 24/96, HDTracks.
• Stan Getz & Joao Gilberto, Corcovado (Quiet Nights Of Quiet Stars), WAV 24/96 [z:] Stan Getz & Joao Gilberto, Getz/Gilberto, WAV 24/96, HDTracks.
• The Alan Parsons Project, Sirius + Eye In The Sky, WAV 24/192 [z:] The Alan Parsons Project, Eye In The Sky, DVD-A.

Japanese editions of CDs and SACDs are available from

Libretto HD as a Compact Disc player
Listening to the Hungarian player in the company of the Lektor AIR V-edition from Ancient Audio (see HERE) gave me a good insight into what is going on with the Libretto HD. The cross comparison with the exceptionally well made and similarly priced Marantz SA-11S3 with an onboard DAC, asynchronous USB input and based on the latest Tenor chip (24/192) allowed me to somehow place the sound on my personal ladder.
Above all I have to say that it has a very similar character of music making to my Lektor. Very pleasant vocal textures, expansive sound stage, splendidly exposed tonal differences. The Libretto HD is smoother in midrange than the Polish player, more sort of “lingering” and, in a sense, “warmer”. It is not as warm as e.g. vocals presented by another Polish player based on tubes and TDA1541 DAC from Philips, the Nirvana from Dubiel Accoustic (see HERE). The Nirvana is unequivocally warm and without inverted comas at that. There it was the choice of D/A converter and using non-oversampling design as well as particular choice of output tubes that emphasized a part of bandwidth. A tube based power supply played no small part either. Here the result owes to the battery based power supply and output transformers. I am sure of both of these things but I lean to a belief that the power supply is the chief “culprit” here.
It is not classic “warmth”, though, which is usually due to coloration. After all, emphasizing any given frequency band is really coloration, no matter if we like the result or not. In the Libretto HD player it is a derivative of much smaller distortions, not of fiddling with the linearity of musical range. I have seen that in other high quality devices and it has always been the same story: we reduce distortion to a really low level taking care that what’s left is of even-order nature and the result is similar to the reviewed player. This is really a great scenario! And so difficult to achieve at that – it’s easy to say “reduce distortion” especially while we have – as is the case with the Libretto HD – zero-feedback analog output stage.
It is evident, though, that the result can be achieved by “cleaning” power supply. I know that not only because I had a chance to listen to Ancient Audio players with different power sources but also because I am aware of the effects different power cords and power strips have on sound. The former have little or no effect with the Libretto HD as the device is powered through a battery based power supply charged via an external charger. .

It must be said that battery power leaves its signature on the sound of such powered device. No doubt about it. You can, of course, screw it up as the next thing as it happens now and again since battery power has its limitations and idiosyncrasies which are difficult to explain (for instance changes in sound when using power cells of different design) but it can prove to be something special as well. You can’t probably eat a biscuit and have it; it is possible, though, to fine tune certain aspects of sound to such perfection that you can die happy…

In the Libretto HD it’s all about the already mentioned smoothness and “lingering” of midrange. This range is incredible and listening to records with violins, like for example Hilary Hann and her Bach Partitas or her beautiful Bach Concertos issued by Deutsche Grammophon was a deeply satisfying experience. The sound was expansive, with panache and slightly forward midrange.
Yet it’s not unequivocally “such” or “such” sound. It’s sufficiently complicated internally and multithreaded to escape a simple description. Tonality is set a little higher than in the Lektor AIR V-edition but lower than in the Marantz SA-11S3. Bandwidth seems to be less extended in both directions than in the Lektor, particularly in the lower end. This last statement asks for a few words of explanation. The Hungarian player is not “light” by any means, it does not sound dry, heavens forbid. Comparing with the majority of digital players it would seem to have more body (certainly more than the Marantz). It is simply because the Polish Ancient is exceptional in that respect and only the Solution 745 SACD player (see HERE) could achieve a similar feat. The Libretto HD sounds powerfully, the sound is full and low but it can still be improved. I am not talking about simple “bass extension” or “weight” for all of that is here as it should be. I am talking about saturation and differentiation of that range.

Let me give an example. I conduct my tests in my apartment in a small block of flats. The block is in an extremely quiet part of Kraków; not too many neighbors around with the majority of them at work during the day (working to pay off their mortgages). So, I don’t particularly worry about the volume I listen to. With an honorable exception of my down-floor neighbor Mr. Adam Ziemianin. Playing something with a stronger bass beat is kind of stressful to me because without my knowledge I might be meddlin’ in or disruptin’ the process of a new song being begotten. What if I am interfering with the creative process of an author of lyrics of a well-known Polish folk band SDM? And I am ignorant of this… Mr. Adam has nothing but a nice smile for me, he has never even as much as mentioned to me that I might have ruined his work flow, that the rhythm due to me is not the one, but…

I am particularly self-conscious while playing the new Dead Can Dance album Anastasis, and more precisely track no. 2 Anabasis with a powerful long decaying drum (kettle drum?). The Lektor presents this drum powerfully, low, with saturated color. Does not elongate it nor make it shorter; everything sounds long enough to create kind of a framework for the whole track. The Libretto HD presents it strongly, the instrument is full bodied but it decays faster and does not have that many details and aliquots as with the Lektor. The difference might not be that big, the Marantz and most of other CD players have an even more shallow presentation and simplify the sound further, but it is there. With the Polish player I was sure that Adam Ziemianin was seriously thinking of moving out, while the Hungarian player could only convince my neighbor to reach for a glass of something with a kick in it…

I would like to go back to what is most important in this player – to dense, pure midrange. Its balance is set a little higher than that of the Lektor – I think I have already mentioned that. Despite that, when we play on the Libretto HD small jazz bands, classical – preferably chamber – music, folk etc., it seems that midrange is incredibly warm and deep. Taking it apart into elements we come back to what I just wrote, with lesser selectivity and less of breath, less conviction of being THERE, yet the weight of presentation in some self-contradictory way is a result of merging all of this, as if resolution which is absolutely superb in midrange was pushing everything in the listener’s direction, as if it was revealing better PRESENCE of each sound and sound plane, etc.

And since we mentioned sound planes – the sound stage of the Hungarian player is just lovely. Foreground is quite close to us; it is not aggressive but states its presence here and now. The more distant planes are somewhat drawn forward, there is no such “extension” as with a good analog or the best digital but it is very good indeed. And all because the intensity of presentation distract our attention from what I stated above.

Libretto HD jako DAC + Tabla
I don’t know if you remember what Srajan Ebaen once wrote in one of his reviews – for him the CD is done with so if a CD player does not have digital inputs then he, Srajan, refuses reviewing such. For exactly that reason he did not review the superb Passeri player from Singapore manufactured by Loit (see HERE). Because he understands, though, that others, such as me, could hold to a different opinion, he published on “6moons.com” (see HERE) the review which had been published earlier in English in “High Fidelity”. He had no such problem with the Libretto HD. Calling devices such as the Libretto HD or, mentioned earlier, the Marantz SA-11S3 “players” is probably an anachronism. I had no idea myself which road it was going to take and for a long time I assumed that CD or SACD players with digital inputs were just that – “players with digital inputs”. Now I see that this position cannot be held onto any longer and it is time to verify that. Adding digital inputs to a digital player (of any type, because it is also valid with audio file players – see the Cambridge Audio Stream Magic 6 that I reviewed for “Audio”) results in it no longer being just a player but becoming (also) a D/A converter. Hence, in my opinion, manufacturers calling their devices CD/DAC or SACD/DAC describe them correctly. I still do not acknowledge terms like ‘CD/SACD’ cause they are illogical and misleading. Each SACD is also a CD player. In any classification a broader term that includes a narrower one becomes the superior one. Nobody of a sound mind would say “Blu-ray/CD player”, would they? Playing CDs is intrinsic to the BD format as well as to SACD.

Sitting, then, in front of the Libretto HD we deal with a multifunctional device. Although we have one digital input only, hence our options are somehow limited, yet it should be enough for most applications. We could connect an audio file player for instance, or a USB to S/PDIF converter and play the music directly from a computer. For those who want to do just that, the manufacturer prepared the very interesting Tabla converter, based on the circuit employed in the M2Tech, supported by a proprietary battery power supply (on the M2Tech system see HERE). Exactly that system, i.e. the Libretto HD as a DAC plus the Tabla with the proprietary S/PDIF umbilical terminated with BNC terminals, I had for a review.
After downloading and installing a driver (from the M2Tech website) in a dialogue window on the computer we can see an information ‘HiFace 1.0.3 Usb to Spdif (44.1 Khz – 192 Khz)’ confirming the provenance of the USB receiver. After just a few tracks the difference between the same album played from the CD and its digital version was evident, whether FLAC or WAV (in that case I could not tell big differences between those two codecs).
First of all, audio files sounded in a bigger, more tangible way than their “physical” versions. They were more spectacular and virtual sources were bigger and closer to the listener. That can be appealing, no doubt about it! If someone holds to the conviction that digital sound is conservative or even sort of lifeless, the Tabla can present a completely different face of the sound – unrestrained, dynamic and active.
What’s interesting it was especially true with CD quality audio files (I am talking about the specifications not the recording quality as that may differ) not hi-res. The latter were presented with more care; they were more vivid (paradoxically) and had more breath. They were closer to what we know from vinyl. CD files had emphasized bass which somehow lacked control. The already mentioned Anabasis by Dead Can Dance with its drum was slightly bigger than it should be, the drum lacked a definite moment of decay. Higher midrange was a bit stronger than from CDs. But precisely those anomalies were the reason that the sound was so unrestrained and expansive. And midrange (below 800 Hz) was even smoother, “warmer” than with the same records played from the Libretto HD. The Tabla is a fine, interesting converter with a distinctive character of presentation, especially with audio files of CD quality.

The Libretto HD is superbly made and the design is just fantastic. Both of these things put it significantly higher in my hierarchy than the Lektor AIR V-edition which I use on a daily basis. All those little details, like more intuitive disc loading, beautiful design etc. It also sports a digital input, the feature long announced by Ancient Audio that never saw the light of a day. On the flip side is a too small display, at least for me, and the lack of information about digital signal parameters, not even whether the input is synchronized or not.

The sound is so exceptionally smooth and saturated that it seems warm but really is not – the sound is too pure, too polite. Tone is great although set slightly higher than in my Lektor. Both space and differentiation, particularly of bass and treble, are better in the Polish player.
When both these sources stood side by side for two weeks, both on the Acoustic Revive RAF-48H platforms, I could choose whichever I wanted and when I felt like listening for pleasure through my headphones I usually settled with the Libretto HD. This device appeals to my aesthetic. I could additionally listen to music from my computer without having to use an external DAC, which was a nice bonus. The Tabla was very helpful here, a cool device with evident sound signature which would not appeal to seekers of truth at any cost. The sound of the Tabla is modified in such a way as to avoid any references to digital origins of the played audio files. Late at night, though, I couldn’t care less, enjoying beautiful, expansive sound from my files, particularly those in hi-res. Despite all that I can’t deny the fact that the Lektor AIR V-edition presents slightly better differentiated sound and that its tonal balance is set slightly lower which makes it a better partner for my “big” system with speakers. The Lektor’s soundstage is unbeatable and only the best turntables could compete here. If I had to choose between those two I would have a problem indeed.

The Libretto HD player was compared to a reference player i.e. the Ancient Audio AIR V-edition as well as to the Marantz SA-11S3 SACD player. A separate reference point were two turntables – the AMG Viella V12 and the Pro-Ject Expression 10.
The player sat on the Acoustic Revive RAF-48H platform, same as the reference player. The platforms sat on the top surface of my Base http://www.baseaudio.pl IV Custom rack.
Testing had a character of A-B comparison with A and B known. Music samples were 2 minutes long; whole albums were also auditioned. The player was connected to a preamp via the Acoustic Revive http://www.acoustic-revive.com RCA-2.0PA interconnect.

DESIGN

Libretto HD
Libretto HD is a top-loaded battery powered Compact Disc player with a D/A converter. The device is divided into a “clean” and “dirty” section. What is unusual though is that the “clean” division houses all audio circuits including the CD drive, the other one houses power supply i.e. batteries as well as the display with all the controls. It takes a while to get used to it but we soon realize that it is the only sensible solution and that everybody else got it wrong. Human Audio cannot claim the idea, tough, as I have seen it before in VTL http://www.vtl.com preamps. Both modules have bamboo made enclosures; one is almost tempted to say “wooden” but the bamboo is a type of grass not wood.
The drive section is similar to what we can find in 47 Labs and Ancient Audio devices – the disc is completely exposed. In order to listen to music one has to place the disc on the drive spindle, press the button to read the disc TOC (Table Of Contents) – traditionally done by a micro-switch in the tray – and voila. I happen to forget about the button in my Ancient Audio which can be irritating – the player displays information as if it was already done except that it is the info of the previously loaded CD. The Libretto HD has a more elegant solution. The player recognizes whether the disk is loaded or not. After the disk is removed the little red light next to the TOC button illuminates and leaves no doubt as to your future action.

Similarly to the Polish player one can see the drive spindle with its characteristic “mushroom cap” end to receive the disk weight as well as optics through the cutouts in a metal element that adds to the rigidity of the top of the enclosure. Unlike in the Lektor, the one in the Libretto HD is made with much greater care. It is milled of solid aluminum with an engraved logo, rigid and elegant. Disc weight is also aluminum, needless to say, nicer than the one in my Lektor player.

The rear panel sports high quality output and input connectors (from Neutrik?) – analog XLRs and RCAs as well as a digital BNC. There is also a multi-pin, gold-plated socket for an external power supply and controller.
The transport does not have traditional feet; it sits on the LIBRA decoupling platform from Hungarian Audio Libra. This is a “rigid” base utilizing a similar principle to the Ceraball anti-vibration feet from finite elemente and the Ceramic Disc from Franc Audio Accessories. It consists of three parts. The first is a glass plate with three concave sphere sections placed on the triangle plane. Steel balls are placed in the spheres’ centers and the transport sits on them, resting on three round glass plates attached to its bottom.
As I said, it is a “rigid” platform – people from Human Audio follow the same mental process as other designers whom I keep in high regard. To the ones already mentioned I would add Ken Ishiguro from Acoustic Revive – all of them consider this the only sensible way of coupling. People subscribing to that point of view consider flexible coupling unacceptable as it hides the problems instead of solving them. I will only add that this is a worldwide concept as it is applied in Japan, Germany, Poland and Hungary.

Inside we can see the Philips CD-Pro2 LH transport mechanism which is coupled to the bottom of the enclosure with metal bolts. Under the drive there is a big PCB with a smaller one directly above. Both are coated with some black vibration-absorbing material that also hides the details of the components used. The only thing you can spy is that there are two D/A converters, one for each channel, and that I/U conversion (I think) is based on ICs while amplification and filtering is built on JFETs. Output coupling transformers rarely seen in CDs are from American Jensen. Output stage works in class A with zero feedback. What draws our attention are strips of a very soft material glued in many different places, on PCBs, amplification components and around the relay.

Power supply/controls
Power supply looks similar to the player while being taller and much heavier. The reason for its weight is the fact that it houses two separate, big batteries – one for digital section and transport and the other one for the analog section. It also sports a display, transport mechanism controls and an infrared sensor. The display is a small, green dot-matrix type with two lines one above the other. After the CD is loaded it shows the word “Libretto” and the lower line displays total time. After pressing ‘play’ the upper line reads ‘disc’ with the time of the track below. One could use bigger digits! Twice as big in fact! Maybe an OLED display could do the job?
Next to it, we have got four toggle switches to control the transport and to switch the power. It is a very interesting solution, nothing like buttons. I took to it very easily. There is no button for input selection – e.g. a digital one. This function is moved to a remote where also sporting a button to switches off the display. The remote is also housed in bamboo and has only basic buttons – there is no direct access to tracks or a TOC button. We can turn the display off, though. After switching to a digital input the display reads ‘DAC mode’ – no additional information about the signal, whether it’s synchronized or not, what the sampling ratio is not to mention the word length. I consider it a serious overlook.
And finally a little LED visible through one of the glass discs under the power supply – if the light is green the batteries are fully charged. Red light means our playing time is soon over.

Tabla
The Tabla converter is housed in an aluminum-made enclosure with acrylic front and rear panels. The front sports two LEDs – green, telling us that the signal is coming and amber signaling the charging process. Charging only takes place when audio signal is off. When the converter receives audio signal, charging is switched off.
On the rear panel there is a USB input and an S/PDIF output with a BNC connector. Human Audio encourages strongly using digital cables terminated with such terminals. We were provided with one for our review.
The system is assembled on two PCBs. The smaller one is simply an M2Tech converter based on the Xilinx chip with two lovely clocks next to it, separate for the 44.1 and 48 kHz frequency families. There is one more for the input circuit working in a synchronous mode.
This board is soldered to a bigger one with the power supply system and two batteries. It sports very good Dale resistors, another clock underneath and Wolfson WM8804 chip. Interestingly, it looks like we have a digital receiver here with high jitter resistance which receives the signal from the USB-S/PDIF converter, recloaks it and sends outside. The output is transformer coupled. One can’t ask for more.