TAD, short for Technical Audio Devices Laboratories, Inc. is a relatively young company, founded on October 1, 2007. But as early as 1975 its parent company, Pioneer Electronics set up a subdivision which was to design high-quality, technologically advanced speakers. That division, called Technical Audio Devices has been operating as a completely independent laboratory. As a result of technical development and created a lot of material published by Audio Engineering Society (see Robert Harley, An Overnight Success 35 Years in the Making, entry of November 9, 2011 “The Abso!ute Sound”; available HERE). It was that combination of large funds and brilliant engineering that resulted in designing the speaker drive cone made of beryllium.
However, we had to wait until the year 2000 when a separate company, Technical Audio Devices was set up and Andrew Jones was hired to run its RD department. He is an engineer previously working for many years for KEF, the person co-responsible for KEF’s greatest success, the coaxial Uni-Q speaker system.
Jones designed from scratch a new speaker, Model One, which became the company’s reference speaker and gave the company added momentum. Among the many technical innovations that the Model One could boast, one drew special attention – the Coherent Source system, a development of the Uni-Q, with beryllium cones in both the tweeter and the midrange driver. As Robert Harley mentions in his referenced article, a coaxial speaker system turned out to be something closer to Japan than the UK – that kind of design was patented in the late 70s by… Pioneer and TAD. Thus began an official, international history of the latter.

The C-600 preamplifier, together with the E1 speakers, is the latest device added to the manufacturer’s lineup in April 2012. This year’s High End show in Munich (described HERE; see photos 3 and 4) was among the first opportunities to see it and listen to it. I was sent for a review exactly the same unit that had been displayed in Germany. It is the very first C-600 in Europe. The preamp completes TAD’s top system, the Reference Series, which also consists of the D-600 SACD player and the M-600 power monoblocks,. Among the C-600 special features the manufacturer lists:

• fully balanced dual-mono design
• enclosure with absorption and vibration damping
• circuit optimized for the best signal to noise ratio
• high-quality components
• excellent functionality
• Extreme Link – to synchronize several C-600 preamps, creating a multichannel analog system (surround).

The current CEO of TAD is Mr. Yoshihiro Hirano.

ODSŁUCH

The C-600 looks, the manufacturer’s name and website with descriptions full of technical information all seem to suggest a “technical” sound. In other words, precise, accurate, devoid of “soul.” Maybe even “cold”. These assumptions are not without a solid foundation – in the past, solid state preamps sounded just like that. They usually offered excellent resolution and selectivity, but in return they sacrificed such qualities as plasticity and meatiness, the so called “presence.” The customer had to decide which sonic qualities were important, what he or she expected from the audio system, how the preamp should modify the sound, etc. For each preamp changes the sound, even if someone thinks it does not.
For some time, however, I have observed a paradigm shift, a major structural change in how audio designers approach the sound in general, and their designs in particular. As if finally they came to terms with the limits of technology, be that tube or solid state; as if the best of them managed to find the golden mean within a given paradigm.
For in terms of tone color the C-600 sounds like a good, modern tube amplifier. The color is very similar to that of the fully-tube Audio Research Reference 5 SE preamp (reviewed in the same issue of “High Fidelity”).
The main point is the total absence of any lightening or sharpening of sound. These characteristics are normally associated with solid state technology and have been the reason why many music lovers and audiophiles have eliminated solid state from their circle of interests once and for all. But perhaps it’s time to rethink these assumptions.
The C-600, which is a good example of this change, demonstrates sonic characteristics so far reserved only for tube devices. These are natural tone color, organic texture, large soundstage. But we also get familiar characteristics of solid state, such as contoured, excellent bass with low end extension and control, as well as the ability to organize the soundstage.
And it is that characteristic, i.e. proper ordering of what is shown between the speakers, which is the biggest advantage of the reviewed device. The TAD preamplifier is able to find order and internal rhythm hierarchy in literally every recording. In comparison, the Audio Research (in terms of that particular element) sounds somewhat messy. Even the Ayon Polaris III [Custom Version], my reference preamplifier, could not step into the internal structure of the recording with equal precision and it is only the Soulution 720 that did it on the same high level.

I think it’s due to remarkable ability of signal differentiation. I started my listening session a little differently, with an old album by Clan of Xymox, a re-edition of their debut album Subsequent Pleasures, from 1983, also including a demo recording of their hit album Clan of Xymox from 1984. All these recordings bear the mark of time, of very simple recording techniques, poor sound engineering and even weaker production. But, like any interesting music, they have that SOMETHING, which makes us listen to them with interest.
The Japanese preamp presented them really beautifully, and that’s because it somehow managed to put order into the chaos reigning in these recordings, to find their inner rhythm and a kind of “backbone” on which everything is built, to which everything refers. Moreover, the C-600 showed vocals particularly well, originally hidden deep in the mix, and showed by nearly all preamplifiers I know as melted with the background, with fuzzy contours.
That selectivity, order, etc. were not burdened with original sin which we have already mentioned – it was not done through lightening or sharpening the sound. Getting a little ahead of myself, I will say that TAD’s tone color could even be described as dark. Maybe that’s exaggeration, but it certainly is not bright, not garish.
Perhaps that’s why vocal-based recordings sound equally well. On the Clan of Xymox album it was a secondary quality, the selectivity of vocals was something “by the way,” because they do not constitute a central musical element (at least on this particular album). But with recordings by Beverly Kenney, Sarah K., Jorgos Skolias, Anna Jantar, Sigur Rós – agreeably a bit random selection, from completely different musical worlds – it showed itself as vocal stability, its sonority, its “weight” certainty for the listener. That quality is each time equally startling, and it puts accents somewhere else than do other, less capable preamps.

For the midrange is what’s most important here. It is from here that the treble extends to one side, very clean, very orderly, and the full and contoured bass to the other side. That contoured bass is another characteristic of this sound. And that’s also, finally, what sets the TAD apart from tube preamps – the Audio Research Ref5 SE and my Ayon.

Both tube preamps sound slightly softer, for better or for worse. The C-600 is contoured, without hardening the attack. It simply shows the mid and upper bass quite clearly, and that’s probably what makes it sound so rhythmic, so tight and organized. On the other hand, it gives it the character that determines its influence on the system.

And the bass extends really low. It is with comparison against the C-600 that most other preamps exhibit bass roll-off; they lose it somewhere and muddle the bass at its low end (as long as the speakers can demonstrate that…). The Japanese preamp extends the bass uniformly right down to audible frequency range. Recordings featuring double bass or bass guitar may not show specially clear. We experience it as part of rhythm and bass contour. However, with electronic music, with electronically generated very low sounds the C-600 will keep steady all the way down, to the last sound decay, to its “guts.”

As always, in case of such device, its sound is a collection of compromises. If you think that the top high-end is somehow different, that there are no compromises here, you are wrong.
The C-600, for example, does not sound so vivid, so palpable as the two already mentioned tube preamps. Especially the Ayon is able to show instruments in a more 3-D way, with better bodies, more “here and now.” The TAD treats all albums the same, ordering them and giving them top down structure. Regardless of the recording. By doing that, it makes different recordings sound more alike. Of course, that’s nothing terrible as, for example, the Audio Research unifies the recordings by giving them a specific color, but it is still a departure from pure neutrality.
And these are perhaps the only two characteristics that can make us spend the money elsewhere. Not for sure, because that’s still a matter of choice, but there will always be listeners for whom these two elements – the unification of recordings and the resulting distance from absolute naturalness – are more important than any others. Apart from that, the C-600 is a great example of an absolutely top preamp, which does not have the “solid state” tone color. It has its own distinct character, but in a blind test could easily be taken for a tube device. Operating it is a pleasure and it is very well designed. Its developers thought through every last detail. It is a real top high-end with no ifs, no buts and no quantifiers. It just is.

Testing methodology
The Soulution 720 was compared against my reference preamp, the Ayon Audio Polaris III [Custom Version], as well as other linestages reviewed for this issue of “High Fidelity”: the ModWright LS 36.5, the Audio Research Ref5 SE, the Avantgarde Acoustic PRE, the Octave Jubilee, and direct coupling of my Ancient Audio Lektor Air V-edition CD player and my Soulution 710 power amp. The 720 drove two power amps – the above mentioned Soulution 710 and the Leben CS-1000P. It was connected to the AC mains by the Harmonix X-DC350M2R Improved-Version power cord and sat on its own feet on the Base IV [Custom Version] rack.
The testing had a character of A-B comparison with A and B known. Music samples were two minutes long. I also auditioned whole albums. Coupling was via RCA unbalanced cables – both on the source and the power amp sides. Despite the fact that the preamp has XLR balanced inputs the audio circuit has – according to description – unbalanced topology. Coupled via RCA cables it sounded better than via XLR cables.
It’s important to properly warm up the device before auditions – an hour should be enough to stabilize the temperature and the parameters of active amplification and power supply components.

DESIGN

The C-600 from TAD is a solid state linear preamplifier, with an external power supply unit. The power supply externally looks the same as that used earlier in the D-600 SACD player, and it resembles a Darth Vader spacecraft – black, angular and solid. The C-600 is not a big device; however, it is very heavy. The reason is that a lot of design ideas went into solving problems with vibrations that deteriorate the sound. That is why the unit sits on a solid platform – an aluminum plate 33 mm thick and weighing 15 kg. The bottom plate is finished in black structural lacquer; other enclosure sides are made of sanded and anodized aluminum in natural color. The whole unit stands on three aluminum cones – two in the front and one at the rear. Rear-mounted are two rubber feet, lower than the center cone. They provided additional support, should anyone lean on either rear corner. Simple and cool. Other panels are made of aluminum plates, with the front panel shaped characteristically in the whole “C” line from TAD – it has two planes, meeting at an angle right in the center.

Linestage unit: front and rear
The front panel sports two large control knobs – input selector and volume control. They have no starting or ending point, and so they only serve as en-encoders. The knobs are mounted on solid, 41 mm roller bearings, providing a sense of operating a solid device. In the center we have a large, easy to read (hooray!) characteristic amber display. We can read out various settings – in daily use these will be the selected input and volume level. On both sides of the display we have buttons covered by common plates (somewhat retro, 70s style). Pressing the symbols activates given functions. You can access and exit the menu, enable or disable the display, activate the Mute mode or change volume control stepping – you can choose between 1 dB and 0.5 dB steps. The rear panel looks equally interesting. It is divided into two parts, one for each channel. They are separated by large, multi-pin twist-lock connectors for the umbilical cord to the external power supply.
There are six inputs – three balanced XLR Neutrik connectors and three unbalanced RCAs looking the same as those in Accuphase or Marantz devices. There are also line outputs – as many as four pairs! Two are balanced and two unbalanced. You can also use two (XLR - RCA) fixed level line outputs, e.g. as monitor loops or for connecting a headphone amplifier. They are combined in monitor loops to inputs no. 3 and 6. Inputs 2 and 5 can be selected in the menu to have “unity gain”, i.e. 0 dB gain. They can be used as pass through for an external home theater processor. Note that in the menu you can also set gain individually for each input.

Linestage unit: interior
To get inside you need to remove the 12 bolts securing aluminum heavy plate. After removing it reveals to our eyes a very nice view - the interior is neatly divided into two parts by means of a “tunnel” running through the center and housing power connections. At the front we see a carefully shielded PCB with a control microprocessor, powered by a separate supply. Gain stage is spread on two PCBs – a large PCB with power supply, input selector, volume control and input gain stage and a smaller PCB with output stages.
Audio signal is routed in a very unusual way. Initial buffering and pre-amplification is carried out in separate paths, for each input separately. RCA inputs sport balancing circuits, and Burr Brown OPA2134 and other ICs for signal gain regulation to even out the RCA and XLR inputs. The signal is then coupled via large, foil capacitors bearing the TAD logo to volume attenuator built on an IC and a resistor ladder, also with the TAD logo. And then the signal goes to proper gain stage. It is based on large complementary pairs of the 2SA1859+2SC4883 transistors from Sanken. They are mounted on sizable heat sinks. Interestingly, each channel sports eight transistors, separately for the RCA inputs section (the signal leaves that section in a balanced form) and the XLR section and – it looks so – separate for each input. Hence, there is no parallel connection of inputs – each of them has its own gain path! After the gain section the signal goes to the upper PCB with outputs switched by relays from Takamisawa (the input selector is also relay-based) and via coupling capacitors to output connectors on the rear panel. The coupling capacitors are shielded with copper plate.
Another copper shield separates gain stage transistors from the power supply section. For even though the supply voltage is rectified and filtered in the external power supply unit, the rest of filters and voltage regulators is located here, next audio circuits,. We can see large capacitors with the TAD logo, manufactured by Nippon Chemi-Con, as well as Nichicon Muse and Elna Silmic capacitors. It’s obvious that they were selected through listening tests – each section sports a slightly different set. The manufacturer draws attention to the extremely short signal path – apart from volume attenuator there is only a single gain stage.
The whole design is of highest order, although it needs to be said that the signal partly goes via shielded cables, coupled to PCBs with pins and plugs.

Linestage unit: remote control
Remote control has metal top and plastic bottom finished in such a way that it fits nicely in the hand. There are not too many buttons and those present are logically separated into two sections. The remote, as probably all remotes in the world, is made in China. The whole preamp is manufactured in Japan.

Power supply unit
Power supply is housed in a very heavy aluminum enclosure. It is very stylish, finished with black structural paint. The front panel only sports a single blue LED, the rear two DC power connectors for the linestage unit, an IEC socket, and a mechanical power switch. The entire enclosure is made of thick aluminum plates.
The interior shows a picture associated rather with high-end amplifiers than power supplies – a massive 400 W toroid transformer and two PCBs – input and output. The input PCB sports large ceramic fuses and an AC filter. The top PCB houses three voltage rectifiers and power filters. That section, let’s call it “noisy,” is separated from the other “clean” section with a copper plate. The clean section houses a bank of large filter capacitors with the TAD logo, same as those in the linestage unit. They are bypassed by smaller foil capacitors. The PCB is marked as “Manufactured by Little Fuse Inc.”